i have an international eagle semi truck with a 12v system. i have two 24v bubblegum style caution lights mounted on top, with 2 12v batteries forming an independed 24v electrical system. can i charge these batteries individually off the 12v system, and do i need a battery isolator to do this? also the 24v lights are grounded to the truck, do they need to be grounded all the way back to the battery?