I'm making a teardrop for weekend trips. We need a small heater to take the chill out on freezing nights. Only needs to work for 1 night then will be back home to charge it. Using a walmart 400w inverter and a 400w tiny ceramic heater. Heater only works for a few minutes per hour. I was calculating as follows

400w x 12hr = 4800wh

4800wh x 1.3 = 6240wh

6240wh ÷ 12v = 520ah

with walmart deep cycle batteries only being 105ah I'd need 5 of them? Is this correct?

400w x 12hr = 4800wh

4800wh x 1.3 = 6240wh

6240wh ÷ 12v = 520ah

with walmart deep cycle batteries only being 105ah I'd need 5 of them? Is this correct?

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