Larry wrote in
:

Lew Hodgett wrote in
news:1QTpi.12042$zA4.313 @newsread3.news.pas.earthlink.net:

To replace 375 AH you will require 375/115 = 3.3 hours of engine
time.



A pipe dream of battery chemistry. 375AH requires 5 hours (from 50%
discharge, not zero) at 38A, not 115. Batteries charge at 10% of AH
rating, not 30, if you want to convert the electrolyte, giving it time
for circulation.

The two batteries will recharge from 50% very nicely at moderate
temperature at 75A for 5 hours on the new 90A alternator. NO battery
will charge at 115A for very long before the interplate electrolyte
has been converted faster than it can be replaced by convection in the
electrolyte. This is why you see the current drop in the first
place....NOT because it has become charged. After the initial current
blast has reconverted lead sulphate into acid, that acid must move out
of the way to be replaced by more lead sulphate ions convecting in
from below by the heat of charging. There's quite a circulation.
Charging too fast, say at 115A trying to force it fast, only results
in the conversion of H2O into hydrogen gas and lead oxide, that
violent gas bubbling it's doing at high charger currents, once the
initial lead sulphate to sulfuric acid conversion has wained on the
initial blast.

I suppose we could build a magnetic drive circulator pump into the
bottom of the cells under the plates and you could charge the hell out
of it, then....

Larry

Lew, try a little experiment to showcase my assertion:

Charge like hell until the voltage rises up and shut her down with NO
LOAD on the batteries. Wait 30 minutes. Charged batteries will still be
charged and immediately draw little current at float voltage.

Crank the alternator-from-hell back up and watch the current....It'll go
back to hard charging at lower-than-float voltage because the convection
in the electrolyte has replaced the supercharged electrolyte with
uncharged electrolyte to continue the replating process. The current
will drop and voltage will repeat its rise charging this hard as
electrolyte, once again, becomes saturated before convection takes place.

You can repeat the phenomenon over and over with no load on the battery
between charges.

Once the cells are TRULY charged, there will be a small current when
charging starts, but the voltage will already be high putting charging in
float mode almost immediately.

Larry
--
SLOWLY.....we recharge SLOWLY.....