[heavyj]

The things I check when i want to maximize battery life over night is:

Your TV(s) may or may not be 12v. I'd have them both ways so check that.

For sure your TV AMP is 12v and you should check that for unnecessary power draw.

You'll want to triple check that no unnecessary exterior lights are left on (as I've done this many times) to maximize whatever life you'll get our of your battery that night.

My 2010 Silverado has a battery disconnect feature where it will disconnect any external power draws to preserve enough battery to start the motor in the morning. If I didn't have that I'd disconnect from truck.

Walmart is a good idea because there is a possibility that your battery might need to be replaced. I suppose walmart would have something you could use.