Conference vicki::boats

    
      The best (and most complete) charge is a slow charge. The very
    best SLOW charge is ~1 amp. The amount of time needed can be figured
    by the amp/hour rating of the battery. A 1 amp charger should be
    left on the battery - 1 hour for each amp/hour of battery capacity.
    So a 80amp/hour battery should be charged for 80 hours with a one
    amp charger.
      It's better if the water is topped-off FIRST, then recheck after
    charging.
    
    					Kenny 

re -.1:

Actually, battery recharging isn't 100% efficient. More amp-hrs must be 
returned to the battery than are taken out.

    THE METHOD THATS WORKED BEST FOR ME, IS TO:
    
    1. DISCHARGE THE BATTERY COMPLETELY, AN OLD HEADLIGHT WILL
       DO IT.
    
    2. FILL WITH DISTILLED WATER TO THE PROPER LEVEL.
    
    3. USE A CHARGER THAT PUTS OUT ABOUT 1/10TH THE TOTAL
       AMPACITY OF THE BATTERY. 100 AMP BATTERY USE A 10
       AMP CHARGER.
    
    
    WHY DO THIS, IN STORAGE OVER WINTER A BATTERY MAY HAVE
    THE TENDENCY TO SULFATE, IT TAKES THE SUPHUR FROM THE ELECTROLYTE
    AND DEPOSITS IT ON THE PLATES. WHEN YOU TAKE IT ALL THE WAY
    DOWN, YOU ARE REASSURING THAT YOU HAVE TURNED OVER ALL THE ELECTOLYTE
    AND GOTTEN THE SULPHUR BACK INTO THE SOLUTION. TAKE A HYDROMETER
    TO IT TO MAKE SURE THE CELLS ARE ALL EVEN, OR ARE CLOSE.
    IF ONE IS A LITTLE OFF, DISHCAREGE AND RECHARGE AGAIN.
    
    JIM.

re .3:

I strongly disagree. Fully discharging a lead-acid battery will
certainly greatly shorten its life. Most deep-cycle batteries will
survive very, very few complete discharges (under 10 usually). If
half-discharged, the usual life is several hundred to a few thousand
discharge-charge cycles. As the amount of discharge before recharging
goes down, battery life goes up dramatically. 

    
    Do not run a battery down to a 'dead state'. Batteries last longest
    when they are kept at a charged level!
    
    Repeat - do NOT run battery down to 'dead' - this applies to deep
    cycle and to high cranking batteries!
    
    

    
    The year before last I left my battery in the boat, in storage all
    winter.  The dealer who pulled it out of storage said it was completely
    discharged (not a real surprise to me).  He SAID he re-charged it,
    and since the engine was warm when I picked it up, I believed he
    had gotten it running.  Well when I went to start it for the first
    time it was dead,  I was not happy.  I took it back to him and he
    put it back on the charger and did some sort of HIGH amp charge.
    He said that it would actually vibrate the plates and bubble the
    solution.  He felt the vibration would get the deposits off the
    plates.  Well,  I never had a problem with it for the rest of the
    season.
       
    So, in my case the slow charge was not what was needed.
    
    Of course time will only tell  how this has effected its lifetime.
    By the way I use the boat on an average 3 times a week so it gets
    alot of use,  and the charge is regularily refreshed.
    
    /Mike
    
     

    
      Re .6
    
      It's not that a slow charge wasn't NEEDED for you (it was - it's
    ALWAYS the best way to charge) but the dealer NEEDED to give you
    a fast charge to get you on your way!
    
      As far as expected life from lead-acid batteries is concerned
    I looked up the following in a battery book:
    This gives a good idea of how a lead-acid battery will respond to
    discharges.
    
    	Expected life  -  100% discharge/charge cycle --> 200 cycles
    
    			  25% discharge/charge cycle --> 2000 cycles
    
    	This data is for a "Deep Cycle" type lead-acid battery.
    
    				Hope this helps,
    				Kenny

    I've always been confused about what to do with a battery(s).
    I've heard many stories about keping them up, and how to store them
    for winter. My last boat was 28 ft., with 4 Surrette batteries.
    They were a pain i the a$$ to get out, and back in. With the
    advice of an old timer, i've been leaving them aboard for winter.
    For winter storage, i check them with a hydrometer, add water
    if needed, hit the charger for the time required, using the 
    amp guage on the front as a judgement tool, and finally disconnect
    the positive side. I've been doing this for 2 seasons and
    have not had a problem. In spiring i follow the same process.
    
    I've spoken with the Surrette factory, and several of their retailers,
    their recommendation for low cell conditions, or uneven cell
    conditions is to discharge to (dead) and recharge 3 times.
    This shakes the sulfur off the plates, and in most cases
    will return those cells to normal conditions. If they don't
    have a problem, don't try to fix it.
    
    
    you decide, and your milage may. By the way Surrette claims
    their ruuber cased batteries are 12-15 year batteries.
    I'm close to believing it, my old boat is at my marina,
    it has a 10 year old in it and still going strong.
    
    jim
    
    
    

    These battery notes don't answer some basic dumb questions:
    
    1) Why does my owner's manual say to remove the battery from the boat
    in the off season and keep it from freezing?  I don't keep my car
    battery from freezing in the Winter and never had a problem.
    
    2) I take it (although no one has clearly stated it) that storage
    batteries will in fact discharge over the Winter.  Hmm, a $1.29
    Eveready D cell won't lose more than a couple percent of charge in
    six month storage,  What gives?
    
    3) Assuming that expensive lead-acid batteries do poop out over the
    Winter, what's the difference between giving them one good charge
    in the Spring or periodically charging throughout the Winter, as
    recommended?
    
    
    

    
      The answer to your first question is actually contained in the
    second question...  The battery won't freeze if it's fully charged,
    but as it discharges, it becomes more and more prone to freezing.  
    There should be no problem with leaving it out all winter if it's
    frequently charged.
    
    
    							-al
    

    The battery won't freeze if kept charged... but it should be recharged
    about once every month to six weeks. A lead acid (car/boat) battery
    is subject to self discharge due to local action on the plates. Due
    to impurities in the lead/leadperoxide plates tiny cells which nucleate
    around impurities slowly discharge the battery. Lead acid batteries
    hate being run down all the way or left discharged for any length of
    time.  To lengthen their life to the max. avoid complete run downs and
    keep them charged.  During storage don't store the battery on a
    concrete floor... put a piece of wood under it. The concrete seems to
    make the battery run down much faster... the wood avoid it.  It also
    makes good sense to disconnect the terminals from the battery during
    storage.  You don't want a tiny electrical load somewhere to run your
    battery down even faster, or the accelerated terminal corrosion, or
    a SHORT. 
    
    Also store the battery in a cool/cold place... it will self discharged
    slower because of slowed chemical activity due to the cold.
    
    Jeff

    Oh yeah, a battery will freeze if discharged because as part of the
    normal operation of the battery when discharging acid gradually changes
    to water.  That is why one can tell the state of charge with a
    HYDROmeter which measures the specific gravity of the acid. That 
    doesn't mean that a flat battery only has water for electrolyte... but
    it is far more water than acid when flat. 
    
    Jeff

    re:  .9,,,
    
    Here's a stsory from my old buddy that was in the Marine Bus.
    for 45 years.................
    
    We're down the marina in the spring, i hate all the lugging and
    loading you have to do.  THEM FRi,.,,...,m,m batteries are
    dam heavy, i ruin clothes, i hate it, i hate it, i hate it...
    enough.
    
    I have 5 batteries, 2 are 6 volt.
    
    Here's my buddy, runs a hose over to his boat, climbs in
    and fires it up... Hey when the hell did you put in those batteries,
    about 3 yrs. ago.
    
    OH yeh, your one of those dumb sh....s that lugs them out every
    year.  MADE ME FEEL REAL GOOD.
    
    Here's what i've done since, 1983:
    
    charge them up well before you put the covers on.
    
    disconnect the + cable.
    
    LEAVE THEM ALONE.......Don't make work for yourself...
    
    JIm

	As long as you get it (them) all charged up before the end of 
the season (say, mid december ?) then it (they) should hold plenty of 
charge for when you launch in the spring (say, mid March).

	One other  *_MINOR_*  possibility is that if the battery is in
some kind of a well and if the drain from that well isn't completely
clear it is possible that the battery could be crushed by ice forming
*_AROUND_*  (not inside)  it.   How could this happen ?    Awww, all 
those leaves blowing around the yard right now - and if you leave the 
cover off and it rains a lot ,,, and if and if and if and if and if

	R

    One secret for getting a lead acid battery to hold a charge for a long
    period is CLEAN.  A slight oil and salt residue on the surface of the
    battery can provide an electrical path from + terminal to - terminal
    (or is that - to + ?).  A mixture of baking soda and water is the
    recommended solution (ugh, pun).  Try not to get this stuff into the
    venting system of the battery, as it will neutralize (discharge) the
    acid.  
    
    Carl
    

    re .13  The point is not REMOVING the battery(ies) from the boat. The
    points are:
    
    1. Disconnect the cables.
    2. Clean the cell tops.
    3. Charge them up completely before storage.
    4. If they sit for a long time (say over 2 months in a warm climate)
       charge them up mid storage season.
    
