Conference vmszoo::rc

    
    	Most times people will buy smaller or different configurations
    of nicad packs. Most sailplanes that have two servos I have seen
    utilized a 250ma Rx battery pack. This is quite smaller than the
    std. 500ma packs. Most times they come flat. I suggest that you
    buy nicads either a 500ma pack in the square configuration or a
    250 ma pack in the flat or sqaure set up.  As an example I just
    bought two packs for different radio systems. I bought a flat pack
    as a replacement for an older pack to a futaba radio that was $17.95
    at a hobby shop and a 750 ma pack for use in my pattern ship for
    my JR radio. The 750 ma pack cost me $ 91.95 from Circus Hobbies.
    Their prices are somewhere between a distributers and a hobby shops.
    
    	I suggest that you go the nicad way rather than the drycell
    way. In the long run it will be cheaper.
    
    						Tom

    
    	Typo in the last reply. Price of the 750 ma was $ 19.95.
    
    
    						Tom

That brings up something I've got to get to.  My Astro .035 came
with a  flat pack; the damn thing drove me nuts fitting it into its
first plane.  I took the thing apart to put in an auto fuse, as
recommended by Mitch Poling in his book on electrics.  Anyway, the
surgery showed that the pack is composed of little 800 mA cells tied
together in sausage fashion.  At the time I just put the thing back
together and tried to stuff it into the little airplane.  Very
frustrating.   Next project, a Watts Up powered glider that's on the
board now, I'm going to take that pack apart and re-string the
sausages in a row of 3 with a row of 2 tucked behind (or on top).
Then wrap the mess with electrical tape -- shrink wrap would be
better, but not available here.   Since the construction of my flat
pack is probably similar to the others; that is, a sausage string of
batteries, this could be a fix for the flat pack problem.  Thing I'm
concerned about is to be careful not to short any leads while its
apart; those batteries pack a lot of wallop!

    
    	Be careful, some packs are welded rather that soldered.
    
    					Tom

>I have a square 4 AA cell battery and several Radio Shack nicads
>left over from the kids school projects. Can I use this assembly
>and charge it from my radio charger, or is there a mismatch that
>could harm one or both?

Sure - 4 Nicads in series are 4.8 volts - just what your charger
wants.  Also the Futaba radio charger is a trickle charger anyway
so it wouldn't matter if the cells were little or big.  Just let
it pump for 12-16 hours.

>	Another battery question. I got a Tower Hobbies Field
>Box, a power panel, and a 12v motorcycle battery for Christmas and
>was wondering. Do I need to add ventilation slots to the battery
>compartment, and should the compartment be lined with something is 
>case of a spill? 

I bought the Tower Hobbies box and power panel combo special last year.
I just painted the inside of the box with fuel proof paint.  No vents.
It never gets warm in there.  I had to screw the wires on the battery
cause the clips that came on the power panel would corrode and become
intermittent until I changed it.

I have to admit I've never held my box upside down to spill the battery.
If I did I would probably also dump glow fuel from the 1 gal can.

>Also, as far as charging, recharging the battery
>goes, can I recharge through the output terminals on the power
>panel or will I have to remove the panel every time I want to recharge
>the battery?

My panel was the "Pilot" black one with the connector to charge your Ni-Starter.
On that panel you can recharge from the output terminals.  It never said
so in the documentation - but I just followed the wires back to the battery
and there was nothing in series so I've charged mine several times thru
the output terminals.  I bought the banana clips from Radio Shack.

Speaking of banana clips - they have got me in trouble a couple of times.
Can't use my starter on other folks batteries because I cut off the alligator
clips.

Speaking of Ni-Starter charge connector.  That has saved me a couple of times
already.  Nice to be able to recharge your Ni-Starter at the flight line
in a couple of minutes. (Don't flame me folks - in two minutes it is not
fully charged - but it can start motors then and by the time you use up
that tank of fuel it will be fully charged.

By the way Dan.  How come all these questions about power and packaging?
You work in DEC's "Power and Packaging Group"! :-)

              _!_
Bye        ----O----
Kay R. Fisher / \
 
==============================================================

Yes, the gas buildup is a problem; it should be vented.  Better yet,
use a sealed gel cell.  I can't recall were, but I read just
recently that someone had an explosion from charging an open cell in
a closed compartment.  He commented that he had been doing it for
years and had never thought much of it till then.  He gave some
guidelines for charging an open cell battery; basically the same
precautions you use when giving a jump start.  Connect the positive
leads first, connect the negative lead on the dead battery, then
connect the negative lead to a good ground at the source, but AWAY
from that battery's terminals.  When disconnecting, remove the
negative leads first.  All this is to prevent sparks.  He also said
to keep the field box and charger well separated; something that
happens by default in a jump start.  In his case, the fuel in the
field box didn't go off.  I think he was only blinded for a short time.

================================================================================
Note 53.0                       NiCad Batteries                       18 replies
WILVAX::LATOUCHE                                     10 lines  13-DEC-1985 12:59
--------------------------------------------------------------------------------

Does anyone out there have info on NiCad batteries?

i.e...   recommended time for a full charge, discharging, average life
         span, problems to look for, affects from cold weather flying ???


thanks,

Jim

================================================================================
Note 53.1                       NiCad Batteries                          1 of 18
CLOVAX::COBURN                                        5 lines  13-DEC-1985 21:36
--------------------------------------------------------------------------------

The RC Modeller mag just had an article on the care and feeding of NiCads
about 2 months ago (issues I should say). Also I believe there is a note
in this file that is a similar discussion. Try a Directory of the file.

John
================================================================================
Note 53.2                       NiCad Batteries                          2 of 18
CRVAX1::KAPLOW                                       34 lines  15-DEC-1985 00:10
--------------------------------------------------------------------------------

I mentioned the affects of cold in my response #48.3 before I saw this note. As
I said there, the best source of this information is the nicad (not the RC
system) manufacturers data sheets. Somewhere down in my shop I have some of this
information, but it is not handy now (my shop usually looks like the aftermath
of a tornado, it is currently worse than normal). 

Briefly and without details:

1) Never short a nicad.

2) Never totally discharge a nicad.

3) Nicads provide a pretty constant voltage till they are nearly fully
discharged, then drop very fast. 

4) Nicads have memory problems. Do not run them down a little and then charge
them up. Pretty soon you will only get "a little" out of them. Best to run them
down to the hump on the curve (#3 above). 

5) Charge nicads at 10% rated capacity (ie 45 ma for a 450 mah pack) for 14-16
hours. Some nicads can be fast charged at 1/3 rated capacity for 3-5 hours.
Nicads left charged will lose power. better to leave them run down (not dead),
and charge just before using. 

6) Nicads can last as many as 1000 full charge / discharge cycles if properly
treated. Most aren't. "Your results may vary."

7) Problems include memory, cell reversal, and internal shorting. Some of these
are permanent, some can be cured to some extent. 

8) Cold kills. 

If you have any specific questions, I would be glad to try and answer them, as
time permits. Stick them here or send me mail. 
================================================================================
Note 53.3                       NiCad Batteries                          3 of 18
SAGE::KENNEDY                                        12 lines  16-DEC-1985 10:21
--------------------------------------------------------------------------------

This process of discharging the batteries to a specified level before
recharging is referred to as "cycling" the batteries. You can buy a
battery cycler for $20.00 - $90.00. depending on the features/flexibility
you opt for. You can purchase the least expensive type that simply discharge
to the appropriate level (not sure exactly what it is), then simply
sound a buzzer. At this point you would use the charger supplied with the
nicads to recharge. The fancy units allow for cycling of various sizes (500,
800, 1200 mAh,) and will discharge and automatically recharge the batteries.
Experienced modelers seem to agree that these units are well worth the 
investment for the protection and extended life they provide to the batteries.

-Mat
================================================================================
Note 53.4                       NiCad Batteries                          4 of 18
CRVAX1::KAPLOW                                        6 lines  16-DEC-1985 18:19
--------------------------------------------------------------------------------

Yup. I should have mentioned them. I don't own one myself, but ACE R/C makes
several, form simple to very fancy, either assembled or in kit form. Their kits
are pretty straight forward, but unless there is a significant difference in the
price of the kit, I wouldn't waste my time building them (particularly servo
kits). Their address was posted in another note recently. I have found them to
be a reputable company to deal with. 
================================================================================
Note 53.5                       NiCad Batteries                          5 of 18
FROST::RICHARDSON                                    20 lines  17-DEC-1985 08:27
--------------------------------------------------------------------------------

Good topic....  I have a "brand new" radio with few hours on it, and protecting
the ni-cads is a primary concern of mine.

As mentioned earlier, an issue of RCM had a short piece on care and feeding
of ni-cads.  If I remember correctly (which is anyone's guess at this point)
they also mentioned the practice of leaving your radio gear on after flying,
for long enough to substantially deplete the batteries.  This makes a little
sense, because you won't operate your radio until the batteries quit, unless
you like rebuilding a whole lot....  I don't know "how long" to leave the
radio on, but I would guess a quick computation or two using the drain rate
of the radio gear, the capacity of the packs, and the time you were flying
(or whatever), would tell you about how long it should take to wipe out
the charge in the ni-cads.  I guess stopping a little short of that point
would be the "best" way.

Is this a valid assumption?  I'm going to research it a but further, and
see what I can find.  Maybe giving up and buying a cycle charger would
be the smart move....

Eric
================================================================================
Note 53.6                       NiCad Batteries                          6 of 18
SAGE::KENNEDY                                        12 lines  17-DEC-1985 09:32
--------------------------------------------------------------------------------

Eric, the method of leaving your system on after use is not un-heard of.
Actually I know a couple of people in my club that do it frequently. However
all the material I have ever read on the subject (including manufacturers
sheets) indicate that letting the batteries go completely dead is harmfull
to the cells. And to stop the process, without accurate monitoring equipment,
at the appropriate time, seems unlikely. 

I have ordered a Ram Simple Cycler on sale ($16.00) from Tower. It simply
discharges and sounds an alarm. I will then use my existing charger. After
I have used it, I will post the results here. 

-Mat
================================================================================
Note 53.7                       NiCad Batteries                          7 of 18
FROST::RICHARDSON "Eric Richardson"                  52 lines  20-FEB-1986 15:17
                            -< More info on Nicads >-
--------------------------------------------------------------------------------

    Recently I ran across an article on battery selection, written by
    someone from Gates Corp.  The intent of the article was to provide
    information on nicads versus other forms of lead-acid batteries
    for various industrial and comercial uses.  Still, a few of the
    comments might be interesting, so I'll quote them out of context.
    If anyone wants a more detailed explanation on any quote, just let
    me know.
    
