Outfitting a trail rig can add greater strain to the electrical system. Adding on a winch, air compressor, fog lights, driving lights, a spot light, electric fuel pump, and a stereo amp can really tax the battery. A great way to combat that strain to to install dual batteries. This is especially true when using a winch, which can draw big amps for an extended period. These kits are designed to mount two batteries in place of the factory single battery location.