    If in New England or a cold climate the monthly recharge is not as
    important because the cold/cool weather will help the battery retain
    its charge.
    
    You didn't say how long the old salt let his batteries sit.  I assume
    it was for Winter storage only (say 3 to 4 months).  Also, the long
    sit with no midseason recharge isn't helping their life any even if
    they do still retain enough charge to start the boat in the Spring.
    
    I bet he was performing (not performing) this storage procedure on
    CUSTOMERS boats.  Not HIS batteries.
    

    The other potential gotcha if you leave the batteries in the boat (as I
    do) is that if they do get discharged and freeze, then thaw, the case
    tends to rupture and you wind up with battery acid in the bilges or the
    battery box, whatever...
    
    I leave my battery in and charge it every month or two at a two ampere
    rate for a day or so.
    
    Four seasons have gone by now, so the battery gets arbitrarily replaced
    this spring.  It's cheaper than a tow or worse...
    
    The question asked above and not answered is why not wait until spring
    to charge.  Aside from issues like freezing and rupture, the answer is
    sulfation.  A battery depends on reversible chemical reactions to
    function.  The primary limit to battery life is the formation of large
    crystals of insoluble lead sulfate on the plate surfaces.  This PbSO4
    passivates the plates by growing and tending to shield the lead from
    the electrolyte.  Letting the battery leak down or self discharge for a
    few months encourages this aging process.
    
    J

    I think its good PM to routinely replace your batteries if you can
    afford it.  But if you do a few tests you can tell how healthy your
    batteries are:
    
    1. If the battery never tops up charging, i.e. the battery keeps
    drawing current from the charger even when it should be completely
    charged (an amp or two) implies that its not building sufficient back
    voltage to stop the charge. This assumes the charger voltage is set
    correctly.  It should top up and stop drawing current.
    
    2. Excessive gassing when its fully charged... lots of gassing implies
    number 1.
    
    3. Individual cell load tests which put a measured load across each
    cell and measure the current and voltage drop.
    
    4. Hydrometer tests... each cells state of charge should be within 
    10 hydrometer points of each another.
    
    If your battery passes these tests its unnecessary to replace it.
    
    It sounds like alot of work... but with a cell load tester OR
    hydrometer you can save yourselve alot of money.
    
    Oh another thing... before you store the batteries... top them up with
    DISTILLED (NOT TAP) water. Charge the battery after you add the water
    so it is well mixed. You don't want a layer of water freezing on top
    of the acid. 
    
    You can pry the cell caps off on many 'sealed' batteries do do the
    water adds and tests. 
    
    Jeff
    

    Re:
    
    my marina owner friend did this to his own boat.
    
    i have done this to my boat since 83. That boat is still
    at my marina, one of the batteries just celebrated a 12th
    birthday. and another its 9th.
    
    What more can I say....
    
    
    If you have a boat, which you store at home, and may have 1 or 2
    batteries, its real simple to remove and store them.
    But mine lives at the marina---------------------------
    
    JIm.
    

    The battery in my boat tipped over and lost 1/3 - 1/2 of the
    electrolite.  I refilled with water, charged it, and used it the rest
    of the season (3 months) with no problems.  Took it out of the boat for
    winter storage and re-charged it up.  It doesn't appear to be fully
    charged and seems to discharge more than normal.  The charge indicator
    in the barrery never is bright green and after a few days off the
    charger it starts to turn amber.  Note: the battery was new (sears) in
    the spring.
    
    I have taken the battery to sears and they put it on their tester and
    say there is nothing wrong it just needs to be charged some more.
    
    My question is :  Is this battery gone or going fast?  Should I try and
    get sears to replace it just in case?  Can I add something other than
    water (battery booster stuff they sell in auto stores)?
    
    I should get my own hydrometer to test it and keep record of discharge.
    Any recommendations?  type with 5 little balls or the type with the
    bulb that reads specific gravity.
    
    Thanks in advance for you help
    
    Gordon

re                       <<< Note 306.20 by PENUTS::GORDON >>>
>                             -< lost electrolite >-

	A similar thing happened to me {translation: I did something 
similar}  I decided that I'd replace them thar H2SO4 molecules with 
some new ones, so I bought some.  I still have lots of 'em {many
billion at a guess}, probably enough to refill a battery - maybe we 
should knock it over again and put new molecules in it this time ???

	Reg	{in Mass, where are you ?}

    When you lost the acid and replaced it with water you lost 'active
    ingredients".  I would recharge the battery with a slow charge < 5
    amps overnight charge.  Measure the specific gravity with a hydrometer,
    it should be about 1.260 at 80 deg F.  If its low (and it will be
    thats why the indicator turns yellow) dump all the old acid out
    (be careful, down the sewer is a good bet) and add new electrolyte which is available for dry charged
    batteries.  The new electrolyte will be approx 1.260.  Actually, you
    can just dump the old acid out, and add the new stuff without
    measuring the sp. grav. first.  But the important thing is to make
    sure you do this with the battery FULLY charged, if you do it at a
    partial charge you will wind up with electrolyte with too high a
    specific gravity which will make it a hot battery but will shorten its
    life.

    Thanks for the help.  I worked for years as a mechanic and never knew
    that you could replace the electrolite in a battery.  
    
    I'm going to try and get Sears to replace it.  If that doesn't work
    I'll try  replacing the electrolite.
    
    re: -2
    
    I'm from Mass and keep my boat in Newburyport in the season.
    
    Thanks
    Gordon
    

    Its possible to take a sulfated battery, dump the acid out. Replace the
    acid with DISTILLED water and give the battery a slow charge for
    several days.  Slow charge = 3-4 amps.  The theory is to drive part
    of the sulfate off the plates into the water and desulfate the battery.
    Then you dump the water out and replace it with 1.260 sp. grav. new
    acid.  
    
    Jeff

    dumping the acid down the sewer/sink/toilet is NOT a good bet, it is
    the height of irresponsibility.  It can damage pipes and valves, or
    could hurt somebody working on the pipes.  
    
    1) Buy battery acid at an auto store.
    2) charge battery overnight.
    3) Pour the acid in a glass or ceramic vessel, then add baking soda
       until it stops fizzing, hence neutralizing acid.  Then you can
    discard it, mindful that you're still sending some lead down the
    drain...
    3) Fill the battery with the new full strength acid immediately after
       draining.
    4) Charge it again.
    
    J

    Ok, I stand corrected on the acid disposal method.  I agree the
    neutralize it with baking soda method is MUCH better.  If one ran
    copious amounts of water down the drain as you poured the 10 % 
    sulfuric down the drain I have trouble believing that anyone would
    be hurt unless there was someone in the cellar with their hands 
    in the fluid draining down them.... sort of a long shot if you ask me.
    As far as the sewage treatment facility is concerned the amount of
    acid flushed compared to the normal voluum of sewage arriving at the
    plant would make the trace of acid you dumped undetectable.  If
    EVERYBODY dumped acid at the same time then I agree we would have a
    big problem...  
    
    If it went into a septic system along with lots of water I have trouble
    believing it would cause serious damage.
    
    Correct me if my views are way off here.
    
    Jeff

RE: Note 306.26 

>> If it went into a septic system along with lots of water I have trouble
>> believing it would cause serious damage.
   
>> Correct me if my views are way off here.
   
You're probably right that it wouldn't do much damage once in the soil,
especially considering the amount of acid that lands on our soil every
time it rains.

But I think your pipes might disagree with your theory of limited damage
to the septic system.  On the bright side, it would probably help you 
locate any weak spots in your cast iron sewage pipes.   8^) 

Rick

    go for it,,,  plumbers need the work..........
    
    8')
    
    
    

    Cast iron is virtually immune to sulfuric acid, especially if its
    diluted acid running through THICK cast iron sewer pipes, PVC sewer
    pipes is immune to acid attack as well.  Any lead used for caulking cast
    iron pipe sections together is immune to acid attack too. Thats why
    the posts on the battery are made of lead.  Sulfuric acid primarily
    would attack organics, such as wood, paper, people, animals.
    
      I expect the risk to a septic system would be in killing beneficial
    microorganisms in the tank rather than plumbing damage... 
    
      As far as municipal sewage plants are concerned as I said before by
    the time the incredibily diluted acid gets there it would be
    undetectable. 
    
      But in these days of environmental damage, I do agree with the wisdom
    of neutralizing the acid with baking soda but not for plumbing damage
    reasons.
    
      Yup, I know the plumbers will love me, but not from acid being dumped
    down the drain.
    
       Jeff

re  (a few back)

	DON'T  ADD BAKING SODA TO THE ACID !


	Slowly add the acid to the baking soda.



	"Why" ?

	'cos if it spits 'n spurts Ya don't wanna the acid spraying 
inna Ya face.

	R

    I remember .-1 rules in re water in acid, because the heat generated by
    acid and water mixing can cause the water to flash to steam, which can
    cause the acid to be blown into your face.  I am not aware of any
    equivalent occurrance with baking soda, although it doesn't sound like
    a bad suggestion...
    