    The following is from Design News 10-21-85 "Clarifying Battery
    Selection"
    
    "Nickel-cadmium has been the traditional choice for consumer appliance
    batteries, given its long (500) cycle life and its availability
    in small sizes."
    "...the nickel-cadmium battery's life is estimated at 5 to 7 years
    to 80% of rated capacity..."
    "The nickel-cadmium battery carries the disadvantage of memory effects.
    In addition, it must be kept on charge continuously. If left on
    open circuit, the nickel-cadmium battery will lose 1% of its capacity
    daily."
    "From a self-discharge standpoint, the nickel-cadmium battery can
    be recovered after 3 to 5 years in storage."
    
    From a data/characteristic table:
    
    Float Service Life: 4-8 years, memory effect may give problems
    Float Charging: Constant current only, C/30 to C/10 at room temp.
    Cyclic Service Life: 500 or more cycles with a well defined schedule;
    			 normal consumer applications cycle life is
    			 about 300 cycles.
    Cyclic Charging: constant current only, C/10.  Fast-charge capability
    		     with charger that senses temperature and/or voltage
    Storage Life: (interval between recharges at room temp.) 2-3 months.
    		  can be stored in discharge state.
    Discharge Characteristics: Excellent at rates up to 10C; Good low
    		temp performance; poor high temp performance
    Special Considerations: Leaving load on battery can cause cell reversal
    			    problems.
    
    * C/x rate: current necessary to discharge or charge a cell of given
      rated capacity (C) in x hours if the cell maintained the same
      rated capacity at all discharge rates.
    -----------------------------------------------------------------------
	Well, there it is...  for what it's worth.  Of course, the usual
    disclaimer: I in no way assume responsibility for, nor am I associated
    with Gates in any way, or even understand entirely what I have written
    ,or what a disclaimer is good for other than the waste of disk space!
    
    Happy RCing!
    
    Eric
    
================================================================================
Note 53.8                       NiCad Batteries                          8 of 18
FROST::RICHARDSON "Eric Richardson"                  13 lines  20-FEB-1986 15:35
                             -< clarification.... >-
--------------------------------------------------------------------------------

    In re-reading the what I had previously just written, I saw something
    that might cause a bit of confusion.....  Where it states the nicad
    has to be kept on charge constantly when not in use, they are refering
    to batteries used in things like cordless phones, black & decker
    dust-busters, etc.  Those sorts of items are constantly trickle
    charged so when you want them they are ready.  Left sitting unplugged,
    they would be useless after a short time (unless you wanted to charge
    them the night before like RC equipment....)  Needless to say, this
    non-cycle, constant charge system takes its toll on nicads.  Now
    you know why your Dust-Buster won't last through cleaning the front seat
    of your car!
    
    Eric
================================================================================
Note 53.9                       NiCad Batteries                          9 of 18
SCOTCH::KENNEDY "Mat Kennedy"                        26 lines   4-MAR-1986 10:22
                        -< Report on RAM Simple Cycler >-
--------------------------------------------------------------------------------

I finally got the time to set-up and use the RAM Simple Cycler mentioned
in .6. I was a little suprised when I opened the box when I received
it. It is simply a 3" x 3" plastic case with a tiny circuit board glued
to the inside. There are four wires coming from the circuit board. You
put connectors for radio on one and reciever pack on the other. Two
for the 9.6volt radio connector and two for the 4.8volt receiver pack.
It looks as if it cost a $1.50 to make but I figured if it worked it was
worth the $16.00 I payed for it. 

I soldered the connectors (not supplied) on and proceeded to plug it into
and discharge the radio, then the receiver pack. You can only discharge
them one at a time. When it reaches the appropriate discharge level it
sounds an alarm. You then connect to the charger that was supplied with the
radio system. 

It worked fine. There is a chart that comes with it for determining
the amount of charge your packs are accepting. It is based on the
time to discharge the fully charged pack. 

For $16.00 it seems to be worth the small investment. Although it is
an entirely manual process to cycle packs this way, it does get the
job done.

-Mat


================================================================================
Note 53.10                      NiCad Batteries                         10 of 18
MDADMN::EATON "Dan Eaton"                             7 lines   5-MAR-1986 11:13
                       -< More on the RAM Simple Cycler >-
--------------------------------------------------------------------------------

re: 53.9 
    Gee, this came just in time. I just recieved a flyer from Tower
    Hobbies yesterday. They have a sale on the RAM Simple Cycler and
    I was going to put a note in asking if anybody had any experiance
    with the beasty. Thanks for the info.
    
    Dan Eaton
================================================================================
Note 53.11                      NiCad Batteries                         11 of 18
PICA::FRIEDRICHS                                      4 lines   5-MAR-1986 23:37
--------------------------------------------------------------------------------

    I use one of them too....  It does the trick.
    
    Cheers,
    jeff
================================================================================
Note 53.12                      NiCad Batteries                         12 of 18
SHIRE::CAUBERT                                       17 lines  25-SEP-1986 04:39
                               -< memory effet >-
--------------------------------------------------------------------------------

    does anyone known what produces the "memory" effet ??
    
    What occurs inside the cell with the chemistry during
    
    the charge and during the discharge ?
    
    Is there any way to avoid this "memory " effet ??
    
    like for example charge with a certain percentage of
    
    reverse current (say 10 to 20 % ? Would this method
    
    prevent the "memory effet "
    
    More info wanted pse.
    
    
================================================================================
Note 53.13                      NiCad Batteries                         13 of 18
CRVAX1::KAPLOW "There is no 'N' in TURNKEY"          13 lines  25-SEP-1986 18:52
                             -< Just don't do it! >-
--------------------------------------------------------------------------------

        What produces it, and what is the chemistry? Beats me. Probably
        something like some of the material getting into a permanently
        oxidized or reduced state in the cell. 
        
        How to avoid it? Don't do it :-) The reason for all of these notes
        on this topic is to let folks like you know about the problem, so
        that you can avoid it. 
        
        Reverse charge the cell? Yup, that would prevent "memory"
        problems, but after you destroy the cell, and maybe even blow it
        up, I don't think that memory will be what you are worried about.
        *NEVER* reverse charge a nicad, nor should you discharge it so far
        that it undergoes polarity reversal. 
================================================================================
Note 53.14                      NiCad Batteries                         14 of 18
FROST::SOUTIERE                                       8 lines  26-SEP-1986 07:46
                            -< Still Confused!@$% >-
--------------------------------------------------------------------------------

    What if you don't have any type of discharging device.  After flying
    for about 20 minutes you go home and do what?  Leave the switch on
    so the batteries will run down or recharge them.  I'm still a little
    confused on how much charge they will hold if they are not completely
    discharged.  Also, how long should the charge be.  The manual that
    came with the set says 15 hours if the batteries are not used for
    quite awhile.  I really don't want to destroy my battery pack if I
    can help it.
================================================================================
Note 53.15                      NiCad Batteries                         15 of 18
PYONS::TAVARES "Stay low and keep moving..."         45 lines  26-SEP-1986 10:50
                            -< Discharging Nicads >-
--------------------------------------------------------------------------------

    I've hesitated to jump into this one because I don't know the details
    of nicad chemistry, and I charge my batteries on home-brew equipment.
    But, maybe I can help a little.  Nicads, as you probably know, have
    a discharge curve that tends to hold the cell voltage for a long
    while, then fall off rapidly.  This is why an expanded scale voltmeter
    is used to check the pack; a voltage drop of .2V/cell is considered
    grounds for recharge.  For your receiver pack, this means that you
    recharge at about 4V, load voltage.  
    
    What I do when I'm in doubt about the pack, as when I've been out
    for a short time and I want to be sure the batteries are good, is
    to put a resistor across the cells to drop them.  For the receiver
    pack, put a 50 ohm resistor across the battery terminals.  This
    will put about a 100 milliamp load on the battery.  Then check the
    pack; it should read more than 4V.  If I want to recharge, I would
    simply leave the resistor on for a while until the voltage drops.
    A 25 ohm resistor will, naturally, discharge the pack faster; at
    200 mils.  
    
    For charging, that's where the commercial stuff is nice.  These
    goodies charge at what the manufacturers call C/10 rate; that is,
    the rate is equal to 1/10 of the cell's capacity.  For a 500 mil
    pack, this is 50 mils.  The C/10 rate is designed to give a "full"
    (actually around 80 to 90% of capacity) charge overnite; that's
    what the magic 15 hour is about.  
    
    Whenever the batteries have dropped to -.2V/cell, you can safely
    charge at the C/10 rate.  Now, if you want to charge at higher rates,
    say at C/2 (electric flyers will charge at 3C to 4C!), you have
    to be much more careful, and use batteries designed for fast charging.
    Such batteries are clearly marked on their case; if they don't say
    fast charge, don't do it.
    
    Also, if my batteries are sitting for more than 10 days, I will
    discharge and recharge.  
    
    As to memory effect, this is caused by recharging a battery that
    has partially discharged; that is, one that say, when you put the
    load on, only drops to 4.4V or so.  It is caused by the chemistry
    of the battery; again I don't know.  As I understand it, current
    nicads are very resistant to the memory effect;  I don't care, I
    still discharge and recharge.  Same with other precautions relating
    to the variation in voltage between cells due to different internal
    resistances; current cells render such precautions obsolete; I still
    take them.  
================================================================================
Note 53.16                      NiCad Batteries                         16 of 18
SPKALI::THOMAS                                        7 lines  26-SEP-1986 12:19
                              -< MR,   PLEASE?? >-
--------------------------------------------------------------------------------

    
    
    		Hey, maybe one of you handy dadny electrical
    people could design a discharge/change test box to help
    us non electrical folks.  Using DEC P/N's would help.
    
    					Tom
================================================================================
Note 53.17                      NiCad Batteries                         17 of 18
PYONS::TAVARES "Stay low and keep moving..."         15 lines  26-SEP-1986 12:28
                                -< Topping Off >-
--------------------------------------------------------------------------------

    Forgot to add some stuff about "topping off".  As I said in .15,
    the C/10 rate at 15 hours (actually, its 16 hours) only puts in
    80 to 90% of full charge.  This is because of internal losses in
    the cells.  The cells can be left on longer, actually, at the C/10
    rate, most current cells can be left on indefinitely.  But nicads
    do not top off easily; another characteristic, I don't know why,
    but I think it has to do with internal heat and diminishing returns.
    
    An accepted way, and a safe one, is to reduce the charge to C/100
    and continue for awhile longer.  What I do, say for the 500 mA pack,
    is to put the pack on in the evening and charge at 50 mils for 16
    hours, then reduce the charge to 5 mils and let it go for the day.
    This is about all you can do to fill the battery; sort of like the
    old story about topping off the camel.
    
================================================================================
Note 53.18                      NiCad Batteries                         18 of 18
FROST::RICHARDSON "Eric Richardson"                  18 lines  26-SEP-1986 18:10
                    -< This mind left intentionally blank >-
--------------------------------------------------------------------------------

    Seems that I've read something to the effect preventing memory
    (or at least helping) by deep-cycling the cells after about 10
    incomplete charge cycles.  This "once-in-awhile" cycling keeps
    the chemistry in good shape.  
    
