The high-power amplifiers and bass boosters of today's car stereos make listening to the music feel more like attending a concert. The speakers are powered by huge amplifiers and cross-over boxes designed to maximize performance and sound, and many of the higher-end stereo systems even incorporate high-energy capacitors to store energy, which enable the extreme amounts of bass to reverberate and be heard for several city blocks. All of this power drainage is tough on a charging system, and many people install high-output alternators in their cars. The really smart people add an auxiliary battery.
Park your vehicle. Turn the engine off. Open the hood and disconnect your vehicle's battery by removing the negative terminal connection with a wrench. Open your trunk.
Decide on the location for the second battery. In most systems, the area right beside the amplifiers in the trunk is the best and safest location. This also puts the new battery in close proximity to the stereo components, making the wiring a bit easier. If your amplifiers are mounted in a location other than the trunk, you could mount the battery in close proximity or simply route the wiring from the trunk-mounted battery to the amplifiers. Space will dictate the location of your new battery.
Mount the battery. Locate the battery box where you want it in the vehicle. Place a drill bit into the drill motor and drill through the battery box's mounting tabs and into the trunk floor. Using the hardware that came with the battery box, place a bolt through each of the mounting tabs on the box and the holes you drilled. Tighten them with a wrench.
Wire the battery positive side. Using a heavy gauge copper wire of at least 2 gauge, run a piece of wire from the positive side of the new battery to the power lug of the closest amplifier. Using a wire stripper, remove just enough of the cable's protective plastic coating to allow you to crimp a terminal end to each end of the cable (wire). Attach one end to the positive terminal post on the battery and the other to the power lug of the amplifier. Tighten the connections with a wrench.
Run a ground cable from the negative side of the new battery to the floor of the trunk. Tighten the battery clamp with a wrench and secure the other end to the trunk floor by inserting a large self-tapping screw through the cable eyelet and screwing it tightly to the trunk floor with a screwdriver bit mounted in a drill motor. Reconnect the vehicle's original battery ground cable and tighten it with a wrench. Close the hood and trunk.