    J

    My son left the radio on in the boat and I moored it for two weeks.
    (Silly me for not having a mooring checklist).   Luckily no storms
    or huge rains so the dead bilge pump didn't matter.
    
    Battery was totally dead.  I recharged it with a cheap Sears charger.
    The charger died after two hours.  The meter was reading about 5.5 amps
    before dying.  I presume this is a bum charger and not the fact that my
    battery was so dead it killed the charger ?!  Nah!   Finished charging
    w/jumper cables from my car.   Battery starts the boat and after
    running many hours during the weekend, the little "charge indicator" on
    the battery is back to green color, supposedly indicating full charge.
    
    This is a "NorEaster" marine battery.  I would doubt that it's "deep
    cycle" or anything expensive like that.  
    
    My question is what kind of condition am I in now?   Has the battery
    life been shortened?  Should I buy a new one?  This battery has to
    reliably run the bilge pump and restart the boat after layup periods of
    several weeks.   Given the hassle of rowing the battery back to shore
    and recharging (not to mention time lost), I'd rather not risk it.  But
    if this incident is no big deal for the battery then there's obviously
    no point in spending the money.  Anyone know?
    
    

    The battery is almost dead. You will find that it will not hold much of
    a charge for more than a week or two.
    
    I've done the same kind of thing myself on numerous batteries...no
    matter how much you know, it just keeps happening. Eventually, I end up
    throwing the batteries away.
    
    Tally-ho,
    
    Ray

    I think it depends...You almost certainly damaged the batery to some
    degree, but it depends on how flat it was for how long. Lead acid
    batteries seem to be able to tolerate a few cycles of being flattened
    if they aren't too flat, too long. It shouldn't be to hard to test
    what kind of amp-hour discharge capability it still has.
    
    Bill
    

    I agree with .34   You certainly have shortened the batteries over-all
    life... but whether you have ruined it can be determined by tests. Do a
    specific gravity check of all cells with a wet hydrometer. If all cells
    are within 20 points of one another i.e. 12.20 mid point with no range
    further than 12.40 or 12.00 you are probably ok.  BUT remember that is
    an example, your mid point could be 12.50 rather than 12.20 as in my ex
    ample. A fully charged battery should read 12.60 to 12.80  A reading 
    below 12.50 indicates it needs a charge.  10.50 is a dead flat battery.
    Whats with all these numbers?  The weight of the sulfuric acid as
    compared to water. A hydrometer is cheap... 6 to 10 bucks at any auto 
    store. After sucking the acid up into the glass tube for a sample
    squirt it back into the cell with through with the reading.
    
    You could also do a discharge test... discharge the battery at say 5
    amps for 5 hours... if the voltage/amperage didn't drop off near the
    end of your test you will have withdrawn 25 amp hours.  Most 12 volt
    typical batteries have capacities inthe 40 amp hour range.. BUT you
    dont want to flatten the battery again during your test.. run it down
    say half way to determine if its ok.
    
    I know I have gone on here but your question does not have a simple
    answer. You must run tests to be sure.  If the tests are too much or
    too much trouble replace the battery.
    
    Jeff 

    I have left the dome light (actually 3 bulbs) on my truck on several
    occassions sometimes from friday pm to monday am. The batery
    has been so dead that even the key warning buzzer does not come
    on. I jump the truck and life goes on. I am not saying you did not
    hurt the batery, but if it was in good shape before hand, I would not
    toss it out for a new one. If its 4 years old then it may be time
    for a relacement anyway.
    
    Bruce

    Actually I just remebered I did the same thing (left the vhf on) on
    my chris one time, same result applied, no noticable problem after
    reacharging.
    
    

    Just tried it after sitting a week.  No problem.  The charge indicator
    still is green (are those things reliable anyway?  How do they work?).
    
    I guess if it's a "healthy young battery" it can survive an event like 
    this.
    

    Have the battery tested.  There's a possibility that it is a "deep
    cycle" battery.  The couple of hours that you got out of the charger
    before it died may have put enough of a charge into the battery before
    you jumped it so the plates wouldn't have warped.  I personally would
    spring for a new battery if I was mooring my boat and had to rely on
    the bilge pump.  Maybe even one of those solar recharging panels if the
    boat was going to be left unattended for awhile.
    Wayne

	I recently (three weeks ago) found that the battery in my Whaler
was ultraflat.  I removed and recharged the battery (2.5 years old) and have 
had no problems since.  I think that there are two key issues. First, the 
relative health of the battery. Second, the condition of the on board charging 
system.  Contact corrosion is what contributed to the recent discharge.

STeve 

re; .38

I had a one-year old sears diehard gold, their best, completely drained.  Radio
left on for three weeks.  This battery always drew 5 amps no matter how long I
charged it.  When use to start boat it gave a short spurt of power then was dead
again.  I took it to sears and they tested it on a large battery test station.
Told me it was bad and pro-rated it, which cost me $12 for a new one.  (Great
deal)

I have run down several other batteries since, thinking "I done it again", but
caught it just before a complete drain and was able to save the battery.

dave

    Is there any problem with putting a deep-cycle and a starting battery
    in parallel through a battery switch?   Presumably you would start and
    run on "both", but switch to the deep-cycle to run the boat while it's
    moored (bilge pump etc).
    
    Since August Maine has had more than 15" of rain.  Between that and
    leaving electrical stuff on my accident I'm getting tired of my single
    elcheapo starting battery arrangement running down.   The alternator is
    a 3/9 job (what does 3/9 mean) integral to my 115 outboard, so even
    when the engine is running I'm not getting a huge charge unless I run
    for a while.
    
    Anything wrong with adding a second battery of a different type?  Do I
    need an isolator?   Doesn't an isolator keep one battery from
    discharging into the other?  If so, does this also preclude charging 
    both in parallel from the integral alternator.   Guess I need a
    quick course in battery setup options - if there is a note in here to
    that end please point..  I looked at all the battery notes.
    
    

I've had a deep-cycle and a non-deep cycle aboard my 24' HydraSports
since 1984. For a variety of reasons, my conservatism being paramount,
they've each been replaced once.

They are wired through a Perko battery switch. I parallel them to start,
then go out on 1 and home on 2. Some days I go out on 2 and home on 1.

A diode isolator would allow you to have both batteries on line at all
times, and still support even charging (there are other issues, but that
about sums it up for purposes of discussion). You'll be drawing from both
batteries all the time.

I opted for the switch versus the isolator simply because I thought the
switch would be more reliable than a diode isolator setup. There hasn't
been any problem with the switch. My dash-mounted voltmeter displays the
voltage of the selected battery.

Art

Have you looked at these notes in MSCSSE::SAILING?

   272   OBLIO::MCWILLIAMS   27-MAR-1986    22  Marine Batteries
   825  SNO78C::ATKINSON      5-MAY-1988    23  12v Charging Questions
   843    SAGE::WALKER       19-MAY-1988    28  Battery Size
   926   CURIE::DONOHUE      25-JUL-1988    33  A Third Battery
  1102   VBV01::HJOHNSON     13-JAN-1989    15  Battery help

The big problem with a diode isolator is that it reduces the charging 
voltage at the battery by the voltage drop across the diodes (about 0.7 
volt). This will result in chronic undercharging which will greatly 
shorten battery life. If you use an isolator, you must have a voltage 
regulator that senses battery voltage, not alternator output voltage (as 
all standard regulators do). 

Parallelling deep-cycle and engine starting batteries is not a problem 
as long as both are either conventional wet batteries or both are 
gel-type (eg, Prevailer) batteries. Do not mix the two types. Also, deep 
cycle batteries are quite capable of supplying sufficient engine 
starting current. See one of the notes in SAILING for some details.

Alan

    Thanks Alan, those notes were a great education in marine power
    systems.  
    
    Sounds like to keep things as simple as possible I buy a deep cycle
    battery (of the same construction as the starting battery, i.e.
    lead-acid) and a switch.  No isolator.
    
    So the normal usage would be:
    
    	Moor on 1 (deep cycle)
    	Start on 2   (or maybe 1+2 - see question below)
        Run on 1+2 to charge both.
    
    I heard that switching load off an alternator can blow its diodes. 
    When switching from  2-only to 1+2 will the switch keep at least one of
    the batteries connected at all times, or will there be a momentary
    disconnect of everything?   If so, would it be better to start on
    1+2 and leave it there while running?   Sounds like if the deep-cycle
    is low, the starting battery may charge the deep-cycle instead of
    flowing into the starter motor!
    
    

re .45:      

>>>    I heard that switching load off an alternator can blow its diodes. 

Probably will, not can. Both Ample Power and Cruising Equipment sell 
special diodes (<$20) that connect across the alternator output to 
prevent this catastrophe. 

>>>    When switching from  2-only to 1+2 will the switch keep at least one of
>>>    the batteries connected at all times, or will there be a momentary
>>>    disconnect of everything?   

Most switches, eg, Cole-Herrsee we have, make before break, so there is 
no problem going from 1 or 2 to 1+2.