    Regarding the DEC-part goodies, I have built a little unit that
    discharges my flight pack at a preset rate, then displays an
    LED when just at the knee voltage. (sort of my version of a 
    RAM Simple Cycler, only not as versitile.)  I found that unless
    you like to scrounge parts and tinker, for your time and effort
    it's easier to just buy something like a Simple Cycler.  If 
    anyone wants to see the schematic, just say the word.  I'm in
    the process of doing the same for my transmitter pack, so I don't
    have the exacts of that yet.
    
    Eric
    
    
================================================================================
Note 196.0                          Nicads                            No replies
EARTH::SCANTLEN                                      16 lines  25-SEP-1986 12:34
--------------------------------------------------------------------------------


    The use of a cycling device such as ACE R/C's DIGIPACE once a month
    will help prevent/correct any memory effect, which is actually a
    loss of capacity.  The cyclers discharge the pack so each cell voltage
    is typically 1.1 volts, and then recharge at the slow overnight
    rate.  Don't just leave on the Xmitter, or RCVer, as you may discharge
    to far...
    
    In the case of 'leaving on the xmitter' till the batteries are 'dead',
    some nicads will recover by as you say, a reverse charge.  This
    really is not recommended and could cause the cell to destroy itself.
    In any event, the life of the cell will be much shorter than with
    proper care and feeding...
    
    			-Mike
    

================================================================================
Note 78.0                      Belly-up Battery                       11 replies
NRCP2::GARCEAU                                        8 lines  10-FEB-1986 10:27
--------------------------------------------------------------------------------

I have been flying R/C for about 3 years not off & on. I left my flight box
m-cycle battery in the garage this winter and this w/e I took it out to try
to charge it overnight - does'nt seem too healthy. Will it live again? Will
a change of electrolyte help?

	Brian Garceau


================================================================================
Note 78.1                      Belly-up Battery                          1 of 11
FROST::RICHARDSON                                    28 lines  10-FEB-1986 17:45
--------------------------------------------------------------------------------

Hi Brian,

How long has it been since you used/recharged the battery?  Did the electro-
lyte freeze?  Define "doesn't seem too healthy."

The best short term advice is to check the cells one by one with a battery
hydrometer.  This will tell you the condition of the electrolyte to some
extent, and should point out a "bad" cell, if there is one.  If none of the
cells come out way low on the hydometer, but the hydrometer also doesn't
respond much to any cell, then maybe new electrolyte might help.  I must
admit though.... I've never seen anyone swap electrolyte in a battery.  
Usually the water is low, or a cell(s) are shorted.  

Someone may want to correct me, but it seems lead-acid batteries have a few
of the properties of nicads and other types: In this case, lack of use,
where the battery might discharge and sit for a long period of time. Infrequent
use is tough on batteries.  Lead-acid batteries also accumulate sediment
in the bottom of the cells.  After a while, the sediment shorts out the cell.
(which is why you shouldn't invert a lead-acid battery, not to mention avoiding
acid showers...)

Since I'm sure a lot of us modelers use lead-acids, I hope we can get some
good info here.

Regards,

Eric

================================================================================
Note 78.2                      Belly-up Battery                          2 of 11
NRCP2::GARCEAU                                        8 lines  11-FEB-1986 06:59
--------------------------------------------------------------------------------

There is a good possibility that that electrolyte would have frozen, if that
stuff ever freezes! It has been out in the (unheated) garage all winter and
has not been used for about 9 months. I will check the cells individually
and look for deposits on the lower portions of the plates. - Thanks, very
helpful!
	Brian


================================================================================
Note 78.3                      Belly-up Battery                          3 of 11
ANGORA::BUSHEE                                        4 lines  11-FEB-1986 09:34
--------------------------------------------------------------------------------

	Also beware of storing lead-acid battries directly on a cement
	floor as this will draw any charge out of it and kill it.

	George
================================================================================
Note 78.4                      Belly-up Battery                          4 of 11
CACHE::BRETSCHNEIDE                                  12 lines  11-FEB-1986 12:03
--------------------------------------------------------------------------------

If the charge is low, a lead-acid battery can and will freeze.  I had it
happen to the one in our Fiesta a couple of years ago.  We took the battery
into the house and thawed it out, put it on the charger and it lived a while
longer.  It seems to me that we had to replace it about a year later.  The
total life on the battery was about 4-1/2 years old.  Since it was the original
equipment battery from 1980, I guess it might have been ready to go.  When
it was frozen, it would peg the charger (6 amp machine) on the high end until
the thermal overload would cut out.  Then the cutout would cool down and
restart the charger causing the cycle to repeat again.  Hope this has been
of some help.

Bruce Bretschneider
================================================================================
Note 78.5                      Belly-up Battery                          5 of 11
NRCP2::GARCEAU                                        7 lines  12-FEB-1986 07:04
--------------------------------------------------------------------------------

I checked the battery cells with a hydrometer. All cells registered zip,
in other words, all the little balls sank! I bought a new battery at Tom's
on the way home last night also so I am not longer bound to this battery.
If I read the advice in .1 properly the original battery is gonzo, correct?
	Brian


================================================================================
Note 78.6                      Belly-up Battery                          6 of 11
FROST::RICHARDSON                                    31 lines  12-FEB-1986 12:16
--------------------------------------------------------------------------------

I would say 'yes', the battery is a hurting ticket and should be given
a decent burial.  If you've tried charging it and the electrolyte couldn't
even begin to float the hydrometer, then chances are it isn't worth playing
with.  Since you've already gone out and bought a new one, that makes it
unanimous.

As for the effects of freezing on a battery, I'm not sure what it does to
the electrolyte exactly, but I'm pretty sure it doesn't help it.  A big 
problem with frozen batteries is it might rupture the casing, and possibly
damage the plates to boot.

As for a battery lasting 4 1/2 years, especially an 'original equipment'
battery,  I'd say that's pretty good. My Delco auto battery lasted almost
five years, but it didn't like winters in the least.  My original motorcycle
battery (for my motorcycle) lasted about 3 years, and that was taking pretty
good care of it.

Regarding taking care of your new battery, if it's in storage, keep it warm
and charge it about once a month.  Unlike nicads, I don't think lead-acids
need to be deep-cycled.... In fact, only marine and RV batteries are usually
intended to be deep-cycled.  If you want your lead-acid to be happy: keep
it charged.

Re: 3  pretaining to not storing a battery on a concrete floor,  I've never
	heard that one, but at this point I wouldn't doubt anything.  I'll
	have to check into that one.  Where did you find that advice?

Happy RCing,

Eric

================================================================================
Note 78.7                      Belly-up Battery                          7 of 11
ANGORA::BUSHEE                                        7 lines  12-FEB-1986 14:24
--------------------------------------------------------------------------------

	RE: .6

	I've had this told to me several times by different mechanics, plus
	I also read in an old popular mechanics that the damp cement floor
	can cause damage.  Don't ask me why, I havn't the foggest.... :^}

	George_B.
================================================================================
Note 78.8                      Belly-up Battery                          8 of 11
FROST::RICHARDSON                                    13 lines  12-FEB-1986 16:39
--------------------------------------------------------------------------------

OK George, you're off the hook... :^)

I just called up my normal mechanic (my dad) and asked him.  He confirms
that it isn't a good idea to store them for long periods on a concrete
floor, and battery and charger literature often states not to charge
the battery when it's on the floor either.  As for why; probably something
to do with the chemical/caustic action of concrete. (same reason tires
will flat-spot if left sitting on concrete too long?)  I'm curious, so
I'll look into it further.  In the mean time, all my batteries are gonna
go somewhere else.

Eric

================================================================================
Note 78.9                      Belly-up Battery                          9 of 11
CACHE::BRETSCHNEIDE                                   8 lines  13-FEB-1986 10:25
--------------------------------------------------------------------------------

I have left batteries on the garage floor and had no problems as long as
I put something under them, e.g., newspapers or plywood.  

It's my understanding that the cause of 'flat-spotting' of tires is the use
of nylon cords in the tire.  If you mean that the rubber gets eaten away,
I've never heard that one before.

BB
================================================================================
Note 78.10                     Belly-up Battery                         10 of 11
PYRITE::OWEN                                         15 lines  13-FEB-1986 15:33
--------------------------------------------------------------------------------

Can I make a guess here?  And it is just a guess.

I doubt that the flat spotting of tires and the death of your battery are
related.  In the tire, my guess is that the rubber compresses over time at
the surface where the rubber meets the road.  Left long enough it looses some
elasticity.  In the battery, my guess is that the temperature differential
between the concrete floor (the bottom of the battery) and the surrounding
air (the rest of the battery) is the culprit.

This would account for the fact that raising the battery just a bit to allow
for air circulation under the battery is a solution to the problem.

I hope I haven't just put my foot in my mouth  :-)

Chuck
================================================================================
Note 78.11                     Belly-up Battery                         11 of 11
CRVAX1::KAPLOW                                       23 lines  14-FEB-1986 16:31
--------------------------------------------------------------------------------

re .6

I too once turned a car battery into a caustic ice cube. It was the original
battery, four years old, and in not too good shape to start with. One of those
-25 days hit Chicago with a wind chill down to -80. Well, I was out anyway
(taking my soon to be wife to work), and the fuel line froze on the way. It
didn't tale long with that wind for the battery to become terminal (sorry about
that). After that, there wasn't much to do but buy a new one a week later.
Moral: batteries don't like cold. Nicads will take more than any of the other
dry cells, but they too quit in sub-zero temperatures. I don't really know about
lithium cells, but they aren't common enough to worry about. 

The best way to store a lead acid cell (including gell cells) is to keep it on
trickle charge, with a charge rate of something like C/100. They last longer if
you do this than if you just leave them around in a random state of charge, and
they are always fresh and ready to go when you need them. I've made trickle
chargers out of old calcualtor transformers, a couple diodes, and the right
connectors. An ACE vari-charger also works fine for this. You are also correct
that there is no need to cycle them down before charging them back up. 

Nicads on the other hand, are best stored in their discharged state, and charged
up to full power as needed. Trickle charging nicads is bad news for their
long-term health. 

    
    	This is my first year in R/C. I also opted for the tower hobbies
    flight line tote box and thier distribution panel. I however bought
    the Calcuim Cadmium closed rechargeable battery since I was very
    worried about spilage in the box. I modified the box to allow an
    external parallel connection to the battery via a side of the box
    500ma Radio Shack battery charger panel mount connector. In this
    way I simply place my box within three feet of a 120v outlet and
    plug it in as if it were a calculator for an overnight charge.
    	Seems to work just fine, but I will have to see how things 
    work out as the season progresses.
    	I know from experience in the service what can happen to the
    hydrogen gas given off by a charging lead acid type battery in 
    a confined space, as well as coming into contact with the electro-
    lyte. I intend to stay well away from them at all cost.
    
