Most cars and trucks have the battery located within the engine compartment. This places it close to the starter, shortening the cables, thereby reducing the drop in voltage often caused when long cables are used. However, this is often not possible in early hot rods that have small engine bays or in vehicles with extremely large engines.
This makes it necessary to place the battery in the trunk or in a box attached to the inside of the frame rail. Installing the battery in the trunk is the preferred option because this provides better access and protects the battery from the elements. The process is simple as long as a few basic mounting practices are followed.
A battery box must be used to isolate the battery from any other items in the area and it should be securely mounted to the floor or on a platform within the trunk. With lead/acid batteries it is important to mount them level and make sure that they are vented properly. The new sealed Spiral Cell lead/acid batteries like the Optima don’t have to be mounted level and don’t need the venting but still should be isolated in a battery enclosure of some type.
Cables from the battery to the starter need to be of a bigger gauge (01 usually) to compensate for the voltage drop created from the longer run. A short ground cable of the same size can be run to the frame but another short cable of the same size should run from the engine to the frame to complete the ground circuit.
The photos and captions chronicle the installation of an Optima battery in a Bitchin’ finned aluminum battery box within the trunk of my deuce hi-boy roadster. It is placed on the left side because the starter is located on the left side of the Nailhead Buick powering the roadster. Most popular engine choices have the starter on the right so it may be more convenient to place the battery there.
Remember, newer vehicles with on-board electronics such as computers, alarms, etc, require battery power to retain system memory while the vehicle is parked. If the vehicle is to be stored for long periods you should use a maintenance charger to compensate for this drain. This charger should be voltage regulated between 13.2 - 13.8 volts, 1 amp maximum. On older vehicles, without electronics, disconnect the battery cables when the vehicle is not being used for extended periods.