Two big 6v golf cart batteries connected in series for 12v
Or two big 12v industrial sweeper batteries connected in parallel ,
A 300 to 600w inverter will supply enough power for your Xbox and TV,
But surely you are aware of the Van movement and the tiny house movement,
You might find more direct hands on info in online chats there than here, we are always glad to lend advice and share knowledge
I can explain it to you.
But I Can Not understand it for you !
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1997 F53 Bounder 36s