I'd suggest using both batteries for starting and only change the switch 
position with the engine stopped. Yes, the more fully charged battery 
will attempt to charge the less charged battery, but this isn't a 
problem. When it comes time to replace the starting battery, I'd suggest 
getting an identical deep-cycle battery. They're a lot more rugged. 
    

    This topic is discussed in pretty good detail in this month's "Trailer
    Boats" magazine.  How to install either a switch or an isolater and
    why one may be better for you than the other given the application.
    Wayne

re                <<< Note 306.44 by MSCSSE::BERENS "Alan Berens" >>>

> The big problem with a diode isolator is that it reduces the charging 
> voltage at the battery by the voltage drop across the diodes (about 0.7 
> volt). This will result in chronic undercharging which will greatly 

	Won't that depend on where the voltage regulator's remote
sense is, across the alternator output vs across the batteries ?
With internally regulated alternators there probably isn't a choice. 

	Hmmmm, I'm wondering if it makes any REAL difference, since 
its necessary to output enough voltage to overcome the alternator's 
own and the battery's impedances.....  I'd guess the isolation diode's 
impedance is trivial compared to these.  The drop across the diodes
drops to almost zero as the battery approaches full charge anyway
(~= zero current). 


	R

Most (if not all) battery switches are make-before-break. So, when
switching from 1 to 1+2 to 2, there is *always* a battery in the circuit.

You go to two batteries for starting to essentially double your current
capacity. After starting you switch to 1 or 2 to charge the battery of
your choice. It is NOT good to leave 1+2 in the circuit because the two
batteries will NOT charge equally. You won't hurt anything, but you won't
be proving the best charge to the two batteries.

Like I said: start on 1+2; go OUT on 1, come home on 2. Can't go wrong.

Art

    
    Unless i read the last reply incorrectly it says,
    
    start on 2 batteries and then after starting to switch to 1.
    
    I WOULDN'T DO THIS, MY SWITHCES SPECIFICALY STATE "DO NOT SWITCH
    
    WHILE ENGINE IS RUNNING" it goes on and says something about
    
    damaging your alterantor or something else.  BUT I WOULD CHECK
    
    INTO IT.
    
    JIm.
    
    

re .48:

>>>	Won't that depend on where the voltage regulator's remote
>>> sense is, across the alternator output vs across the batteries ?
>>> With internally regulated alternators there probably isn't a choice. 

For any standard alternator/regulator, the regulator senses alternator 
output voltage. You'd have to disconnect the sense wire from the 
alternator and connect it on the battery side of the isolator. Depending 
on the alternator/regulator design this may or may not be possible. On 
our OEM alternator, it wasn't. 

>>>	Hmmmm, I'm wondering if it makes any REAL difference, since 
>>> its necessary to output enough voltage to overcome the alternator's 
>>> own and the battery's impedances.....  I'd guess the isolation diode's 
>>> impedance is trivial compared to these.  The drop across the diodes
>>> drops to almost zero as the battery approaches full charge anyway
>>> (~= zero current). 

Yes, it make a real difference. The trouble is, the voltage drop across
a diode is not purely resistance. The voltage across a diode roughly 

     Vd = Vg + current*internal resistance 

For most diodes Vg is roughly 0.7 volt, though it can be as low as maybe
0.4 volt. For voltages less than Vg, the current is very small, usually
in the range of .001 to .01 amps, which is less than the recommended
trickle charging current for a battery. The internal resistance is quite
low, so that normally Vg is greater than current*internal resistance. 

There normally some (at least an amp or two) current being drawn from the
alternator to run electronics, etc. So, if you use an isolator without 
modifying the regulator to sense battery voltage, the batteries will be 
always undercharged since the voltage across the batteries will be 
the alternator output voltage minus Vd. A battery may eventually reach 
full charge with a small charging current, but it could well take days, 
which is not particularly practical. 

One last point, the current going into a battery depends on the voltage 
across the battery imposed by the charging source. If this voltage is 
high enough, there will charging current no matter whether the batter is 
fully charged or not. Charging current reaches zero only when the
charging voltage is less than the fully charged voltage of the battery,
in which case the battery will never be fully charged. 

re .49:

Actually, charging both batteries at once works well. The more 
discharged battery gets more charging current, which is exactly what you 
want. The only potential problem with charging two or more batteries, 
whether you connect them in parrallel using the battery switch or use an 
isolator, is when the batteries are so deeply discharged that the 
charging current drawn causes the alternator to overheat and perhaps 
self-destruct. Most alternators do not have current-limited output and 
will supply enough current to self-destruct under the right (wrong) 
conditions. Our non-OEM alternator will supply 100 amps at a (quite 
safe) alternator case temperature of 200 deg F. Most OEM alternators 
can safely supply only maybe 80% of their rated output continuously. 

One advantage of specialized charging systems from Ample Power, Cruising 
Equipment, etc, is that they will fully recharge a large battery bank in 
an hour or less, which is very important to those of us who run our 
engines only when the wind isn't blowing. 

Alan

    Re .5 (That's a no-no)
    
    Not necessarily. It depends on the type of switch. The less expensive
    ones are break before make - and with them, its a no-no. The make
    before break (more expensive) are made specifically so that one
    can safely switch between 1, 2, and 1-2
    
    The Cole-Hersee switch on the ambulance that I drive is of the latter
    type and you are specifically warned (on the switch) not to turn
    it to the "OFF" position with the engine running.
    
    Bill
    

    Aren't there "self energizing" alternators that wouldn't be effected by
    a shut down?  Trailer Boats magazine has an advertisement for a 
    "Delco style" 62 AMP marine alternator with either a 3 wire or 1 wire
    connector.  I would assume that a 1 wire connector alternator must have
    a built in regulator to supply power to the fields coils (not sure of
    my terms here).  The 1 wire coming out would be the output lead.  Seems
    to me that this type of alternator would be immune to break before make
    switches blowing the diodes.  Or does disconnecting the output lead 
    cause the blowing of the diodes?
    Wayne

    Since we're discussing alternators, does all the above (blown
    alternator diodes, etc) apply to an outboard with an integral
    alternator?   The specs say my Johnson 115 has a "3/9" amp alternator.
    What does 3/9 mean.  In any case 9 amps isn't much of an alternator
    which says to me that my proposed dual battery setup is more of backup
    strategy than one in which either battery is regularly discharged
    significantly, i.e., we're talking many hours of running time for even
    a minimum recharge.

re       <<< Note 306.54 by TOOK::SWIST "Jim Swist LKG2-2/T2 DTN 226-7102" >>>

>    Since we're discussing alternators, does all the above (blown
>    alternator diodes, etc) apply to an outboard with an integral
>    alternator?   The specs say my Johnson 115 has a "3/9" amp alternator.
>    What does 3/9 mean.  In any case 9 amps isn't much of an alternator
>    which says to me that my proposed dual battery setup is more of backup
>    strategy than one in which either battery is regularly discharged
>    significantly, i.e., we're talking many hours of running time for even
>    a minimum recharge.

	Well, it  DOESN"T  mean that it puts out 3 volts here and 9 
volts there, so you get 12 altogether (-:   I'd guess it means one of a 
few things

a) 3 amps continuous, 9 amps max  

b) 3 amps from one winding (for ignition, typically), 9 amps from
another winding (typically for other parts of the boat, accessories,
etc.) they may do this partly to keep ignition noise away from
whatever electronics you may run. 

c) 3 phase - 9 amps (least likely to be right)

	As I said, these are guesses.


	Reg

re .53:

I am not familiar with "self-energizing" alternators, but, just a guess, 
they have a permanent magnet that is used to generate enough current to 
supply the field windings. The current through the field  windings
creates the magnetic field that is used to generate the alternator
output current. Varying the current (usually supplied by the battery)
through the field windings controls the alternator output. 

The current through the output windings also creates a magnetic field. 
When the output current suddenly becomes zero, this magnetic field 
collapses and creates a large reverse voltage spike in the output 
windings. It is this voltage spike that blows the rectifier diodes. I 
would assume that self-energizing alternators would have this failure 
mode. 

Both Cruising Equipment (6315 Seaview Avenue, Seattle, WA 98107) and
Ample Power (1150 NW 52nd Street, Seattle, WA 98107) sell devices that
reduce the magnitude of the spike enough to prevent diode failure.
Cruising Equipment claims that with their device removing the load from
an alternator producing 100 amps will not cause any damage. The one from
Cruising Equipment looks more rugged physically and is easier to
install. Both devices are under $20 as I recall. Cheaper than repairing
an alternator. 

    As far as I know 'all' alternators of the marine and automotive types
    are 3 phase (3 electrically distinct windings) with the 3 phase output
    rectified by the diodes to DC.  During one revolution of the field
    windings a three phase waveform is generatated with the voltage peaks
    120 deg. ahead/behind the adjacent phase.  The 3 phase setup which is
    similiar to commercial power generators improves the efficiency of the
    alternator and the low RPM output of the alt. enormously. Thats why
    the traditional DC gen was done away with in autos/boats in the 1960's.
    
    Jeff

    I thought I would enter my question here first rather than starting a new
    file. Although it has to do with batteries not recharging specificaly.
    
