How to Install & Hook Up a Second Battery for Car Audio in My Trunk

If your recent aftermarket car audio install system demands more power than the previously installed stock factory system, you might want to consider installing a second battery in the trunk. Dual battery setups are proven to stable voltage drop and provide more juice to the amplifiers. If you also notice that the car headlights dim when the bass hits at high volume levels, an dual battery system would benefit the electrical system. With adding a second battery in your car, you will need to use a isolator to provide two separate connections from the alternator. This will allow the alternator to charge both batteries as evenly as possibly splitting up the current created in the circuit. Ideally recommended the second battery needs to not be a regular starting battery but a type that is designed to store a deep cycle charge. This is since you will be adding a second car battery just specifically for the car audio system. Its designed to provide higher quality short bursts of power more efficiently, if compared to a regular starting battery.

My personal favourite type of second battery that is most suited towards high powered demanding car audio systems is by Optima. The largest yellow top optima battery which costs around about £250 pounds in the uk and around $480 in the US is the best you really need. The best combination would be to use a red top optima battery in the front for starting and a yellow top from the rear trunk. Now lets proceed with the installation of the second battery, but before we begin the best wire size to use is the thickest that is 0 gauge providing maximum current flow.

1) Mount the battery isolator into the engine bay close by next to the alternator.

2) Attach the red positive wire going from the alternator into the battery isolator terminal.

3) Attach a positive wire into the battery isolator going onto the + terminal on the first main starting battery found at the front. Also do the same but for the other side, adding a second wire onto the + terminal on the deep cycle battery into the remaining set of terminals on the battery isolator.

4) You now need to ground the second battery. This can be done by attaching it to the cars chassis, as this is the most convenient for a trunk install.

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