What are the best batteries and where to buy them?

I like Deka also.
I understand that they make batteries for NAPA.
Two six volt in series might be better, but if you are in the middle of nowhere and one six goes bad, you are up the creek. But if you have two 12 volts in parallel and one goes bad, just disconnect it. You will only have 1/2 battery power, but you are not dead in the water.

Dusty