Todd chargers... again [RE-wrenches]

[Backwoods Solar Electric Systems]

Actually you can gain charge rate by paralleling chargers.  The increase in
charge rate will raise the battery voltage somewhat, and if that gets close
to the cut-off voltage your output from each charger will be cut back.
However, you still gain in total rate if the battery bank is large enough
and discharged enough to accept the higher rate.  Example:  We run a 12 volt
bank of 12 Trojan L-16HC batteries, rated capacity 2370 amp hours.  A trace
SW2512 charges about 100 amps, for a C/20 rate.  To increase the rate in our
sunless winters I added two Statpower Truecharge 40+ which each contribute
their rated 40 amps for a total charge very close to 180 amps (C/13). These
are driven by a 10 kilowatt Kohler generator.

While I have seen some surplus telephone chargers oscillate and swap rates
with Trace U series inverters and Todd chargers, the combination described
above is completely stable.

Steve Willey   www.backwoodssolar.com
Backwoods Solar Electric Systems

----- Original Message -----
From: Todd Cory <toddcory at jps.net>
> I don't want to whip a dead horse, but went to look at a job today and
they had 2, 75 amp Todd chargers in series feeding a 1250 AH bank of Trojan
T 105's. The inverter is a trace mod sine wave with charger (SB option), so
this makes little sense as when chargers are added like this in parallel, it
seems the more of them you add, the less you get out of each one. The small
voltage boosting transformers in series with the generator are much more
effective at increasing charging output from mod sine wave inverters and the
price is less also. The question I have is: does series-ing 2, 75 amp
switching chargers like these Todd's work? It seems to me that Richard said
he had tried this and had marginal results.
>
> Here's a new one I've never seen before... the system above has 16
identical Kyocera J51 panels... as they are 12 volts each they need to be in
series to get 24 volts out. Generally I connect a bunch of individually
series 24 volt strings into parallel to feed the load... this installer
paralleled 2 sets of 8, 12 volt panels together and then series these to get
24 volts... probably the same result, but I know there is some reason this
is not done when combining batteries for higher voltage, and I wonder if the
same reasoning holds for PV combinations as well.  Anyone got any info on
this wiring style, or pro's or con's for each variation?
>
> Thanks,
>
> TC
> --
> Todd Cory
> KE6SXS
> toddcory at jps.net
> Bald Mountain Solar
> P.O. Box 689
> Mt. Shasta, Ca. 96067
> (530) 926-1079
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