Re: [VAC] Battery charging and discharging rates

["Dr. Gerald N. Johnson" <geraldj@xxxxxxxx>]

Deep cycle batteries withstand deep discharges than starting batteries
because the lead of the plates is made thicker and stronger to better
withstand the pressure of the expanding lead sulfate that is created on
discharge.

The precise terminal voltage depends on temperature as well as the
design full charge specific gravity of a battery. Deep cycle batteries
tend to be designed for a lower SG than starting batteries because the
lower SG leads to longer life from not being quite as corrosive. The use
of a lower SG does reduce the capacity of the battery.

When I swapped a '68 VW engine into my '64 (12 V generator on the
engine, 6 volt car) I built an electronic voltage regulator to run the
12 volt generator at 6 volts since it wasn't practical to mount the 6
volt generator on the 12 volt mount. A couple years later I replaced a
worn out battery with a new one selected off the shelf to have the
latest date code. Three years later that VW sat for 6 months or longer
and that battery was completely dead when I drug the VW out of the
garage to sell it to my parents. After charging with a charger to get
the bug running that battery lasted another three years... I think the
key was care in not over charging it because my electronic regulator was
correct to the nearest .01 volt while the factory regulator was correct
to the nearest 1 volt which abused previous batteries severely.

Gerald J.