    Over the years I have added additional electronic devices to my boat (fish
    finder, phone, VHF).  My concern is being out in the middle of the lake 
    with the VHF, fish finder, phone and radio on and not being able to start 
    the boat.  My questions are these:
    
    1.  Should I not be concerned since the amount of power coming off the
        battery is not enough to hurt?
    
    2.  Could I get by with just running one device at a time?
    
    3.  Should I concider putting in a second battery?
    
    4.  What do I need to put together a two battery system?
    
    Thanks 
    Rick

    Rick,
    You need to come up with some numbers for anyone to help answer your
    question.  Specifically, what is the output of your alternator? The
    reserve capacity of your battery?  The current draw of all the
    accesories you use (both an average and worst case situation). Which
    ones are run while the engine is shut off, and how often do you stop 
    and restart the motor (draining the battery)?
    
    Some outboards only put out like 6 or 9 amps max.  Inboards on the
    other hand may put out 50 or 60.  With a smaller outboard, if you're
    running several accesories at once you can actually discharge the 
    battery even while the engine is running.
    
    You can work all kinds of magical formulas to find whether your OK. 
    But nothing is foolproof (because fools are so ingenious) so the only
    way to be truly sure you won't be left stranded is to install the
    second battery and isolator.
    
    Rick

    Yup, we need numbers to answer your question.  It sounds as if you
    have low current draw items though.  Another question is HOW LONG
    do you sit with the engine off with the devices on?  I will bet that
    your ok with one battery.... based on the devices you describe.
    
    Another option is to put in a bigger battery (more amp hours) rather
    than a second batt.  Also, (maybe this was in orig note sorry if I
    missed it) if an outboard can you hand start it if the battery fails?
    If so, then your needs for an adequate size battery is less critical.
    
    Jeff

    you've certainly  asked a good question, Rick gave you a good answer,
    see if i can go a little furhter.
    
    1. what  is the  ampacity of your current battery. (not cold cranking
       amps) 
    
    2.  whats its age.
    
    3.what is the total amps per hr. that you will draw, if you ran all
      the devices you wish too.
    
        (some ratings may be in watts, needs amps per hr.)
    
    
    ex:  if the battery is rated at 100 amps, and the appliances you run
         will draw 5 amps per hr.  theoritically you could run them  for 
    
         20 hrs. but we both know that won't happen.
    
    
    here's another problem, your alternator may be rated at 40amps,
    but it won't generate 40 amps continuoulsy, when its charging
    it gets hot, and puts out less to avoid melting.
    
    soooooo, you could be playing a game of diminisheng returns,
    where-in each time you do this, you may not put enough back in
    to replace what you have used.
    
    its happened to me, in my case it took about 4 weeks to do it,
    i relied on my alternators to replenish them, and they couldn't.
    
    i would say in your case, that this will not happen.
    
    JIm.

    
    My father just bought a device called a BATTERY BUDDY (I believe).
    From what he tells me it is a device that will shut off the drain
    to the battery, by way of a circuit breaker, if the drain on the
    battery discharges it to a certain level.  It is designed such that
    there should be enough juice to re-start the engine.  He bought this
    because he has his depth sounder directly wired to the battery and
    has forgotten to turn it off a few times.  This device is designed to
    disconnect it if you have a drain on your battery that will discharge
    it past the point to be able to re-start.  I believe the cost is around
    $50 - $60.  He just got it I can try to find out how well it works.
    
    Mike

    Mike that battery buddy sounds good but also expensive, please let me know 
    any additional info.  I will try to get out to the boat tonight, find the 
    mannuals and get back to you with additional info.  
    
    The boat is an inboard with a Ford small block (351).
    
    Rick
    

RE: >>The boat is an inboard with a Ford small block (351).
    
Ah, ya should'a said that before!  Your alternator is probably good for a
minimum of 30-40 amps.  Combined with a top quality "27" series (large)
battery, you should have no problem unless you use the accessories for
several hours without running the engine.

You may want to just do a general electrical system checkover - make sure
everything's clean and tight, the battery's topped off etc.  Also, you
should use an ammeter to check the current draw of your accessories with 
the engine shut off.  Make sure none of the accessories are drawing anything
more than they're rated for.  Also make sure that with everything turned 
off you see no current draw at all, which would weaken the charge while 
the boat is parked.  

A dash mounted volt meter that reads in actual volts would also help avoid
any emergencies in the middle of the lake before they happen.  Once you find
out at what voltage the engine cranks slowly, you'll know enough to restart 
the engine before you reach that point.

Rick

    Here's the info guys;
    
    Alternator
    51 amp with  internal transistorized voltage regulator
    
    Battery
    360 amps cold crankingrating at 0F and 115 minutes reserve capacity
    rating at 80F 
    
    Accesories
    I have no idea what the draw on these are.
    
    Apelco VHS
    Uniden Cellular phone 
    Eagle Magma II fish finder
    
    Thanks 
    Rick
    

    We still need the AMPERE HOUR rating of the battery... not cold amps
    and reserve cap.  Those figures relate to engine starting only.
    
    You are operating low current draw devices.  The only time your
    cellular phone would draw significant power is when actually
    transmitting with it... the same with the VHF.  The rest of the
    time each device is drawing an amp or less.  With 4 devices on
    each drawing 1 amp you are using 4 amps per hour or 4 AH per hour.
    
    With a 40 amp hour batt which is a low average rating you can
    run '10' hours at that rate before the batt is dead.  Assuming
    you have an average 60 AH batt you can run 10 hours with no
    engine running with no resulting starting problem.  I still think
    you have no problem the way your set up... assuming the batt
    is in good shape.  It would be a good idea to recharge the batt
    once in a while with shore power charger... Also you can check
    the charge of the batt with a HYDROMETER which is the only reliable
    way to tell the charge state.  The voltage readings are tough to
    interpret unless the batt is VERY dead.
    
    Jeff

Actually, reserve capacity does not relate to engine starting. Reserve 
capacity is the length of time a certain current (usually 25 amps) can 
be taken from the battery before the battery voltage drops below a 
specified value (usually 10.5 volts, which is quite discharged). Many 
battery manufacturers no longer specify amp-hr capacity and only 
specify reserve capacity (sometimes for more than one load current).

A reserve capacity of 115 minutes probably implies that your battery
will supply 25 amperes for just less than 2 hours (when brand new)
before being effectively discharged. The battery will supply less
current for a longer period of time. The relationship isn't linear --
the battery will supply 5 amperes for somewhat longer than 5 times 115
minutes, where somewhat longer depends on the actually construction of
the battery. This non-linear relationship is why simply specifying
battery amp-hour capacity is misleading and inaccurate. 

A battery's capacity decreases with age. A new battery with a 115 
minute reserve capacity might have maybe only half that much toward the 
end of it's life. The only way to tell is to test the battery under 
load. 

The voltage of a lead-acid battery cell that has been sitting with no
charging or load current for a while (say 24 hours or longer) is quite
close to the specific gravity of the acid + 0.84. If you measure the 
battery voltage to the nearest 0.01 volt with an accurate digital 
voltmeter, you can quite accurately estimate the average specific 
gravity of the six cells in a 12 volt battery. True, this won't detect 
an individual weak cell.

While the load your electronics is placing on the battery is fairly low, 
I'd strongly suggest adding a second battery and a battery selector 
switch. Not very expensive insurance against all too common mishaps that 
result in a discharged battery unable to start the engine and/or a old 
battery with reduced capacity. 

    I am from the 'old school'.  I am used to amp hour ratings and the
    newer term reserve capacity I am not used to.  Thank you for the 
    info about it.  If the base noter can't find an amp hour rating
    but only reserve cap info then it sounds like that is the only
    info to go on.
    
    To the base noter:  There you have it... some recommending your
    ok the way you are... others saying you need two batts.  Your
    call now.  If you want to be extra safe put in the second batt.
    But if money is an issue and you pay attention to how much juice
    your batt has put out while your sitting I still think you can
    safely use just one battery.
    
    Jeff

    Ok, 115 minutes reserve cap.  Here is how I convert it to amp hours
    which means something to me.  25 amps x 1 hour = '25 amp hours'.  25
    amps x 2 hrs = 120 minutes which is close to 115 minutes.... 25 x 2
    hours = roughly 48 amp hours.
    
    Average size battery.  I still say what I have been maintaining ....
    that he is ok the way he is if he is careful about 'budgeting' his
    electrical load.
    
    Jeff

    Thanks for the help.
    
    I think I may have nothing to worry about.  What I'm going to do is
    take a volt meter reading now and seen where it is, then when I'm out 
    floating around with the diffrent devices on, take additional
    readings and watch the amps and how they drop.
    
    Thanks again
    
    Rick  

    IMO your BEST bet is an $ 8.00 hydrometer from an auto parts store.
    That instrument will give you an accurate reading of the the battery
    charge state with no fancy interpretation necessary.  I know, fancy
    interpretation is not really necessary.... but a hydrometer will
    give you IMO the most straightforward indication of charge state with
    the smallest chance of user error.  I am from the 'old school' I 
    grew up with batteries which actually had accessable intercell
    connectors, unscrewable vent caps, tar guck as a sealant and ampere
    hour ratings.  It was also possible via the intercell straps to
    do high amperage current tests cell by cell to find dead cells.
    Now batteries are the high tech plastic sealed boxes which tend to
    be 'good or bad' with no repair possible.
    
