Relocating a Battery to the Trunk/Boot

Moving the battery to the trunk/boot

Purpose

Cars handle much better when the weight distribution over the axles is as close to 50% / 50% as possible. You can help move some of the weight to the rear of the car by relocating the battery to the trunk. The end goal is to have a battery in a safe box located in the trunk. The wiring will be ran through the inside of the car. Battery life extends when being stored in a colder location. Engine heat and hot days sitting in the sun can cause batteries to fail after 1-2 years. 
What you need?
  • Marine-grade battery box. Aluminum is Best but plastic can be used
  • Roughly 6 Sheet metal screws and Cushion Clamps.
  • 15-20 ft of 1 GA Positive Battery Cable Red
  • 2 Battery Terminals 
  • 2 ft. of 1 GA Negative Battery Cable Black 
  • 1 or 2 Grommets for Firewall and Trunk Entrance
  • 2 battery connectors 1 for Ground 1 For Starter
  • Hammer Lug Crimping Tool 

 

What to do?

  • Make sure to run a ground strap from the motor to the body.  
  • Don't run the new wiring UNDER the car.  Go through the interior under the carpet
  • Watch out for the movement of the seat rails. 
  • Often you can find unused grommets but you can always drill a hole and add one. 
  • 4 Gauge wire is said to be the minimum acceptable gauge. Anything less is dangerous.
  • Leave plenty of Contact area for your ground to battery. Mount to shiny metal, no paint. 
  • Watch out for any hot engine parts such as exhaust when running your wires from the starter.

 

Directions:

  1. Remove battery
  2. Remove the ground wire
  3. Remove the battery tray if possible
  4. Test fit your power cable through the interior of the car
  5. Install the Positive Cable to the starter and attach any other wires. 
  6. Mount the battery box in the trunk. Leave room to remove the lid.
  7. Cut any excess cable for a nice fit.  
  8. Use the Hammer Crimp tool to install terminals. Some cables come pre crimped with terminal. 
  9. Mount a ground strap from the body of the car to the engine.
  10. Recheck the wiring and Reconnect the battery. 
  11. Have Fun!

 

Purchase a kit here: 

https://lermscustoms.com/collections/mercedes-benz-tools-and-parts/products/batteryrelocationkit

 

 

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1 comment

  • So i wanna do this on my w123 and my friends says I need to add a fuse to the positive side? Do I need to ad one or can I just run it to the starter like factory

    Ryan Rudolph

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