2 - 6 volt batteries or 2 - 12 volt batteries or...

Junkyard special to thousand dollar lithium battery this is the perfect way to destroy it...

"I left them hooked up for a bit too long I suppose"

While on the road the tow vehicle replenishes power used for refrigerator, etc. via it's charging system.

I am not fixating on price. My decision is based solely on fitting what is needed not dogmatic reaction to "What Seems To Be Right".