Gone Outdoors

How do I Install a Dual Battery System in a Vehicle?

by Stephen Benham

Installing a dual battery system in a vehicle can be done one of two ways, depending upon electrical requirements. Installing dual batteries in series combines the output voltage of the dual batteries but maintains the same capacity. For example, two 12-volt batteries wired in series, provide an output of 24-volts. Dual batteries wired in parallel, does not increase output, but doubles capacity. If you need to increase capacity, wire the batteries in parallel; for increased voltage, wire in series. Both methods of installing a dual battery system are moderately easy.

Series Wiring

Check the voltage of the vehicle before installing a dual battery system. The vehicle must be able to operate on the combined voltage of the dual batteries. If the combined output exceeds the vehicle's voltage, you will damage the electrical system and blow its fuses. If installing two 6-volt batteries, the car's voltage must operate with 12-volts.

Remove the battery cables from the terminals of the existing battery using a wrench. Position the second battery as close as possible to the existing battery and fix it in place firmly.

Connect a new battery cable to the negative "-" terminal of the original battery and connect the other end to the positive "+" terminal of the second battery.

Connect the negative or black battery cable from the vehicle, to the negative terminal of the second battery.

Connect the positive or red battery cable from the vehicle to the positive terminal of the existing or first battery. The vehicle operates with a dual battery system in series.

Parallel Wiring

Remove the battery cables from the existing battery using a wrench. Position the second battery as close as possible to the existing battery and fix it in place securely.

Connect a new battery cable to the negative terminal of the existing battery and connect the other end to the negative terminal of the second battery.

Connect a new battery cable to the positive terminal of the existing battery and connect the other end to the positive terminal of the new battery.

Connect the negative cable from the car to the negative terminal of your existing battery. You now have two cables attached to this terminal.

Connect the positive cable from your car to the positive terminal of the existing battery. Check all the cables are firmly fitted. When finished, this dual battery system operates in parallel.

Items you will need
  • Wrench
  • Two new battery cables

About the Author

Stephen Benham has been writing since 1999. His current articles appear on various websites. Benham has worked as an insurance research writer for Axco Services, producing reports in many countries. He has been an underwriting member at Lloyd's of London and a director of three companies. Benham has a diploma in business studies from South Essex College, U.K.

Photo Credits

  • dead battery image by Katrina Miller from Fotolia.com