Re: (ET) Lessons learned: batteries and diodes

[Jeremy Gagliardi com]

It is true, there are fairly good modern chargers out there.  However,
some are not.  The "modern" chargers I bought, which said they could
handle "deep-cycle" batteries, never got the voltage above 6.5 per
battery.  You need to get a voltage of 7.5/batt finish charge, I'm told
by others on the list, then it will taper down to 6.5V after the charger
is off.

The charger I had was 10 amps, but on "auto" mode, the cycle ended
withint 2 to 3 hours, which was not nearly enough to fully charge the
batts.  It only took the batteries up to 6.5V finish charge, which then
tapered down to about 6V after the chargers went off.  That is
insufficient.

It is also true that the GE charger can overcharge certain batteries as
it tries to equalize them.  Whatever batteries were drained the least,
will get overcharged.  In that light, it might be a good idea to use a
single 12V/10Amp charger to charge the pair of batteries that is drained
the most, then when they are about up to what the other batteries are,
turn on the GE charger.

-- 
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 mailto:Jeremy Gagliardi com
 http://Jeremy.Gagliardi.com/
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"David Roden (Akron OH USA)" wrote:
> 
> On 29 Oct 2001, at 10:44, Jeremy Gagliardi com wrote:
> 
> > The small, 12V, car or boat battery chargers are not really sufficient 
> > for
> > these large, deep-cycle batteries.
> 
> It sounds like your 12-volt chargers were cutting off too early, before
> the voltage reached 2.4 to 2.45 volts per cell.  If true, that's not
> adequate for any lead battery, deep cycle or otherwise.  The dealer
> should give you a refund on them.
> 
> It's true that low-current chargers (6 amps or so) will take a good while
> to charge up a 220 amp hour battery (appreciably more than 36 hours from
> 100% DOD because the charge tapers).  But that's not much of a problem
> for a machine that's seldom used more than once a week.
> 
> Your experience notwithstanding, I stick by my recommendation.  A set of
> three 12-volt chargers (or six 6-volt) will charge more effectively and
> make your pack last longer, as long as they have a reasonably good charge
> algorithm.
> 
> My 10-amp Exide chargers have a so-so algorithm; they are basically taper
> chargers with a "cycle-dropping" controller, that is the type that cycles
> the charger on and off at intervals of a second or so to control finish
> voltage.  They push my gel cells up to 14.3 volts (on-charge voltage),
> which is about what the battery manufacturer recommends.  They've worked
> just fine for me for about 2 years now.  I wouldn't hesitate to use them
> with flooded golf car batteries, though I might turn the voltage limit up
> a bit.
> 
> The GE charger's control is fairly crude, and it appears to me that it
> mostly overcharges.  Some people think that overcharging is better than
> undercharging.  They're both bad for batteries.
> 
> But again, the ET is typically run once a week at most, so even if cycle
> life is dropped from the ideal of 700 or so cycles (for golf car
> batteries under optimum conditions) to 300 or 350 cycles, you still get 
> 6-
> 7 years of life from the pack.
> 
> David Roden - Akron, Ohio, USA
> 1991 Solectria Force 144vac
> 1991 Ford Escort Green/EV 128vdc
> 1979 General Engines ElectroPed 24vdc
> 1970 GE Elec-trak E15 36vdc
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