Battery capacity with engine off

[RMcG]

I am interested in running a fan in the car at night (with the engine off) while I sleep in the car. I have two fans. Fan #1 runs off 12 volts 0.8 Amps 10 watts. Fan #2 is AC (117 volts AC, 20 watts of less 50-60 Hertz) and runs off an AC-DC converter in the 12 volt DC power outlet.

QUESTION: How long can I run one of these fans without discharging the battery enough to keep the car from starting?

Thanks,

RMcG

[CTScott]

If the stock battery is rated for 45 Ah (Amp hours), then you can safely discharge it to 1/2 of that before damaging the cells. Unfortunately, at 22.5 Ah of charge, it may not have enough power to crank the starter, so I would limit myself to about 11 Ah of discharge before running the engine long enough to fully recharge the battery. With that said, that would mean that you could theoretically run your 0.8A one for 13.75 hours. The AC fan running off of the inverter will draw quite a bit more because of the inefficiency of the inverter.

[mazilla]

Add a second battery, and or a battery switch...like on a boat.

[RMcG]

Thanks Scott and Mazilla. RMcG