You can't directly tell from the CA and CCA ratings but that sounds like
a battery that is about 100 AH.

Knock 30 % off so the battery is never fully drained and lives longer,
divide that 70 AH by the 2.8 amps, and the battery will last about 24
hours running the heater fan all the time. Reduce that by whatever else
you want to run. I doubt that the heater fan runs all the time, more
likely only when the heater is making heat.

Mark

John C... wrote:

>........
>This may be true of the larger ones, but the 12,000 Btu
>Label says 2.8 Amp. 50 W.
>The Battery that I have is the Everstart Marine 1-n.
>Cranking Amps 1000. Cold Cranking Amps 875.
>I don't know how to figure Amp Hours from this,
>unless this is the amp hour designation.
>Also I usually sleep with the heater off, unless were talking sub freezing
>temps............
>
>