Dennis, Michael,

Thanks for replies.

Michael, I have a 4AWG wire feeding the 1250W inverter, and it's only about
2 feet long, so it ought to be large enough. I charged the aux battery with
no load on it (fridge and inverter are the only things wired to it) for
about 45 minutes to get to 12.30 volts. In an hour and a half of using the
fridge it dropped from 12.3 to 10.62 volts, about the lower limit for any
cooling. Seemed to bounce back some when I turned the fridge off.

Dennis, if 800 watts at 120 volts fried the battery--then what the h**l do
they sell 1200 watt inverters for? I thought you were supposed to be able to
use Skilsaws etc. with the larger inverters. These are designed to go into
normal cars and trucks with normal batteries, no? Or was it the length of
time using it that whacked the Optima (maybe five minutes, no frothy milk on
the coffee) ?

So what I'm hearing is that the aux battery isn't holding a charge, which
explains why the voltage during charging is lower than on the vehicle battery.

Next time I get a degree, it's going to be electrical engineering.