    				Michael Gallant
    

    
    To answer the original nicad question, I would not recommend the
    use of your batteries in a battery holder for two reasons.  Firstly,
    the condition of the batteries could be suspect. Secondly, and more
    importantly, you have a number of contacts which will be highly
    susceptable to vibration.  I would not use a pack that did not have
    welded or soldered connections. Why risk all that time and money
    to save $10 or $20 in a critical component?

        re: .11
        
        I too prefer gell cells whenever possible. Their chemistry, and
        thus their care and feeding is the same as the lead acid The
        obvious exception is that they are sealed, so you don't have to
        worry about acid spills, venting, inverting, etc. 
        
        The only disadvantage to gells is their size, so I still use
        nicads in small applications, like RX packs. I have 6v and 8v gell
        cell packs that work fine in my RC car, and run for twice as long
        as any nicad pack I've seen. The extra weight of the gell cell
        helps traction on poor surfaces as well. 

   OK, who wants to recommend some brand names and locations to buy 
them?  I am considering buying the following:

     Description		Price		Vendor
------------------------------- --------     ----------------
 SANYO TX-PACK 9.6V - 500MAH     $14.22     J.C. DEVELOPMENT CO.
 SANYO 550 mA Receiver NiCd      $10.99     TOWER HOBBIES

 RAM SIMPLE CYCLER               $16.99     TOWER HOBBIES

  I am also going to need a charger, any recommendations on these? 
I don't want to spend and arm and a leg.  I don't fly any electric
powered planes, so I don't need to fast charge at the field.


   Jim C

All reports of Sanyo that I've read say that their batteries are top
notch.  Also, based on some recent experience with other mail order
houses, I heartily recommend Tower.  I'm beginning to think they're
the only professionals in the business.

    On flight pack batteries...the pre-assembled nicad packs are the
    way to go.  I've run RC Cars with the battery holder scheme, and
    it is subject to dislodging a cell.  This could happen on a hard
    landing with an airplane, and then completely dislodge in the air
    with obvious 'I ain't got it' syndrome.  
    
    All nicads aren't created equal, it pays to buy the best you can
    get, and in home use, I don't even recommend the Radio Shack.  Perhaps
    their new Hi-Capacity cells are better, but I've never tried.  The
    Sanyo's are good as indicated in previous reply.  You can buy the
    pre-assembled packs minus the connector, and install the type to
    fit your radio system.  
    
    I've dealt with Tower since 1971 with positive results.  This was
    about the time they first opened up.

 re .-1


>    On flight pack batteries...the pre-assembled nicad packs are the
>    way to go.  I've run RC Cars with the battery holder scheme, and
>    it is subject to dislodging a cell.  This could happen on a hard
>    landing with an airplane, and then completely dislodge in the air
>    with obvious 'I ain't got it' syndrome.  
 


		Wind some insulating/sticky tape round the
	middle of the holder.This keeps them all in nice and tight.


bob

    Maybe someone can help me. After reading this notes file, I'm still
    confused about discharging of battery packs. An article I read in
    a magazine states that it's best to always discharge a pack through
    a 30ish ohm resistor. It goes on to say that the resistor should
    be left connected while the pack is not in use. 
    Doesn't this discharge the pack too far and possibly result in cell 
    reversal?
    
    Thanks,
    	
    	Ron

        Do NOT leave the resistor on after discharging the pack! You are
        correct that this will drain the pack too far, and almost
        guarantee reversal or other damage to the cells. For best nicad
        life you should only discharge to about 1v per cell. That is about
        the location of the "knee" in the discharge curve, at which point
        the voltage will begin to fall rapidly. For longest nicad life,
        the pack can be left in this discharged state for several months,
        and charged just before you are ready to use it. 

        30 ohms sounds a bit high for my tastes. That would be about
        a 170ma drain on a 5v pack, 340ma on a 10v pack. I prefer to
        discharge at the same c/10 rate that I charge at. That would
        be a 100 ohm resistor for a 5v 500mah flight pack and 200 ohms
        for a 10v 500mah pack. Use Ohms law (I=E/R or R=E/I) to calculate
        these values.
        
        Either way, you also need to note the power drawn (P=I*I*R) to
        determine the wattage for the resistor. Your 30 ohm resistor would
        need to be at least 1 watt (4 watts for 10v). 1/4 watt would be
        marginal for the 100 ohm example, and 1/2 watt for the 200 ohm. I
        have some large 500 ohm wire wound resistors that I use for this
        purpose. Several in parallel give me lower values as needed. 
        
        For larger packs (RC cars, etc.) a properly chosen car light bulb
        gives both a proper discharge rate, and a visual indication of the
        current discharge state.
        
        A battery cycler does all of this for you. It might be worth the
        bucks to avoid all of the hastle. 

    Re: .19
    
    I discharge my battery pack with a 20ohm, 5W, 1% and watch it with
    a meter while it discharges.  I take readings every 10 minutes (while
    watching TV or something...) and wait until I see the knee in the
    curve (about 4.2 - 4.3V).  I then calculate the mAH based on the
    10 minute intervals and make sure I still have ~450mAH left in the
    pack.  I then recharge overnight (yes, at the C/10 rate) and go
    flying!
    
    I really like to see the graph (DECCalc works great) to make sure
    I'm not dropping a cell early.  If you've got a PC of sorts at home
    and can rig up an A/D and a relay, you could automate this thing.
    
    Enjoy.

I found a great reference in DEC's Maynard Library on batteries.  It has 
chapters on all types of battery technologies (a few hundred pages total).

	HANDBOOK of Batteries and Fuel Cells
	McGraw-Hill Book Company, 1984
	ISBN: TK2901.H36

For those of you that want more technical information on batteries I suggest
you obtain this reference.  A typical chapter has information for one battery
technology (for example, I read the chapter on sealed Ni-Cads).  The chapter
outline is listed below.

18  Sealed Nickel-Cadmium Batteries
	18.1  General Characteristics
	18.2  Chemistry
	18.3  Cell Construction
		18.3.1  Cylindrical Cells
		18.3.2  Button Cells
	18.4  Performance Characteristics
		18.4.1  General Characteristics
		18.4.2  Discharge Characteristics
		18.4.3  Effect of Temperature
		18.4.4  Internal Impedance
		18.4.5  Service Life
		18.4.6  Cell Reversal
		18.4.7  Shelf and Cycle Life
		18.4.8  Life Expectancy and Cell Failure
	18.5  Charging Characteristics
		18.5.1  General Considerations
		18.5.2  Pressure, Temperature, and Voltage Relationships
	18.6  Cell Sizes and Manufacturers

As you can see there is plenty of information.  The Ni-Cad chapter is 20 pages
in length.  The text is well written, not 'too' technical, and includes plenty
of diagrams and graphs. 

    RE: .20,21,22                       
    
    Thanks for the info on batteries and discharging! I definitely have
    to develop a systematic method of doing this. It has to be simple
    enough so that my 10 year old can manage the proceedure on his own
    when necessary. Think I'll invest in a cycler someday. In the meantime
    I'll use a resistor as suggested. I have also heard that it's not
    good to always fast charge. An occasional tricle charge (one for
    every 5 fast charges is one rule of thumb I heard) is necessary
    to maintain cell equalization. With the number of variables involved
    (several batteries, several users, fast charge, tricle charge,
    discharge...etc) I think I'll have to start a log book. Thanks again
    for the info guys.
    
    			- Ron 

    A quick comment on the discharge resistor value.... A RAM Simple
    Cycler discharges the 4.8V pack through 22 ohms and the 9.6V
    pack through 44 ohms.
    
    For what that's worth
    
    Eric

That's a 218 mil load on the batteries.  For my 2 cents, I think
that this load is OK to test the receiver pack, but I like to see
something closer to 250 mils for the transmitter pack.  I test my
receiver and transmitter batteries at around 280 mils.  The
average transmitter will draw at least that.

As I understand it, some cyclers define a good battery as one
that can be discharged at 250 mils for 100 minutes; for a
receiver battery, this means going from a full charge to 4.4
volts in 100 minutes; for a transmitter battery its from a full
charge to 9.0 volts.

    I am currently flying a Leisure Wasp with a Leisure LT50 BB motor
    and 6 cell pack.  I have been using the following system for
    recharging.  Use an Astro 6/7 cell 12V fast charger, set the timer
    for 15 minutes.   Place DVM across battery and after first 15 minutes
    continue charging until I see the pack voltage just start to drop.
     Is this correct?  Am I over charging?  Will I shorten the pack
    life?  The packs never get hot while charging.
    
    BTW - This Leisure Wasp is one fun plane.  It's capable of lots of
    aerobatics and I get about 6 min of flight time per charge.

You are shutting off the charging at the theoretical optimum
point.  It takes a lot of fancy circuitry in the chargers to do
that.  Of course, your risk is that one of these days you're
going to miss that dropoff, and with the fast charge rate you're
using, you'll nuke a pack.  Why do you need such a fast rate?
Even though the manufacturers rate the batteries for the fast
charge, I'm cautious because the inside of the batteries is
partially liquid, and the fast rate builds up heat that must
evaporate some of that liquid with every charge.  Just shortens
battery life.

         I use the fast charge rate because I have 2 battery packs and
    like to fly the plane as many times as I can in one session.  I
    understand some chargers have a thermistor that you attach to the
    battery pack that shuts everything down when the pack gets warm.
     Wouldn't this occur too late?  I think I will modify my procedure
    and shut down when the battery voltage levels out just prior to
    the reversal.  It is very evident with the DVM when this happens.

While some chargers do use the temperature sensing method to
determine full charge, I do agree that this stresses the
batteries too much.  

  Not knowing much about batteries, I figured I'd better ask some 
questions before I trash my electric motor.

  What is the actual meaning of Mah versus AH?  Is it just the time
it takes to discharge or what?


  Jim

    Jim,
    
    The way I understand it...maH and AH are measurements of the discharge
    capacity of the cell.  For example:
    
    A cell rated at 1200 maH (same as 1.2 AH) when discharged would
    yield 1200 milliamps ( or 1.2 amps) for 1 continuous hour.
    
    Or say 600 milliamps for 2 hours...  2400 ma for 30 min. and so
    on.
    
    Also, maH is Milliamp hours and AH is Amp Hours.
    
    hope this helps,
    
    Chris
    

  So Chris, your saying that using a 6 volt 4.5 AH battery won't fry
my motor if it calls for a 6 volt 1200Mah battery. Right?
  The reason for my questions is I am trying to figure out what I need
to get for my boat.  I don't want to have to change/recharge the batteries
every 5 mins.  
  The boat is 5 feet long so I have plenty of room for batteries.  I don't
want to be restricted to small packs either.


