Open the bonnet and boot. Disconnect the vehicle's battery by removing the negative (ground) cable with a wrench.
Mount the battery in your car, truck or SUV (the battery mounting location may vary). Place the battery box where you want it. Typically, the boot is the best mounting location. Place a drill bit into the drill motor chuck and drill through the mounting bracket of the new battery box and into the boot floor. Use the mounting hardware that came with the box and insert bolts through the holes you just drilled. Tighten them with a wrench.
Drill an additional hole beside the battery box to run the new positive battery cable through the boot floor. To avoid cutting the cable, place a rubber grommet in the hole.
Mount the isolator switch. Place the isolator switch in the engine compartment. The inside of a fender well or the radiator support works best. Place a screwdriver bit in the drill motor. With the isolator in place, run a self-tapping screw through a hole in the mounting bracket and into the fender well. Repeat this for the other mounting hole in the bracket.
Install the new battery in the newly mounted battery box in the boot and secure it with the included mounting hardware. Tighten it with a wrench. Run a piece of 4-gauge wire from the battery box in the boot through the rubber grommet and along the chassis into the engine bay stopping at the new isolator switch. Cut the wire with wire cutters. Secure the wire along the chassis with plastic zip ties.