Trucks that do heavy work and spend a lot of time idling need extra power storage to get the job done. By adding a second battery to your truck, you'll be able to run electrical accessories with the engine off for longer periods of time, as well as have more cranking power when you start it up. Fortunately, many truck manufacturers have options available for dual battery setups, and the parts to do the job are available at dealerships. In this case, the project vehicle is a 1999 Chevrolet Silverado, but the process is similar for other vehicles as well.
Pop the hood and locate the spot where you'll be mounting the second battery. The secondary battery tray bolts into the core support on the driver's side as well as the fender. Mount the secondary battery tray to the fender and core support using the 3/8-inch ratchet and socket.
Place the battery in the secondary battery tray and tie it down using the 3/8-inch ratchet and socket and the factory battery tie down.
Run the positive cable from the positive terminal on the secondary battery to the positive terminal on the first battery. Connect the secondary battery using a 3/8-inch ratchet and socket, then connect the first battery by disconnecting the factory terminal using an open-end wrench, then bolt the replacement wire to the positive terminal with the other wires using an open-end wrench.
Run the replacement negative wire to a bolt on the side of the frame and secure it using the 3/8-inch ratchet and socket. Connect the other end of the wire onto the negative terminal on the battery using an open-end wrench. Start the vehicle and let it run for about 5 minutes to make sure that everything is working correctly.