    Jeff

    
    I have an outboard with a (groan) 9A alternator so this is a big issue
    for me, but I've found that  small boat electronics (DF/FF, VHF (mainly
    receiving), Loran) use very little juice.  Your running lights will be
    more of an issue if you plan to go out at night.  Watch out for those
    10 zillion candlepower spotlights.  They use huge amounts of current
    (12-20A).
    
    However, if I did a lot of night boating or spent long amounts of time
    at idle (or worse, stopped), or added any other gadgets, I would be in
    trouble.  I do have two batteries, but that's just a safety measure
    (moored boat, charged battery always available to start engine even if
    I forget to shut something off).

    My boat has NO alt on the outboard.  I use a 50 AH batt for fish finder
    engine starting, bilge pump, and running lights.  I can go for WEEKS
    without needing a recharge during summer weekend only use.  Thats why
    a couple of hours with less than my load on the original noters boat
    does not impress me as to being a safety problem.
    
    Jeff

RE: Note .73 
>> Thats why a couple of hours with less than my load on the original 
>> noters boat does not impress me as to being a safety problem.

Well, it *is* somewhat more of a safety problem in Rick R.'s boat than
your's Jeff.  If your battery goes dead, you can always yank on the
starter rope and start your 2 cylinder outboard.  Kind'a tough to do
with a 351 V8, even if you could find a place to wrap a starter rope
around.    8^)

Rick

    Yup, right Rick.  I did agree that two batts would be safer than one.
    BUT, if one pays attention to amps delivered by the batt, and has a
    budget to follow, I believe one batt can do the job safely.
    
    For many years I have used a truck camper.  I have run it with single
    and dual batt.  Often the battery or batteries have to carry the 
    load for two nights and two days with no engine running.  I agree its
    not the same if a dead batt wont' start a land vehicle. My point is
    that over the years I have developed a 'feel' for what one can do
    with both one and two batteries.  I NEVER had a starting failure on
    a single batt system due to overuse in the truck camper.  His 
    application is less rigorous electrically but with safety consequences
    I didn't face.  Thats why I still maintain he can safely, yes safely
    use just one batt IF he has a battery in good shape.  Checks its
    charge state at home occasionally with a hydrometer and pays attention
    when on the water to its use with the engine off.
    
    A dolt who pays no attention to battery charge, or electical use IS
    setting himself up for a no start condition on the water.
    
    Jeff

    re .74
    
    I have a Johnson 115 and it comes with a rope to start it in case of
    battery failure.  Well I consider myself of above average strength
    and there is no way I could pull the rope hard enough to even think
    about starting the engine (assuming I was not doing something wrong).
    It was the time I fried this so called emergency method that I decided
    that 2 batteries was a much better idea.
    

    RE: .76
    Right, I agree, you can't rope start your 115.  My Johnson 88hp
    also came with a rope under the hood, but it's a joke.  I was
    referring though to Jeff's boat, which only has a 40hp and a
    recoil starter.
    
    Rick

    Actually Rick, my boat has a 25 HP with electric start. I CAN pull 
    start it but don't bother usually. 
    
    Jeff

Rick,
	To answer your original question, sounds like you enough capacity 
to run your equipment for a reasonable amount of time. You also implied 
your concern was about being stranded in the "middle of the lake". This 
implies to me that you are not in immediate danger should your battery fail.
This of course depends on the lake your talking about. I'm assuming something 
smaller than the great lakes with a fairly high population of nearby boaters.
	With the above assumptions, you could rationalize one battery. I use 
a livewell and raw water pump as well as the usual electronics (sparingly of
course) and don't have a problem with discharged batteries. I however prefer 
two; not just for power considerations but safety as well. A healthy battery 
can go South fast if a short develops somewhere. Also, if your motor becomes
difficult to start the reserved capacity of a second battery may help. 
	My boating is done offshore without many nearby boaters and this 
probably influences my thinking but I like to know there's a fresh battery 
ready to start my motor when I'm ready to head ashore. I even have a charging 
system on my auxiliary motor so that I could charge up a battery or at least 
run the radio and running lights on the way in if all else fails.
	To sum it up; you could go with one electrically and probably safely
too but if you want piece of mind invest in a second. 
Paul

re .79:

I agree. The ocean has been quite accurately described as the most 
immediately hostile environment on Earth. In my view this comment
also applies to any body of water large enough to float a boat. Some 
friends of mine who have spent the last five years living aboard
cruising the East Coast have said that the more time they spend afloat,
the more dangerous they think the ocean is. Depending on a single
battery is taking a greater risk than I would be comfortable with (my
boat has three). 

    Moved by moderator
    ------------------
    
              <<< VICKI::SIE$DATA0:[NOTES$LIBRARY]BOATS.NOTE;1 >>>
                                -< Powerboats >-
================================================================================
Note 971.0                      Battery Discharge                      2 replies
SALEM::GILMAN                                        55 lines  29-APR-1992 07:26
--------------------------------------------------------------------------------
    Moderator: I can't find the orginal note which had the discussion
    about the advisability of a single or dual battery installation for
    a boater who had questions about it.  Please move this note as 
    appropriate.
    
    The boater wanted a cut off voltage to tell him when he had a dead
    battery.  I looked the following info up in STORAGE BATTERIES by
    George Vinal (Physicist Nat. Bureau of Standards)  John Wiley +
    Sons publisher.  
    
    Also, I worked at Anderson Power Products at an Eng. Dev. Lab.
    in the late 1970's.  Our job in the lab was to develop a 'fuel
    gauge' style meter (voltmeter) which could tell the user what
    their batt charge state was.  We ran tests for months and eventually
    came out with a meter which did the job.  BUT.... a simple voltmeter
    WILL NOT DO THE JOB regardless of whether its a DVM to 4 or five
    places right of the decimal.  BECAUSE there are too many variables.
    One needs an 'integrating voltmeter' which is designed for lead
    acid batteries which internally averages out the readings.  My
    suggestion to the noter is if he wants to use a volt meter rather than
    a HYDROMETER to BUY A COMMERCIAL METER THRU A MARINE DEALER which
    is designed to be a 'fuel gauge' type of battery charge indicator.
    
    A typical auto/marine battery is typically characterized by discharging
    it at a 20 hour discharge rate.  That is it takes 20 hours to run it
    from full to discharged state.  One divides the amp hours by the time
    (example 50 AH divided by 20 hrs = 2.5 amps discharge rate).  
    The six hour discharge rate for a 50 AH battery would require a 
    current of approx 8 amps.  
    
    The book gives a cut off voltage of 1.75 volts per cell or 10.5 volts
    for a 12 volt battery as the discharged cut off voltage for a battery.
    BUT that cut off voltage will vary some according to the instantaneous
    discharge current.  If running ones discharge by the book... six or 20
    or discharge rate one can use the 1.75 volts per cell and be sure its
    right. In a typical boat the load varies and the cut off voltage will
    still be 1.75 volts per cell BUT the voltage will 'bounce' around 
    with the load or NO LOAD when taking the reading.  My point is that
    for practical purposes a guy with a DVM crouched in the bilges is 
    going to be GUESSING at his average load etc.   
    
    After curring through all the above I suggest EITHER BUY A HYDROMETER
    AS I SAID LAST WEEK.  1.260 is full charge Sp grav.  1.220 sp grav.
    is cut off discharged point, or BUY THE COMMERCIAL FUEL GAUGE STYLE
    battery meter.
    
    I suggest not running the battery down more than 50 % with the engine
    off to insure a reliable start.  Whats the 50 % voltage?  DEPENDS ON
    DISCHARGE CURRENT..  Whats the discharge current your going to use?
    See what I mean.. can't call it.
    
    Got to get to work.. will answer later to anymore questions.
    
    Jeff
    

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              <<< VICKI::SIE$DATA0:[NOTES$LIBRARY]BOATS.NOTE;1 >>>
                                -< Powerboats >-
================================================================================
Note 971.1                      Battery Discharge                         1 of 2
UNIFIX::BERENS "Alan Berens"                          9 lines  29-APR-1992 08:25
                               -< too expensive >-
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re -.1:

True, an integrating device to measure the total ampere-hours used is 
probably the most accurate way to determine how much of the battery's 
capacity has been used. Unfortunately ....... cost. Ample Power sells an 
excellent digital voltmeter/ampere-hours used system. $299 list. It 
would be much cheaper to buy a second battery. More reliable and safer, 
too.

    
    Moved by moderator
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              <<< VICKI::SIE$DATA0:[NOTES$LIBRARY]BOATS.NOTE;1 >>>
                                -< Powerboats >-
================================================================================
Note 971.2                      Battery Discharge                         2 of 2
SALEM::GILMAN                                         9 lines  29-APR-1992 09:25
                                   -< Agree >-
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    Yup, I agree. But he asked for the cut off voltage.  It took quite
    a bit of hunting thru the batt book to come up with a safe number
    which took into consideration the variations of different applications.
    
