Geoff Schultz wrote in
:

I note that my batteries (2 Caterpillar 153-5720 8Ds) are speced at a
max charging rate of 5% of their CCA, which is 1500 A. That works out
to 75 A. Each of the batteries have a rating of 210 AH, which based
upon Larry's math, would be 21 Amps, or 42A for both of them.

That said, this whole discussion doesn't make a lot of sense to me. I
watch my 3 stage regulator charging rates, and it spends very little
time charging at full throttle. When initially turned on, the charger
goes into bulk charging mode and attempts to get the charging voltage
up to the bulk charging voltage. This voltage depends upon the
battery temperature and I have a thermocouple which sends the battery
temperature back to the charger. I've specified a temperature
coefficient in the charger (which is specified in mV/degree C) and as
the battery gets warmer, the bulk charging voltage drops.



The 3-stage charger bulk charges the initial load of electrolyte between
the plates that WILL take a tremendous current and charge with it until
it has been converted back to acid and replated the lead. Then, as you
say, it drops back to give the battery time to recover its electrolyte by
convection back between the plates with a much lower charge current
(stage 2) after the voltage rises from the recharge I alluded to in stage
1. State 2, a more sedate charge rate that prevents you from warping the
plates with 100+ amps by melting them, possibly causing a
short/explosion, continues unabated with short periods of zero current
for charge testing, then turns back on until the test period voltage
remains higher than the natural voltage of the cells, indicating nearly
full charge. It then switches to stage 3 which is a very slow topping
off charge.

Investigating Lew's 115A at 14V massive charge for 3 hours shows 115 X
14V = 1,610 watts being shoved into the battery. At first, this will be
absorbed a lot by the chemical reaction converting back to acid. But, as
the charge between the plates quickly completes and he goes into the
gassing phase converting his water into hydrogen, this power starts being
turned into heat, heating the electrolyte and plates, which are soft to
begin with, an possibly, probably, warping the plate structure,
especially if the cells aren't straight up vertical, such as being heeled
over with sail aloft of sloshing about in the waves. 1,610 watts is a
lot of DC power to pour through a rubber or plastic case...and will not
just go off easily sealed away in those tight battery boxes that insulate
the battery from any air cooling....making the heating problem worse.

He didn't want to hear my sad story, so I hope the rest of you will think
about what I'm saying before the big bang coats your boat with
acid....not a pretty sight at all!

Larry
--
Cursing me won't change physics or chemistry.....