if i put a second battery in my cehicle will it mess up any of the elsectrical and how would i go about doing that? do you just grount both and link the positives?

 

no, you need a battery isolator.

what ahppesn is that the batteries will have a slightly different charge and transfer bac k and forth for hours and hours, and just drain each other. so you need to install a isolator for this.

 

where and how much are they

 

ebay, stinger, streetwires whatever.. no clue on price