    The number I am comforable with (for my use too) is 1.75 volts per
    cell for total discharge.  
    
    
    Jeff

    Dumb question time.   How are the batteries hooked up in a twin
    engine boat?   There must be two alternators, right?   And usually at
    least two batteries (and I've seen 3-4).   That's a lot of permutations
    of possible combinations.  Or are the alternator outputs simply
    paralleled and the problem reduces to the same as multiple batteries
    with one engine.   
    

    
    With smoke and mirrors.
    
    All kidding aside, lets say there are 4 batteries. 
    
    2 are connected to one engine, and 2 to the other. 
    
    the alternators don't see each other.
    
    in an emergency there is usually a crossover in the event
    on engines batteries won't start the engine.
    
    simple, right??
    
    JIm.

    Well that ceratinly seems simple and logical for starting, but with
    two separate banks of batteries, which ones provide DC power for the
    rest of the boat?  Or do you switch back and forth to level the loa?
    

    
    there not all the same, its not an easy question to answer.
    
    JIm.
    
    
    

    The 1 alt. 2 battery set up will work with a 2 position guest switch
    but unless the output of your alt. is greater then 100 amps DON"T put
    the switch in the both position.The alternate setup is to get what they
    call is a isolation diode that keeps the 2 batteries from discharging
    into each other and allows the standard size alt.to charge both
    batteries at the same time without overloading the alt.Both are
    available threw most marine supply or auto supply.The auto version
    maybe cheaper but it should be ign. protected for saftey.
    
    

    
      Why can't one place the battery switch in the 'both' position if the
    alternator is less than 100 amps?
    
    				Kenny

re .last:

You can. The alternator output will go to both batteries with the more 
discharged battery getting a larger charging current. Very rare is an 
OEM alternator with more than a 50A output. We used a single 45A (cold, 
more like 30A max under most conditions) charging two batteries in 
parallel for years. Worked well enough. There are several detailed 
discussions of sophisticated battery charging systems in the Sailing 
Notesconference.

Alan

    Because if your batteries want more then the alt. can deliver for a
    long period of time you will burnout the alt..Most of the time if the
    batteries are not to low you will beable to get away with it but who
    knows when that low point is reached and when it is you will cook it.
     I know because I thought the reg. would take care of the alt by not
    allowing it to chargeover its capacity guess what $130 dollars latter
    I know better.

re .91:

I think you misunderstand what an isolator does. An isolator is simply 
two or more diodes through which the alternator charges the batteries. 
The function of the diodes is allow all batteries to be charged 
regardless of the position of the battery switch. The isolator, per se,
does nothing at all to limit the alternator output current. If for some
reason a battery is accepting a very high charging current (eg, the
battery has a defective cell), the alternator may well be destroyed by
overheating, isolator or not. 

Isolators have a serious side effect -- the alternator regulator usually 
senses output voltage at the alternator output. There is about a 0.7 
volt drop across the isolator diodes, so that the actual battery 
charging voltage is 0.7 volts less than it should be (this, by the way, 
does reduce the charging current, which does tend to reduce the 
probability of alternator damage due to excessive current). But, the 
batteries will be chronically undercharged and the time to achieve 
nearly full charge will be very long (hours perhaps). Undercharging 
significantly reduces battery life.

Alan

re last couple

	There is a point at which a battery becomes discharged enough that its
internal resistance rises   *_A LOT_*.  If you've ever left your car headlights
on, say overnight, you may have noticed that the battery will only accept a very
small charge at first.  So, I guess the answer to the question about alternator
overloading might depend on how far each battery is discharged as well as how 
many batteries are being re-charged.

	Reg	{not a mention of fees or taxes (-: }

re .93

	Sorry 'bout that, I seem to have confused recharge (battery context)
with charge (fees, taxes, etc.).   To clarify;  "Recharge"  in the context
of the last few replies in this string, is about converting electrical energy
into   .....mumble, chemical something mumble,.... so that it can later be 
retrieved and converted back to electrical energy for .... various uses, such as
starting engines, running lights, refridgerators, etc.

	In the context of some other replies in other strings  "recharge"  seems
to refer to recurring fees, taxes, etc., i.e. annual fees  {errr, "annual" ??}
In those replies  "charge"  refers to single time fees, taxes, etc., such as 
title, sales tax, and other opportunities to contribute to the general fund
that supports all the social programmes that we're all in favor of.... right ?
right.

	Reg
 

    Moved by moderator.
    
================================================================================
Note 1029.0        Should batteries be charged before storing?        No replies
ICS::SOBECKY "It's all ones and zeroes"              11 lines  13-NOV-1992 12:09
--------------------------------------------------------------------------------
    
    	I've taken my Sears Die-Hard battery out of the boat and will
    	store it for the winter. Question: should I give it a good
    	charge before I store it away, or should I wait till the spring-
    	time, or doesn't it matter one way or the other?
    	
    	BTW, the battery is 2 years old. Didn't give me a bit of trouble
    	this past summer; I only charged it once at the beginning of the
    	season.
    
    	John

    Charge it up, if you read the other replys they will say why.
    
    Gordon

    Charge it.  I even recharge mine in about March (probably overkill but
    if you use an automatic charger which shuts off when fully charged, it
    won't hurt the battery).  Also, a battery left on a concrete floor will
    slowly discharge itself.  Leave it on a piece of wood off the floor.
    Wayne

A recent article in Boating magazine on winterizing 
electronics claims that the notion that batteries
shouldn't be stored on a concrete floor is an old wives'
tale.

I realize that this mag is hardly a paragon of all forms
of boating knowledge, but there is at least one 
dissenting opinion.  (This guy also said to take the
batteries out of the boat, and we've heard differing
opinions on this too).

    Definitely charge it now. Leaving it discharged will increase the
    damage done to it. (All use causes some damage.) Having not charged it
    all season is not the best way to treat it - keeping it fully
    charged is the best way. I too have had no charge put into my
    new-this year Die Hard for most of the season. It is on a slow charge
    right now. 
    
    There is plenty of information on charging batteries either here or in
    sailing notes, if you are interested in the details of how to best care
    for your battery. There are also books written with chapters on the
    subject. The biggest think is to recharge it now, and again in the s
    spring. Topping it off each month or two this winter would be even 
    better.
    
    Bill
    

    Charge it BEFORE you store it and top off the 'water' now as you want
    it mixed in by the charging gases.  If you let it go the normal lead
    sulfate which was formed upon discharge will harden up and will not convert
    back to lead dioxide and lead perxide in the Spring.  I agree with
    another charge it now and then again just before you put it in the
    boat.  Depending on the storage temp you may or may not need to charge
    the battery periodically during the winter.  If at temps below about
    50 F don't bother to charge it during the Winter after your Fall lay
    up charge it will hold the charge at lower temps well.  If its in a
    heated basement 70 deg or so charge it up every six weeks.  If you
    DON'T charge it up because its at cold temps you DON'T want to add
    water during lay up as it may freeze.  Also, it won't need any more
    water if it isn't getting charged periodically during the Winter.
    
    I second the input on the concrete floor storage being an old wives
    tale.  My source of information is the Production Manager of Surrette
    Battery Co. of Tilton, N.H. 
    
    Your more likely to discharge your batt during a layup by leaving the
    top of the battery filthy, currents will leak over a period of time
    through the crud.
    
    Jeff
    

    You can test the crud-on-the-top theory with a relatively sensitive
    VOM.  Just touch a post and anywhere on the top or sides of the
    battery.

    Why not just clean it off, and not bother with testing...
    
    JIm.

    I said you can test the THEORY by testing the battery...

    
    	I "wonder" if the story around batteries on concrete floors
    	discharging has anything at all with the fact that concrete 
    	dust is a base ? and perhaps it's really concrete dust and
    	battery acid, not the fact that the battery is siiting on the 
    	concrete floor ?
    
    	I now return you to your regularly scheduled program
    
    	
    	

    As I was winterizing my 5hp Merc outboard this weekend, I dusted off
    and (re-)read the owners manual and maintenance manual. The maintenance
    manual specifically stated NOT to store batteries on a concrete floor.
    
    I have heard it postulated that a concrete floor acts as a heat sink,
    causing temperature gradients to be set up in the battery which result
    in some internal discharge. This is the only explanation that this
    (electrical engineer - by education) sailor has heard that might be a 
    plausible explanation of why to avoid concrete.
    
    Bill
    

    The production manager of Surrette Battery Co, in Tilton, N.H.
    maintains that the concrete floor discharge issue is an Old Wives
    Tale and it is simply not true that batteries stored on concrete
    self-discharge faster than batteries stored on other surfaces.
    
    Jeff

    I believe I've got a faulty regulator as it's not putting out 14+ volts
    as some literature I read says it should. The alternator is a 1977
    vintage Prestolite.
    
    Can anyone tell me where to look for the regulator (I'm assuming it's
    external). I see a small oval casing mounted to the rear of the
    alternator with 2 studs. Could this be it?

    It probably depends what type of regulator/engine you have. On my 1973
    I just replaced a bad regulator. It was mounted on the front of the
    thermostat housing.
    