  Jim

    Jim,
    
    What Chris said regarding battery capacity is correct, as is yer'
    conclusion that a 1200mah battery versus a 4.5ah battery won't 
    damage yer' motor...as a matter of fact, 1200mah figures to 1.2ah
    so yer' actually talking about a smaller, not a larger capacity
    pack.                                        
    
    Lemme' see if I can clarify further for ya':  1-milliamp = 1/1000-amp,
    therefore 1000-milliamps = 1-amp.  In numbers more applicable to
    our useage, 500mah = .5ah which, as Chris explained, means this
    pack will deliver 500 milliamps for a period of 1-hour of continuous
    "on-time."  Think of it this way: say you need 6vdc to run yer'
    motor...the amp/milliamp-hour rating can be considered the fuel
    capacity - the higher the rating, the longer the battery will deliver
    the 6-volts.  Amp/milliamp-hour rating has no effect on the device
    being operated other than the length of time it will run on a single
    charge.                                   
    
    Adios,	Al
    

    Jim,
    
Remember Nicads are considered flat at 1.1v per cell. Consistently going below 
that will damage cell's permanently.

John.

    Does anyone play with Gates sealed lead-acid 'damp' CYCLON cells? 
    I've used them for everything from clock backups to marine radio
    UPSs to robots and a really bright flashlight (if you count a car
    headlight as a flashlight bulb...), and for my money they are the
    ideal rechargable battery.  You can charge them at 4C to 5C (say
    15 minutes from dead flat) and can easily get over 100 amps from
    the D cells.  Unfortunately for plane enthusiasts, the smallest
    size they make is the 'D' cell, but I would think they would work
    well in cars/boats/etc.  Radio Shack carries the 'Monoblock' 2.5
    AH 'D' and 5.0 AH 'X' 6 volt batteries as replacement packs for
    their portable cellular phone.
    
    Willie

    Willie,
    
    For use in radios, at least, the key is the discharge curve.  Pro-
    portional radio systems require a constant voltage and, thus far,
    ni-cad batteries provide the flattest discharge curve available
    at reasonable cost.  They'd probably be fine for running an electric
    motor or other device NOT associated with the radio itself.
    
    Adios,	Al

RE:

>    Think of it this way: say you need 6vdc to run yer'
>    motor...the amp/milliamp-hour rating can be considered the fuel
>    capacity - the higher the rating, the longer the battery will deliver
>    the 6-volts.      


  Thanks Al, that puts it in terms that even I can grasp!


  Jim

    The Gates lead-acid batteries are the ones used in the kid's motorized
    cars, 4x4 etc (the ones they can ride in).
    
    I picked up two 6v 9.5ah El-Power lead acid batteries like the ones
    above, new in the box, surplus for $8.00 each (with charger).  Make
    great flight box and starter power.  
    
    Available from most electronics surplussers for $10-20 each.
                        

  FYI - found this in the VNS this mornining:

                    Jim





                     Rechargeable Lithium Cell

       A new rechargeable lithium battery cell capable of about 2.4
       times the energy output of a high capacity nickel cadmium cell
       has been developed by Sony Energytec.  The ability to deliver
       higher energy in a cell of the same size is due in part to a
       higher operating voltage, 2.8 V compared with 1.2 V for NiCad. 
       At the  same time, weight has been reduced due to the low
       weight of lithium.  The subsidiary of Sony Corp. says that a
       manganese compound used as the anode provides excellent
       reversibility of the chemical reaction during charge and
       discharge.  An organic solvent electrolyte makes for a
       negligible self discharge current and shutdown of current flow
       at the end of a charge cycle.  Sony will introduce the first
       products based on the new  technology next year.  
       {Electronics Jan 7, 1988}

    Let's see, this looks like a good place to ask this...
    
    I am no longer confident in any of radio batteries.  Out of the
    3 systems that I have, I know that 1 Tx and 1 Rx batteries are 
    no good.  I admit to not caring for them properly.  I am planning
    on getting an LR Taylor battery cycler...
    
    The question is, what do I replace them with??  They are FUTABA
    systems.  Futaba wanted something like $27 to replace my flight
    pack on a system that I just sent back to them.  There are lots
    of packs on the markets, which is better and why??  How can I tell
    that Tx pack xyz is going to fit into my FG series radio??  Other
    comments on replacing radio batteries???
    
    Thanks,
    jeff
    

>    I am planning on getting an LR Taylor battery cycler...

* Great idea.  I haven't experienced an in-flight battery since starting to use
battery cyclers over 15-years ago.  Beyond that, regular and proper use of a cy-
cler will extend the life of yer' packs.  A good cycler is probably the "BEST"
investment an R/C modeler can make!
    
>    The question is, what do I replace them with??  

* Use only top-quality cells intended for R/C application...DO NOT use Radio 
Shack or other [even brand name] garden variety cells.  Tower sells Sanyo cells,
individually or in packs and these are one of T. H .E. best ni-cad cells avail-
able for R/C use.

>						.....They are FUTABA
>    systems.  Futaba wanted something like $27 to replace my flight
>    pack on a system that I just sent back to them.  There are lots
>    of packs on the markets, which is better and why??  How can I tell
>    that Tx pack xyz is going to fit into my FG series radio??  Other
>    comments on replacing radio batteries???

* Any 4.8vdc pack that will fit in the fuse may be substituted for the airborne
pack...only thing to decide here is what capacity you want; the normal airborne
pack is 500-550mah.  All transmitters have packs specifically designed to fit
whatever space has been provided within the case and the pack for Futaba "G" and
"J" series transmitters are especially unique.  They have a long, slim pack that
"appears" to have three rows of 3-cells each for a total of 9-cells.  This is an
illusion: one of the "cells" is, in reality, a dummy spacer and the pack is ac-
tually an 8-cell pack as is typical/normal.  To my knowledge, no after-market
manufacturer makes such a pre-assembled pack.  I purchase Sanyo cells and re-
build the pack myself, which is what I suggest you do, "IF" you are a competent
solderer.  Simply take the pack apart, noting how it's assembled, and reassemble
it using new cells.  One snag you'll run into is that the cells in the original
pack are spot-welded together so you'll have to substitute about a 1" length of
24AWG wire to connect the cells...rotating the cells will take up the slack and
provide a nearly flush connection like the factory pack had.  If all this is too
intimidating, yer' only alternative is to purchase the factory replacement pack 
for the transmitter.  The price isn't all that bad when you consider that ni-cad
cells retail for nearly $4.00 each making it a $32.00 pack.  I don't recall the 
price but I purchased a Futaba Tx pack from Tower Hobbies a few years back for
considerably less than Futaba's retail.  They [Tower] will be able to supply the
correct pack if you provide them with the full nomenclature, i.e. 7FGK-FM. The
pack connects to the logic PCB via a 2-pin connector so no soldering is required
to replace yer' own pack in this fashion.
    
Adios, 	Al    

	Ditto   Ditto  Ditto on the cycler.  I have an L.R. taylor
	and think its the greatest thing since sliced bread.  I fitted
	mine with deans 3 pin connectors and then made a bunch of
	deans to whatever adapters to fit various radio, battery
	and fuse plugs.

	I found myself believing all the literature from S.R. batteries
	about two years ago and bought a couple of thier flight packs.
	They look well made and in fact do exhibit the extra capacity
	for thier size.  Problem is.... they don't last much more than
	a year even with what I consider to be good care. (regular
	cycling, no overcharging, blah, blah, blah)  I am used to getting
	3-4 years out of factory stock Futaba packs and usually buy
	the stock replacements when I need them.

	Al,
	Thanks for the tips on the Sanyos, no fear of a solder iron in
	this corner.  I'm goin' to give them a try!!

	Ron

    Re: _.42, Ron,
    
    Uncanny!!  I too use the L.R. Taylor cycler and have set it up just
    as you have with the Dean's connectors so that I can connect the
    cycler to "any" of my packs.
    
    I had the same experience with the SR packs.  I bought a 700mah
    pack which was touted to [and did] deliver 900mah through a local
    distributor...the pack was installed in my MiG-3.  1-year and only
    about 20-flights later, the pack was junk!  Like you, I had done
    my usual care and feeding routine, keeping it charged and occasionally
    cycling during periods of non-use but it still went bad.  I went
    back to the distributor and said my "Buzzard-luck" had struck, that
    the pack was bad but, surely it was a fluke and I needed to order
    another one.  The distributor advised me NOT to order another SR
    as he'd had more than 25% of those he'd sold come back bad.  With
    that, I bought some 800mah Sanyo cells and assembled my own pack
    which has now been in the MiG for over 2 1/2 years with no problems
    and is still goins strong.  BTW, if you can find them, Panasonic
    cells are supposed to be on an equal par with Sanyo.  Sanyo's are
    so easy to obtain through Tower, however, that I'll just stick with
    them.
    
    Adios,	Al

    I just finished cycling my battery packs and I found a shorted cell
    in my Airtronics CS7P.  I have ordered two Sanyo receiver packs
    from Tower to build up a new transmitter pack.  You can quite often
    get 4 cell flight packs for about $8.00 from Tower when they are
    on sale.  I will use the other good cells for some non critical
    application like my daughter's walkman.
    
    By the way, never replace one cell in a nicad pack!  Since these
    packs are charged and discharged in series, it is important that
    the cells be closely matched in capacity.  Never put a new cell
    with a pack of used ones.  Replace the whole pack. 
    
    Charlie
    

    RE-1, I forgot to mention that I use a home built cycler that is
    hooked up to a microcomputer.  I not only get the discharge time,
    but I get a plot of battery voltage vs time during discharge.  I
    can also plot voltage during charge.  I can charge or discharge
    at a rate of up to .5 amps.
    
    CHarlie
    

    Please, tell us more about your cycler.  What kind of system is
    it hooked to??  How??  ect ect...
    
    jeff
    

    My homebrew cycler consists of two programable current sources for
    charging and discharging the transmitter and receiver batteries
    at up to 0.5 amps, and a voltage and current monitoring circuit
    for each battery.  The current sources are controlled by two D/A
    converters (8 bits about 2 ma per count).  The voltage and current
    monitors are muxed into an 8 bit A/D converter.  I scaled the voltage
    ranges such that I get maximum use of the 8 bit converter the same
    way an expanded scale voltmeter works.  The receiver voltage monitor
    has a range from 4.0 to 6.0 volts or about 8 mv per count.  The
    transmitter monitor has a range of 8.0 to 12.0 volts or about 16
    mv per count.  The current monitors both have a range of +/- .5
    amps full scale for about 4 ma per count.  I also have several digital
    control bits to turn the current sources on and off and to select
    discharge or charge mode.  I have three bits to select the analog
    mux channel for the A/D.  This whole mess is currently interfaced
    to a Radio Shack TRS-80 Model I that was gathering dust.  I also
    have an interface design for an IBM PC.  Any micro that allows a
    parallel interface could be used.  The control program is written
    in BASIC and the data is sampled at about one scan per second for
    display.  Every 5 minutes a sample is stored on disk for later
    plotting.  I know that this is overkill, but I did it with available
    parts and familiar technology.  It took me about a week to build
    this.  I have a notebook full of voltage discharge vs time plots
    for all of my batteries.  I don't use the charge capabilities very
    often, since it is easier to just plug in my charger that comes
    with the radio.  
    
