Re: Equalizing... How many amps do I need??

["Chuck Hursch" <chursch@yahoo.com>]

evblazer@softhome.net wrote at Friday, March 29, 2002 7:05 AM:
>
> Warning: First battery pack so I have no idea what i'm talking
about :-) I
> have 15 US and 4 Dynos.. (dynos have about 20 less cyles of
them)
>
> I'm trying to find a charger to peek up some individual cells
and equalize
> them which kind of brings me back to my "bulk" charger. I don't
think my
> current charger which only puts out ~1 amp at 180 volts which
is like 2.36
> per cell equalizes. I'll probably pull the worst battery and go
down to 144
> which would at least be 2.5 volts per a cell but i'll still
only have ~1
> amp at finish, it drops under 2 amps at about 170 volts..
Voltage and
> Current knobs are on max..
>
> The batteries don't bubble or gurgle and they don't need water
after almost
> a whole year of driving them, okay only 4000 miles but it's in
a blazer. So
> is 1 amp enough? if so is 800ma.. reason I ask is I found a 10
volt 800ma
> power supply that I could hook up to peak up the individual
batteries
> maybe. I've probably trashed my batteries but i'd like a few
more months
> out of them before I have to get a new pack, and new PFC-20
charger. I'm
> down from ~30 miles to ~13 miles which can't even get me to the
train
> station and back, mid winter I was doing the 18 miles with some
room so
> spare. Any help would be most appreciated, please be kind :-)

My impression is that an "equalize" charge is C/20 or C/28 (where
C is the capacity of the battery in amp-hours - say 235 A-hr for
a US125 6V'er), so this implies about 8-11A.  Also, no voltage
limit.  I believe it was Nawaz at US Battery that recommend C/20
and the no-voltage limit (see the archives).  So what I do is
give my relatively new (1-year) Trojan T-125s (same capacity as
the US125) a 2-hr equalization once a month.  The amazing thing
is the voltage that these batteries go to:  about 8.25V-8.50V
per.  My old pack (US2300s - old version of the US125) never did
that, although when it was new I didn't have a variac to drive
the batteries this hard.  I'd hate to think what these batteries
would go to if I did 11A - ouch (8.75V??).  One thing that
worries me though is that frequently it seems the batteries take
awhile after that (2 or 3 cycles, or maybe quite never) before
they'll come in on a normal charge with as low a current for a
given voltage as they did before the equalization charge.  I hope
I'm not trashing them!
>
> Mark Hastings
> '83 S-10 EV Blazer (suffering from chronic undercharging)
> www.geocities.com/evblazer

Chuck Hursch
Larkspur, CA


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