Amp usage

You're basically on the money old mate.
Suggest you buy a fire coffee pot. You can't expect 800W out of a 12V system for very long. I doubt it would work satisfactorily even with the engine running and if your alternator could put out 100 amps.

Yeah, your maths are right. But factor in the inefficiency of an inverter and the current at 12V will be even higher than that. It's not at all practical.

Thanks guys,
I'll save that option for a 'BIG4' caravan park:) plunger here I come

Marcel

A few corrections here. To cater for the losses in the inverter you divide by 10 and not 12. That gives a current draw of 80 A. If you run it for 10 minutes that would be 80/6=13.3Ah (at this stage you should be talking amp hours and not amps.)

However that is not the full story. You have not taken Peukert's Law into account. Batteries are not a linear device. If you have a 100 Ah battery you will only get 100 Ah out of it if you discharge over a 20 hour rate (5 A current draw for 20 hours.) If you discharge it at a lower rate you will get more amp hours out of it. If you discharge it at a higher rate you will get less. When you apply Pukert's Equation to your exercise you could be drawing twice the 13 Ah from your battery.