    Charlie
    

    Charlie,
    
    The cycler sounds great! The TSR 80 is based on a 6809E processor
    right? I have a Dragon 32 (made in Wales!) also based on the 6809E. If
    I understand correctly, much S/W and H/W is interchangeable between the
    two (wasn't there a long court case about copyright or something?). If
    I grovelled very deeply, could you pass on some more details about the
    cycler (like circuit diagram, chips etc)? I've been considering for
    some time adding an I/O interface of the type describe and this
    application sounds good. 
    
    Any/all information gratefully received.
    
    Keith.

    The TRS-80 is based on the Zilog 8-80 8-bit processor which is quite
    different than the 6809.  The Z-80 was an enhanced version of the
    Intel 8080, which was one of the first useful microprocessors back
    in the early 70's.  The main difference interface wise is the I/O
    scheme.  The Z-80 and all of the other popular Intel Processors
    use separate instructions and addresses for I/O where as the Motorola
    processors like the 6809 use Memory Mapped I/O.  My design could
    be easily modified to work with a 6809 provided you know how to
    decode memory addresses and read and write to memory.  You need
    some available memory address space. (I decoded 8 addresses but
    only used 5)  My schematics are not really that clean yet since
    I tend to be lazy in that respect, but if you give me your mail
    stop, I will xerox what I have and mail them to you.  I will also
    answer additional questions if you decide to build something similar.
    I can help you with device part numbers, but I don't have any spare
    chips.  The only tough ones will be the A/D, D/A and the Power Op-Amp
    chips, and you could substitute other more available ones without
    much difficulty.  I used what I had in my junk/samples box.
    
    Software wise, if you have a decent version of BASIC, you will have
    an easy programming job.  I am still upgrading my program to make
    it more useful, but it is still fairly simple.  I may add some more
    nifty display features and some initial voltage checking to make
    sure the batteries are not connected in reverse.  I may also add
    a channel that is not only useful for 4 and 8 cell packs although
    that is all I use at the present time.
    
    Charlie
    

    
    One of the cells in my Airtronics transmitter battery pack shorted
    over the winter.  I'm glad I checked because I wouldn't have noticed
    otherwise (needle still was in the safe region).  I was able to clear
    out the short by charging a 10,000uF capacitor to 10 volts and zapping
    the shorted cell with it.  I will use this battery pack on the ground
    and put a new pack in the transmitter.
    
    Bottom line is - CHECK THEM BATTERIES, and do it with a voltmeter, not
    just the transmitter meter.  I did cycle them a couple times over
    the winter but I don't know when the short happened.  The battery
    voltage should be at least 9.6 volts with a 250ma or so load if all
    8 cells are ok.
    
    Other info - the transmitter is a CS7P-AM, the batteries are Sanyo
    500mAH, and the system is 3-4 years old.  Charlie had the same thing
    happen to his transmitter pack not too long ago (same transmitter
    and age).  The CS7P  meter doesn't measure battery voltage,
    it measures RF output, so it's easy to get a safe reading without
    one cell.  I haven't checked the receiver battery yet but will before
    I fly.  I may have just saved my trusty little Super Sportster from a
    horrible death!

    Bill

        Re: .35
        
        I've used both 6v and 8v Gates gell-cells to power an RC car. The
        D size (2.5 Ah) lasts over twice what the usual 1200 mah packs do.
        They are somewhat bigger, so they might not fit all cars, but I'd
        use them over NiCads any day. There is also an X size, at 5.0 Ah,
        it is too big for car use, but might be fine for boats, or ground
        support gear. I once used a 6V 8Ah big gell for a while, but it
        caused two problems, both due to the extra weight. First, it was
        way too heavy for the car suspension. Second, it raised the CG so
        far that the car wanted to flip over all the time! The 8v (4 d
        cell) pack also seems to slightly increase the tendency to flip,
        but that is more a result of the speed than weight. 
        
        Re: .50

        Absolutely! Check your NiCads after a winters storage. The NiCads
        in my TX finally died this winter, although zapping cured the two
        bad cells for now. The radio (Kraft 79 series) is old enough that
        it is due for re-nicading anyway; actually I'm surprised they
        lasted this long! The flight pack died long ago. Anyone know a
        good source for the 600 mah sub-c cells? If I had the space inside
        the TX, I'd convert it to gell cells as well. 

    re: .51
    
    	Are you sure you mean Gates "gell-cells"?  The ones you are
    describing sound an awful lot like the 'damp-cells' (starved
    electrolyte in a fiber insulator), which are much better than any
    old gelled-electrolyte batteries.
    
    Willie

    
    Just replaced the xmitter pack in my Airtronics.  Instead of buying
    the $28 replacement pack, I bought two 600 maH Sanyo receiver packs
    and soldered them together (Charlie Watt's brainstorm).  Saved me
    about $10 and fit in the transmitter perfectly.
    
    Bill

        Where did you get 600 maH Sanyo packs? How much? Were these the
        1/2C cells? That's just what I need for my Kraft; I went looking
        thru the catalogs I have, and found nothing but those awful GE
        cells; I refuse to buy them. 

    Re: .-1,
    
    I shared your opinion on GE cells 'til about a year and a half ago.
    I needed to re-battery my my G-series Futaba and a friend/fellow
    R/C'er was distributing and really bragging up a pack called "World's
    Best Battery Pack."  Since he praised them so highly (and the price
    was right), I installed a set of these batteries in the transmitter
    and airborne packs.
    
    18-months later, these cells continue to show better than 650mah
    when cycled on my L.R. Taylor cycler and they're only rated at
    550mah.  I've been tickled pink with the performance and only recently
    discovered that these are computer-matched "GE" cells.  Don't ask
    me the whys/whats/hows of computer-matchings...all I can say is
    that I'm _very_ satisfied with these packs and have had to re-think
    my opinion of GE nicad cells.    

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

    I may have said it before in this notesfile (or maybe it was in
    ELECTRO_HOBBY, can't recall). 
    
    GE sells (in the USA) 3 _different_ quality levels (maybe they're
    binned, I'm not sure) of NiCad battery...
    	
    	C)	"Consumer grade".  The black ones you can buy in department
    		stores.  Cheap- and crappy.  Some of them are assembled
    		in Mexico.  Avoid these except for your toddler's toys.
    
    	B)	"Better grade".  Sold to industrial OEMs.  Not a bad
    		cell; cost wholesale about what the consumer cells cost
    	  	retail.
    
    	A)	"Top grade".  Really Good Stuff.  Better than Sanyos.
    		Used only in critical applications- like portable medical
    		equipment.  Costs about $5 per D-size cell.  Can be
    		bought wholesale from GE, or in onesies and twosies
    		from H & R, Inc.  Philadelphia, PA.  (the full address
    		is somewhere in the ELECTRO-HOBBY notesfile).  Call
    		them on the phone; they'll send a catalog or read you
    		the A-H specs direct.  Have plastic money available-
    		H&R normally ships UPS Blue within 8 hours. 
    
    Testimonial:  I've bought multihundreds of dollars from H&R and
    I am very satisfied as to quality and speed of delivery.  
    
    Happy charging! 
                                                            
    	-Bill
    

    RE: .54
        
> Where did you get 600 maH Sanyo packs? How much? Were these the
> 1/2C cells? That's just what I need for my Kraft; I went looking
> thru the catalogs I have, and found nothing but those awful GE
> cells; I refuse to buy them. 
    
    Um, (dare I say it?)  Tower Hobbies.  $8.99 per receiver pack
    (phone special last month).  A bunch of us ordered the Sanyo
    packs thinking they were 550maH (as advertised) but the ones
    that came were 600.  The batteries in the pack are actually
    AA size.
    
    I just noticed they also sell 12 single Sanyo 600 maH AA batteries
    for $26.99  but I don't think they have the solder tabs.
    
    Bill

        Whoops, those aren't the ones I need then. My Kraft TX uses
        the 1/2C sized cells, which are also 600 MAh, but short and
        fat. I'll check out H&R, I'm always on the lookout for a good
        battery source.
        
        The catalog with the GE cells was from Indy. I've bought some of
        them in the past, and found that half of them didn't last for a
        year. Maybe that's why I don't like GE cells. 

        from the ELECTRO_HOBBY notes file:
        
        H&R Corp
        401 E Erie Ave.
        Philadelphia, PA 19134
        
        215-426-1708
        
        I just called and asked for a catalog. I will report what I find
        when I get it. 

    Sanyo doesn't sell a 1/2C cell (I have their product list here)
    they sell :

       	N-600SC	Standard charge 600MAH 2/3 Sub C size 26mm Height
    	N-900SC Standard charge 900MAH 3/4 Sub C size 34mm Height
       N-1200SC Standard charge 1200MAH    Sub C size 43mm Height
       
    and the same dimension cells in Fast Charge configurations, the
    suffix on the cell is SCR instead of SC.  All Sub C cells are 22mm
    or 23mm in diameter.
    

    PS. the Sanyo distributor in the New England area is ADCOUR, tel.
    	no. 6177848123.  Sanyo America can be reached at 2016412333,
    	but Sanyo will not sell you one-sy two-sy quantities. They will
    	however, direct you to a local distibutor that does sell in
    	small volume.

        Looks like their 2/3C is what other folks list as a 1/2C. 600 mAH
        ~ 1/2 (not 2/3) * 1200mAH by my arithmetic. At any rate, my old
        cells are about an inch tall, which would match the 26mm
        dimension. Thanks. 

Its quite common for the "commercial" grade of cells to be a
repackaging of one or more smaller sized cells.  For instance,
the commercial grade of D-cell is merely a C-sized cell in a
larger package.  The tip-off is that the commercial cell will be
rated something below the industrial grade cell.  In the case of
the D-cell, it would be rated at 1200 mA, rather than the correct
1600 mA (or 1800 mA as some are rated today).  If the cell does
not bear a rating, it will have the instructions to charge at a
certain rate for 15 or so hours. Multiplying that recommended
rate by 10 will give the capacity of the cell. 

    Dan,
    	Have fun in Pa and be sure to find out all you can about the
    new higher capacity batteries.  It seems to me that they should
    be worth considering and I have no batteries now to use in my winter
    project.  I don't buy the talk that they won't increase run times
    in a plane.
    
    Charlie
    

>    project.  I don't buy the talk that they won't increase run times
>    in a plane.

