How to Wire a Trunk Mount Battery


Moving the vehicle's battery to the trunk is a common high-performance modification that increases traction and handling by increasing the weight on the rear tires. Wiring a trunk-mounted battery is relatively straightforward, though it does take time to properly route the positive battery cable to the starter solenoid.

Things You'll Need

  • Petroleum jelly or oil
  • Electric drill
  • String
  • Tape
  • Rubber grommet
  • Wire cutters
  • Metal eyelet
  • Wrench
  • Wire mounting brackets
  • Battery terminal clamp
  • Install the battery's ground wire. The ground wire is typically installed inside the trunk next to the battery. The battery's ground cable can be bolted to any unpainted area of the vehicle's frame or sheet metal. Once the cable is bolted into place, coat the bolted tip of the cable with petroleum jelly or oil to prevent corrosion.

  • Drill the hole through which the battery's positive cable will enter. The positive battery cable must be routed from the trunk to the starter solenoid. Therefore, a hole must be drilled through the trunk for the positive cable to reach the solenoid. Use an electric drill to drill a 1/2 inch hole through the floor of the trunk, taking care not to drill into the gas tank.

  • Determine the proper length of the positive battery cable and where that cable will be routed with a piece of string. Insert a rubber grommet into the hole cut though the floor of the trunk to prevent the metal from cutting into the battery cable once installed. Tape one end of a piece of string next to the positive battery terminal on the battery, then feed the opposite end of the string through the grommet. The string should then be extended along the vehicle's frame to the starter solenoid to determine the proper length of the battery cable and where the battery cable will be routed underneath the vehicle. Cut the positive battery cable to the chosen length of the string with wire cutters.

  • Place a single metal eyelet over one end of the positive battery cable, then crimp the eyelet onto the cable with wire crimpers. Bolt the eyelet to the positive side of the starter solenoid with a wrench; the positive side can be identified by the "+" symbol next to the post on the solenoid. Run the battery cable along the path chosen by the string, through the rubber grommet installed in the trunk and to the positive terminal on the battery.

  • Install several wire mounting brackets onto the positive battery cable. Each bracket can be pulled apart and slipped onto the battery cable. Although the number of brackets varies depending on the length of the vehicle, the purpose of the brackets is only to ensure that the battery cable rests securely against the bottom of the vehicle. Drill a hole through the frame of the vehicle with an electric drill, then secure each wire bracket to the vehicle's frame with a single bolt installed with a wrench.

  • Attach a battery terminal clamp to the free end of the positive battery terminal by first inserting the tip of the cable through the clamp, then by tightening the two bolts on the clamp with a wrench. Slide the clamp at the end of the positive battery cable onto the positive battery terminal, then tighten the single nut on the clamp with a wrench to complete the installation.

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  • Car Craft Magazine; How To Install a Trunk-Mounted Battery the Right Way; October 1994
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