    You may want to follow the wire on the alternator from the field
    terminal back to the regulator. regulator is probably a small metal
    enclosure about 2" x 3" with three wires.
    
    Make sure the regulator has a good ground, won't regulate properly if
    the ground is bad.
    
    The small oval casing is probably an alternator fuse of circuit breaker
    also a good place to troubleshoot.
    
    
    Mike
    

    Ok, I think you are correct. I looked closely and it's stamped
    Prestolite iwth a number of "VSH 6201". Looks just like you describe.
    
    How did you know your regulator was bad? Did it just stop working
    altogether? In my case, meter on dash (most of the time) shows a slight
    charge (amps). Other times, it will show a slight discharge. This
    happens purely at random. What I know for sure is that the batteries
    gradually lose charge.

    My sympton was first a blown fuse replaced with a circuit breaker.
    
    Then came a constant 30-40 Amp charge on the battery.
    
    Went to a local motor repair place and talked to the experts. They
    checked out the alternator and it was fine. Said that if the regulator
    goes bad it will 1) cause a constant charge since one of the internal
    transistors shorts out putting full 12v on the field or 2) will not
    charge at all if transistor opens.
    
    Cost of new regulator was 26.00 vs 190.00 for an alternator.
    
    I'm a happy boater.
    
    Mike
    
    

    
      Al, intermittent operation of your alternator like that is often
    caused by worn out field brushes. When they get worn out, they have poor
    contact, sometimes working and sometimes not. They're pretty easy to
    replace if your alternator is not too corroded. Solid state regulators
    usually either work or don't work (all the time). So you'll want to
    check them too.
    
    				Kenny

    You might also have one or two diodes gone on the alternator, symptoms
    would be no more than, say, 10 or 15 amps charge, with no load (lights,
    etc.) and discharge under load.  
    
    If you elect to replace the brushes, you might as well take the
    alternator to the place in Windham? Pelham? that specializes in
    rebuilding alternators and starters (can't remember the name).  They'll
    rebuild your alternator for less than 50 bux, typically, replacing the
    bearings, checking the diodes, etc.
    
    I've had regulators that cause the voltage to pulsate, making the
    lights flicker, not sure if they were transistorized, tho.
    
    Carl
    
    

    I think I'll go for the alternator rebuild (locally in Maryland, not
    MA). In the course of all of this, it appears that my solenoid has gone
    amuck as well.

    Greetings!  I have some general "first time" recharge ?s...
    
    I have 2 boats and 2 Sears Marine batteries currently stored in my
    basement on the concrete floor but within their repsective plastic
    marine battery containers.
    
    Does it matter if I leave these on the floor or should I definately 
    stick some wood under'm?
    
    Both batteries read 12 volts, and their inidicators are green.  Should
    I charge them up anyways?  
    
    I understand it is good practice to charge before storage and then 
    again in the spring coming out of storage.  True?
    
    There batteries were never "recharged" during the last boating season.
    
    What is the correct charging procedure.  I am borrowing a 6/2 amp Sears
    charger.  The charger specs say to use 6 amp for large auto/marine
    batteries, and 2 amp for smaller vehicle batteries like lawn tractors.
    I really wanted to do a "trickle" charge, would that be 6 amp?  
    
    Do I remove the battery cell covers while charging?  How do I know when
    the charging is completed?
    
    Much thanks, Mark
    

    
    its very simple, check the water level, add if necessary, 
    in either case charge them up, when your charger reads 1 or 2
    amps, thats enough.
    
    the next easy step, leave them alone until spring, put a charge on
    them again, reading should be the same, and put them i the boat
    the alternator will do the rest.
    
    there is no need to overdue the battery put away task.
    
    just leave them alone, they'll be fine.
    
    JIm

    You might not want to charge them in your cellar, due to the hydrogen
    gas that can be produced by the charging process; the gas has no place
    to go, except maybe your furnace (boom!).
    
    Carl

    Leaving the batteries on concrete will NOT cause them to discharge.
    That is an old wives tail.  (My information source is the production
    manager of Surrette Battery Corp.)  The batteries slowly discharge due
    to 'local action' on the plates due to unavoidable impurities in the
    batteries.  But the RATE of self-discharge is TEMPERATURE dependant.
    Below 40 deg. F the self-discharge rate is virtually non existant.
    (Source of information: The same, Surrette Battery Corp.)  At 70 deg.
    F or above you should recharge the batteries once a month while in
    storage.  If your storing the batteries at outdoor temperatures in New
    England a Fall charge with no winter boost is fine since temps are low.
    
    I would NOT leave the batteries on an extended trickle charge... the
    positive plates will be destroyed over a period of time.
    
    I would boost the batteries in the Fall until the charge rate dropped
    to zero amps or virtually zero amps.  If the battery was still charging
    at 1 amp I would wait overnight and see if it fell off to zero amps.
    If it stays at 1 amp or more after at least a 12 hour charge I would
    agree with the prior noter... stop the charge and store the battery. 
    But if its about 1 amp after only several hours of charge you can't be
    sure the battery is topped right up.  You won't hurt the batteries with
    an 'inapproprate' OVERNIGHT 1 or 2 amp charge because the charger
    voltage is not adjusted just right, or because your line voltage is a
    hair high causing the charger to deliver a slight charge even though
    the battery is right up to full charge.
    
    (Of course you can use a hydrometer or digital voltmeter to check out
    the charge state.)
    
    What ever you do DON'T store the batteries in a partially discharged
    state.... that will ruin or even freeze them if the temp goes way down
    because the electrolyite can freeze in a discharged battery because the
    S04  (H2 S04, SULFURIC ACID) will be tied up as sulfate on the plates
    and the electrolyte will be largely water.  BUT
    in a CHARGED battery thats not a issue because the S04 is mostly in the
    acid which will prevent freezing.
    
    A fully charged battery won't freeze until you get down around - 40 F
    or lower.
    
    Jeff

    Oh yeah... the vent caps.  Leave them ON, they are designed to trap and
    recondense evaporating electrolyte mist.... also you don't want
    sulfuric acid mist all over the battery top, connectors, and anything
    else nearby.  That is, leave them on except when checking electroyte
    level.
    
    Unless your battery is gassing alot I wouldn't think you need to do
    it outdoors as long as your cellar is reasonably well ventilated.
    
    Jeff
    

    Well here is what I did over the weekend to battery number 1.
    
    In cellar with windows open, removed caps, set charger to 6 amps and
    let run.  The charger came down to a 6 amp reading within about 30
    minutes.  Then about 8-10 hours later was down to about 4 amps.  Shut
    charger off, and started again the next day.  About 8 hours later the
    reading was down to about 2.5 to 3 amps.  Took an analog meter to the
    battery (with the charger disconnected) and read about 12.5v.
    
    I was waiting for the reading to go down to 1 amp, but it was not
    happening (or perhaps I did not wait long enough).
    
    I never smelled any odors (does the gas produced have an odor?).
    
    Also the cell water levels always remained at the full mark.
    
    I figured this battery is done.  Am I right or wrong here?
    
    Battery # 2 has not been charged yet.  I will hookup but ensure caps
    are left on while charging.
    
    Thanks, Mark   

    The battery is not done. Take a voltage reading with the battery
    charging... let me know what it is.  Gassing (or the lack of gassing)
    is an excellent indicator as to whether the battery is accepting the
    charge.  Lack of gassing (or minor gassing) means KEEP CHARGING because
    the battery is utilizing the current rather than 'blowing it off' by
    gassing.  At 2 amps with a virtually fully charged battery you should
    have very noticiable gassing.  I would put it back on charge for
    another 8 hours and see if it drops further.
    
    SOMETIMES a damaged battery will simply keep 'accepting' the higher
    charge rate (4 amps or so) without utilizing it... but the battery
    will generally gas pretty vigorously too.  Do you have a hydrometer?
    They are cheap at an auto parts store... $ 10.00 or so. It will tell
    you ALOT about the battery.  I suggest you buy one and give me the
    readings.  A fully charged battery (after an overnight sit) with
    no charging should read about 1.260 to 1.265.  You must let the battery
    sit to get an accurate reading since the electrolyite will be full of
    gas bubbles right after charging and will give a false reading.
    
    Remember, no sparks around the cell tops of a charging battery. Also
    the vent caps should be ON while your charging it.
    
    Jeff

    Jeff,
    
    I'll pickup a hydrometer and get back to you later this week.
    
    Thanks, Mark

    Greetings!
    
    I picked up a charger at a yard sale last weekend.  It is supposedly
    a marine grade charger.  I was wondering if anyone ever heard of this
    charger.  I tried calling the manufacturer for an owners manual and
    perhaps a spec sheet/schematics for the unit, but the 800 number was
    no longer in service.
    
    The brand is "QuickCharge" and the model is "Fisherman Charger", the
    unit # is QPTR12V/25A.  It is a 25 amp charger, electronically
    controlled and I am told it can fast charge or trickle charge and will
    supposedly correct its charging state so as to not destroy a battery.
    It may even shut itself off.  But, I am really not sure of its
    operation which is why I was wondering if anyone was familiar with this
    unit and could tell me more about it.
    
    Thanks, Mark