    Charlie,

    I have been using the 1700MAH Sub C cells for a month or so, now.
    I used them in the ECub at the fun fly we had.  I don't know who
    told you that they won't increase run time.  Thats totally false.
    The *REAL* problem with them is their increased internal
    resistance.  As you no doubt know, probably better than me, this
    limits the amount of current the battery can deliver, it also
    results in higher losses due to internal heating, and also de-rates
    the life of the cell.  With electric planes, particularly those
    flown with cobalt motors, the draw on the battery (with 05 motors)
    can be anywhere from 13 to 20 amps, so an increase of a MilliOhm
    or so (which I believe is the increase over the 1200SCR cells) can
    mean an additional loss of better than 10 Charlies, uh, I mean
    Watts.  The added capacity more than makes up for this loss, so if
    your not really pushing the cells real hard, you do indeed see
    almost a 3 minute increase in run times (thats what I get with the
    Cub, anyway).  The Electro-Streak, with a 7 turn Cobalt should
    yield the same results.  If you use a 6 Turn motor, though, you
    may find that the cells just don't deliver enough to make a
    significant difference in performance over a 7 Turn motor, and
    they'll get one h*ll of a lot hotter.


    Randy (8^D)

    Randy,
    	I agree with you that the batteries could have a heating problem.
    Also, some planes and cars don't have adequate (or any) cooling
    for the batteries and the motors.  THe extra energy from these packs
    is bound to heat the motor and battery more and possibly drastically
    shorten motor life.  You can fry eggs on most car motors after a
    normal run.  Add 30% to the run time and you might do damage.
    	The solution might be to have better cooling for battery and
    motor.  This should be easy in a plane, but hard in a car.
    
    Charlie
    

    Charlie,

    Yes to what you said, but you must consider that if you use a 6
    turn motor for higher performance, and then use the 1700MaH cells,
    you will probably see performance poorer than the same pack with a
    7 Turn motor.  As it is, with my 7 turn 05, the pack gets
    noticably hotter than a 1200 pack.  Of course its running longer,
    so that does have a lot to do with it, but also its loosing a lot
    of energy to its higher impedance, ask the pack for more amps, it
    might just fry out on you, it certainly can't give much more than
    I'm already asking of it.  If you are constantly maxing out the
    packs current delivery capacity, you will certainly send it to an
    early grave.

    Randy

    re .14
    
    1 milliOhm x 20 Amps = 20 milliWatts increase.
    
    ajai
    
    

    re .17
    
>>    1 milliOhm x 20 Amps = 20 milliWatts increase.
    
    Sorry, Ajai.  I think you forgot the second 20 Amp multiplier.
    
    power = current squared * resistance = 20 * 20 * 10-3 = 0.4 Watts
    
    This may or not be significant; I haven't been paying attention to 
    the conversation. 

RE: < Note 560.13 by LEDS::WATT >       (Higher capacity batteries)

>              I don't buy the talk that they won't increase run times
>    in a plane.

    I think that enough has been said in earlier replies.  The 1700 mAH
    batteries should last longer as long as you are NOT drawing more
    than 20 Amps (for example, a normal 7 turn Cobalt 05).  If you're
    drawing more than 20 amps (like the Cobalt 05 FAI 6 turn motor),
    they say the internal resistance is too high and shouldn't (can't ?)
    be done.

    By the way - the KRC Electric Fly was GREAT, FANTASTIC, EXCITING,
    (etc, etc, etc) !!!!!  Full details to follow in a note in 387.

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    As Eric observed in note 771.68, perfect weather it was; well, maybe a
    bit chilly here in New Hampshire at the hour Jeff and I flew. 
    
    We quit after a short flight and two long ones because I didn't trust
    the remaining battery capacity.  Back home on the Taylor the indicated
    remaining capacity was 60 mah for the transmitter and 215 mah for the
    airborne; in the cold the airborne battery seemed less robust.  The
    Radio Shack Battery Guidebook (No flames, please.  This book is about
    all I have, and I assume they got their information from someplace
    reasonable.) has some data on the affect of cold on NiCd capacity. They
    have a curve of available capacity at a discharge rate corresponding to
    one hour start to finish; they don't say if that one hour is at room
    temperature or at the data temperature. This curve shows capacity to be
    down to 90% at 0 C and then to follow a line approximately straight
    from (0,100%) to (-20,50%), the last point being 4 above zero F.  I
    didn't note the temperature at the Merrimack field, but it was well
    below freezing; I have no idea what the battery internal temperatures
    might have been.  These batteries are very old and might have a
    different loss of capacity with both cold and age; I assumed that they
    would die during a fourth flight just as soon as the plane was at
    altitude and going towards the mountains. 
    
    For a sequence of flights that in aggregate would last longer than my
    batteries, I can swap the airborne pack, but the Futaba transmitter
    presents a problem.  If the charging jack were truly in parallel with
    the internal battery pack, I think I could simply add an external
    battery before the start of a flying session, but the charging jack is
    disconnected when the transmitter is turned on.  I can change that if I
    wish, and I realize that the stronger battery would start to charge the
    weaker and that the total capacity would usually be less than the total
    of the two.  Alternatively, I could add a different jack of a type that
    would, in effect, replace the internal battery when the external one
    was plugged in.  Before I change anything with my soldering iron, I
    seek advice.  What do you do when you have one plane, one radio, and a
    chance to fly for hours? 

    It happens that where and when I fly that I always have my truck nearby
    with its infinite supply of 12 volt power.  I just put together a
    regulated DC power supply that uses this 12 volts as a source and
    provides an output of up to 1.5 amps that can be varied from 1.25 to
    10.5 volts.  With only a little more effort, I should be able to
    substitute this for my transmitter pack when I don't trust the pack
    and don't have time to recharge it at a safe rate.
    
    Before I do it, is there any reason why I shouldn't?
    
    I can think of one reason myself: the electrical path from truck to
    radio is a delicate umbilical cord --- disconnect something and
    the radio dies instantly, soon to be followed by ........

    	What I would do instead is build or buy a peak detecting charger
    and give my battery a 2C charge.  THis would take 30 minutes to
    fully charge the battery and it wouldn't hurt it any if the peak
    detecting is done right.  THe other method is to use a load to
    discharge the battery to about 1 volt per cell (essentially dead)
    and then give the pack a 30 minute charge at 1 amp.  THis will give
    you a good 80 percent capacity charge without the peak detecting.
    	By the way, if your batteries are good, you should get about
    2 hours on a charge in a normal 4 channel setup.  If cycling indicates
    less than 1.5 hours of run time at 250 ma, I would junk the batteries
    and put in new ones.  At least, they should be cycled and watched
    closely.  I have a couple of packs that won't give me more than
    50 percent of rated capacity after repeated cycling.  I use them
    to run my electric fuel pump.  If that fails, I have a mechanical
    backup.  Normal cold weather during discharge should not reduce
    capacity much at the discharge rates the flight batteries work at.
    It's not good to charge at low temperatures acording to the GE Nicad
    Book.

A couple of years ago it became "Fashionable" to use external battery packs 
transmitters at my local RC Car club.  Most people had old sub C cells that
were no longer any use in the cars but could push out 100ma or so for a 
transmitter.  Eight cells in series was quite sufficient to power the 
transmitter, giving 9.6v.  If you really want more then use 9 or ten cells.

After a while there were concerns that the power leads could be contributing 
to interference although we never had any proof of this.  Some sort of 
de-coupling capacitor at both ends would make sense if this was a concern.  To
overcome the risk of breaking the umbelical why not keep the inboard transmitter
cells and make up a circuit so that they "take over" if the external pack 
get removed?


As a footnote we banned the use of external packs because of the possibility
or interference, the problems if someone was silly and made up a pack with 
more than 10 cells (nominal 12v) and also the danger of the external pack 
shorting out, as they were often in trouser pockets!  These may seem trivial
but the average buggy driver struggles to get an IQ into double figures.  As an
organiser of race meetings I often get phone calls from people trying to book 
in.  We only accept postal entries, but here is an example.  It was a call
made to my home yesterday afternoon, taken by my wife.

Caller:  Can I book in to the meeting on Sunday?

Wife:  Do you mean this coming Sunday or the 22nd?

Caller:  The 22nd.

Wife:  Can you send us an entry form?

Caller: I havn't got an entry form.

Wife:  Can you write the details on a piece of paper?

Caller:  I havn't got a piece of paper.

Wife:  Could you get one? (thinks.  I wonder if he can write?)

Happy New Year!

Rob,  bbk Racing

re  response in Note 53.7 to a lament in Note 53.6
    
>>  .................. responding to your comment about not being able
>>  to use your starter on other batteries because of the banana plugs.
>>  What about attaching the receptacle for a banana plug to an alligator
>>  clip? Just unplug from the panel, plug on the clips, and you can
>>  use almost any set up. ... [followed by a description of one approach]
    
    Brass tubing with an ID of 5/32 is a female mate to a banana plug.
    Cut off a piece 5/8th long and solder it to whatever you wish, such
    as an alligator clip or a battery clip or a test lead probe or ....
    This tubing, with an OD of 3/16ths, is a standard size, readily 
    available in three foot lengths.  I have used this technique to
    get one-to-many adaptability in test leads and R/C equipment.
    
    Some alligator clips have similar [but split] tubing built into
    the cable attachment provisions.  For these clips no additional
    brass tubing is needed; if this hole is slightly too large, the 
    built-in tube can be crushed slightly or else opened and wrapped
    around a brass tube and then soldered.
    
    A piece of this brass tubing one and a half inches long and covered
    with heat-shrink is a male-to-male banana connector.

    My transmitter pack needed to be replaced, and someone, Charlie Watt?,
    suggested buying two Sanyo airborne packs from Tower and making a pack.
    I did just that, and experience will tell.  The new pack has two
    to three times the capacity of the old.  The cost was $20.
    
    The conversion is utter simplicity.  Cut the shrink wrap, unfold
    the still connected cells, and wire the two subassemblies together.
    
            +------------+ +------------+ +------------+ 
            |     A3     |U|     A2     |U|     A1     |____________
           (+------------+ +------------+ +------------+ 
           (+------------+                +------------+ 
            |     A4     |_____X----------|     B1     |
            +------------+                +------------+)
            +------------+ +------------+ +------------+)
            |     B4     |U|     B3     |U|     B2     |
           (+------------+ +------------+ +------------+ 
	   (________________________________________________________

    I used ordinary vinyl electrical tape to bind it into one unit.
    That may have been a mistake; I think I should have used Monocote
    or another covering.  And I did not put a plug in the center hole;
    I kept the old assembly intact as a spare.  Should I put a piece 
    of wood dowel in the middle?
    
    To facilitate the possible use of a spare pack, I put a Dean's
    connector pair between the pack and the connector for the PC board.

    A fellow RC noter asked off line about the meaning of "C/10".  The
    answer is in somewhere in these notes, but I'll enter it here in
    my own words.
    
    C/H is a measure of current --- in particular, the value of a steady
    discharge current that will take a battery of capacity, C, to its 
    knees in H hours.   The capacity of the battery will have been stated
    by the manufacturer in Ampere Hours (Ah) or in milliampere hours
    (mAh) and is reasonably invariant for that product.  For example,
    a Sanyo AA size cell has a capacity of 600 mAh; if we draw 200 mA
    from the battery to power a receiver, it will die in about 3 hours;
    600 mAh = 200 mA * 3 h; C/H = 600/3 = 200 mA.  If a servo were to
    jam and the current drain were to double, the battery would die
    in about half the time.
    
    Although C/H is defined in terms of a *discharge* current, it happens
    that it is a useful measure of current in the *charging* process. For
    example, C/10 is a common NiCad charging rate for all sizes of common
    NiCad batteries, no matter what the pack voltage or physical size.
    Bigger cells will have bigger values of capacity and hence bigger
    charging currents, but if you divide that rated capacity by 10, you
    will have the recommended charging current. 
    
    Ahh, you are confused.  Sanyo says to charge their pack for 15 hours,
    and you point out that 15 isn't equal to 10.  That's right, and the
    explanation is in the inefficiency of the battery and the charging
    process.  You can't get out as much energy as you put in. 

>    Ahh, you are confused.  Sanyo says to charge their pack for 15 hours,
>    and you point out that 15 isn't equal to 10.  That's right, and the
>    explanation is in the inefficiency of the battery and the charging
>    process.  You can't get out as much energy as you put in. 

    Sure you can, you just get some of it as heat, and it takes a *REAL*
    long time to squeeze those last few electrons out.

    The real reason that Sanyo, and others, rate their cells for a C/15
    cycle is because this is the charge rate that the cell can sustain
    indefinately wihtout danger of explosion or fire.  Charging, like
    Discharging, creates heat inside the battery.  The heat, as heat is
    prone to do, causes expansion inside the cell.  Expand too much and the
    cell vents (losing precious electrolyte), as well as deforming it's
    internal structure.  Both result in a loss of efficiency in the battery.
    Heat it enough and it goes *POP*, sometimes quite violently.

    ANY NiCad can be fast charged, even slow charge ones.  The key is simply
    that the cell cannot be charged at a rate that will result in excessive
    internal heating.  You can charge at a rate that either doesn't heat the
    battery too much, or you can charge at a high rate and just shut off the
    charge when the battery starts to get hot.

    The proof is in the pudding, so to speak.  The SCE and SCR cells I use
    in my planes quite clearly state 14-16 hour charging is required, yet I
    routinly charge them in 15 minutes.  I have read about people who
    succeed in charging these types of cells in 8 to 10 minutes using pulsed
    current of an even higher rate.

re  Note 53.71, comments by Randy on my tutorial in 53.70
    
    I'm pretty much in agreement with Randy as can be seen in 790.4 
    (It was a reviewer of the draft for 790.4 that prompted me to enter 
    the tutorial on C/10.)  And Randy is way ahead of me on fast charging.
    
>>  > You can't get out as much energy as you put in. 
    
    I should have said "electrical energy".

>>  The real reason that Sanyo, and others, rate their cells for a C/15
    
    Did you mean "C/15" or "C/10"?  C/15 is more often a safer rate
    than C/10, but most of what I've read routinely recommends C/10.

    People who aren't into this stuff should be warned that C/15 is not
    conceptually the same as "C/10 for 15 hours".

>    Did you mean "C/15" or "C/10"?  C/15 is more often a safer rate
>    than C/10, but most of what I've read routinely recommends C/10.

    I just finished reading your OTHER note on batteries.

    Yes, I do believe I intended to say C/10, but was thinking, at the time,
    of 14 to 16 hours, so instead, erroneously typed 15.

    I want to thank ALL contributors to this note and replies. I intend
    to extract the whole thing and read everything CAREFULLY.  I can't
    tell how long it took to read this whole thing on the tube!!!
    The reason I am so thankful is because I have had a devil of a time
    with the Ni-Cad pack in my Panasonic Cancorder.  I bought an extra
    battery when I got the camera (total=2) about a year ago and just
    in Late Feb 89, I found one of the packs dead.  I then bought another
    and while filming a major event, my mother-in-law's 95th birthday,
    I found I was only getting about 20 minutes of service out of each
    pack, when I should have been getting 2+ hours. These packs cost
    in the $65.00 to $70.00 range, so needless to say this is NON_TRIVIAL.
    I intend to read all the replies carefully and make sure that I
    understand the care and feeding of Ni-Cads better than I do now!
    I opened up the "dead" pack and I think, based on some of the 
    replies, I could replace the internal cells a heck of a lot cheaper
    than the cost of a new pack.   Thanks again.
    
    Chuck
    

    Note 594 in the Electro_Hobby conference is germane to Eric's
    plaintive 53.75 here.  The battery is described as a gel cell.

    
    Lead acid batteries HATE being deep cycled, in fact doing so kills
    them off rather quickly. 
    
    
    						Dave
    

    re :-1  Eric is right.  Now is the time to test your nicads before
    risking long flying sessions with old ones.  If you have a cycler,
    cycle them and chuck them if they are starting to lose capacity.  If
    you don't have a cycler, borrow one or have someone cycle them for you
    or chuck the batteries if they are three years old or older.  I've
    seen lots of crashes due to battery failure.  By the way, this is one
    place where PCM is a liability instead of an asset.  The PCM receivers
    die if one cell fails where the non-PCM ones will operate with only
    three cells.  PCM receivers also pull higher currents out of the
    battery pack.  Some PCM receivers have a fail-safe battery warning that
    shuts the throttle before you lose control but I can show you battery
    discharge curves that show that you might not even have time to land.
    The voltage can drop from marginal to fatal in less than a minute.
    
    The bottom line:  CHECK THOSE NICADS NOW 
    
    Take Eric's advice - REPLACE suspect packs.  I use them for non
    critical applications like running my fuel pump or my walkman.
    Don't replace one cell in a pack and trust it in a plane either.  THis
    is false economy.  Old and new cells don't mix well when you charge and
    discharge them in series.  By the way, the least expensive way to 
    replace the receiver and transmitter packs is to buy receiver packs
    from Tower and build custom packs out of them.  They are usually about
    $8.00 for a 600 maH receiver pack.  THat means you can replace a
    transmitter and receiver setup for $24 or so.  Well worth it when you
    consider what happens if your transmitter or receiver pack fails in
    flight.  
    
    Charlie

    Eric,
    	I just purchased the new JR PCM 10. It has a quoted run time
    for the TX of 3HRS.  I can't understand how they can get this much
    time. I haven't got the radio yet but it must have one big mother
    battery pack.
    	The system is nice, comes with five 4031 servos and a 1000ma
    battery. Interesting also is that this 1000ma pack is supposed to
    be smaller than a standard 700 ma pack. JR must be doing something
    different. What it is I have no idea.
    
    
    Tom

VNS TECHNOLOGY WATCH:                           [Mike Taylor, VNS Correspondent]
=====================                           [Littleton, MA, USA            ]

     ELECTRIC CAR SHOWDOWN IN PHOENIX -- ZINC-AIR BATTERY WINS
            {By Rick Cook, Popular Science, July 1991.}

    Zinc-air batteries got a sharp boost in the competition to power the
    coming generation of electric cars this April; a car running on the
    new batteries blew the doors off the rest of the field in an
    electric stock-car race.  In the Electric 200, a 200-kilometer (124
    mile) race at the Phoenix International Raceway in Arizona, a
    modified Honda CRX coupe powered by zinc-air batteries breezed into
    first place, completing 108 laps in two hours and finishing four
    laps ahead of its nearest competitor.

    Solectria Corp., an Arlington, Mass., electric vehicle company,
    entered two of its production cars, one which placed second.

    Sponsored by Southern California Edison Co., Arizona Public Service
    Co., and battery-maker Dreisbach Electromotive, Inc. (DEMI), the
    winning car was put together in less than two months for $90,000. 
    It was intended as a demonstrator for a new generation of zinc-air
    batteries.

    (photo caption reads," A Honda CRX laps the field at Phoenix
    International Raceway(top); an electric motor mated to the car's
    five-speed transmission gives a top speed of 87 mph.  LCDs show the
    battery condition(above).")

    In the last three years, zinc air cells have gone from being
    completely unsuitable for electric vehicles to being among the
    hottest battery prospects for practical electric cars.  There is
    still a lot of work to be done, notably improving battery life and
    power output, but zinc-air's backers are confident the goals can be
    met by the end of the decade.
    {This is an extract, submitted by Jon Hill, Littleton.}

    
    
     a friend of mine has an old Kraft (9years old) and needs a Rx battery
    pack. I belive the Rx has a 4 pin contact. Does anyone have an idea
    on how to fix this problem? (buying a new bat. pack and hooking it up
    to an old 4 pin Rx).
    
    I would like to talk him into buying a new radio sys. I'm afraid if 
    he buys new batteries (12) and a charger then it doesn't work he'll 
    be out the cost of the batteries and charger!

    Older servos had a center tap on the voltage, resulting in 4 wires in
    the wiring harness. The 4 wire plug on the old Kraft rcvr. is
    compatible with the old servo wiring.
    Connecting a new batt. across the plus and minus pins of the rcvr.
    will power-up the rcvr. itself. What would happen if you connect
    new servos is harder to say as it depends on additional factors
    such as pulse polarities, etc.
    
    Yet another case of where buying a new radio is by far the best route.
    
    Terry

    If he's looking at one of the places that do the 1991 conversion, he'll
    end up spending enough that he could get a $100 Futaba Attack and find
    out if he wants to get serious about it. There are also several options
    in the $130 range that give more features/flexibility.
    
    Tower sells battery pack cheaply and he can use his old pack's
    connector. Do your best to discourage this if you can. It's not really
    saving him anything going that route and if he stays in it he'll have
    to change at some point.

    Hi All,
    
    Battery management is a religious topic.  For those of you that study
    this
    religion, there is an interesting article on
    
    
            http://www.cadex.com/cadex/art_2.htm
    
    In summary, GTE believes that not only should batteries be cycled, but
    they
    should also be "deep discharged" to "recondition" the batteries.  None
    of the
    current units on R/C market "deep discharge (0.2-0.4 volts/cell), but
    there
    are many that exercise the batteries down to 1.1v/cell.
    
    The article also states that "memory" is a thing of the past, but that
    the
    real issue is crystal growth inside the cells.
    
    This article re-affirmed (for me) my current practices.  I cycle my
    batteries a few times a year.  The purpose of the cycling is not to
    "erase memory", but to insure that I have not developed a bad cell from
    vibration, over charging, or simply fatigue.
    
    Note well their charts on battery replacement!  They replace 3 times as
    many batteries if all they do is charge them as they do if they are
    exercising
    them!!
    
    Cheers!
    jeff