In this post, we talk about why you would want to relocate your battery from the engine bay and how to upgrade the wiring to keep everything working.
Why Relocate the Battery?
Moving the battery out of the engine bay can help make room for modifications such as front-mount intercooler piping, intake components, or other performance upgrades. Some owners relocate it to the trunk of the car to improve weight distribution, while others simply want to clean up a crowded engine bay.
Whatever the reason, relocating the battery involves more than extending a positive cable to the rear of the car. The charging system, starter circuit, electrical protection, and grounding system all need to continue working correctly.
How to Relocate Your Battery from the Engine Bay to the Trunk
First off the mechanical bits:
Mechanically, the process is straightforward, but taking a few extra precautions will make the installation much easier.
Start with the vehicle completely turned off, the key removed, and all accessories switched off. Disconnect the original battery’s negative terminal first, followed by the positive terminal, then remove the battery and factory hold-down from the engine bay.
Mount the battery securely in the rear using a properly sized battery tray or box and a strong hold-down that prevents movement in every direction. We suggest following the battery mounts' specific install instructions to make sure the battery is secure. Some basic tips include making sure the location is clear of other components like the fuel tank and brake lines, and that there is room for a battery box (if using a lead-acid battery) before finalizing the battery mount location.
The next step is the wiring, which is described below. Once the mechanical mounting and wiring are complete, reconnect the positive side first and the negative side last, then confirm that the battery is secure and every connection is tight before starting the car.
Wiring the Battery Relocation
iWire has designed our Battery Relocation Kit to remove any guesswork. We've curated all of the individual parts so you get a Subaru-focused wiring solution designed for a safe, reliable, and clean installation.
What Is Included in the iWire Battery Relocation Kit?
The kit includes the major electrical components needed to relocate the battery without building your own high-current cables or sourcing mismatched parts.
Key components include:
- Preassembled, large-gauge battery cables
- Clearly labeled connection points to make installation easier
- A bolt-on engine-bay bracket
- A protected power distribution stud for the original front battery connections
- A manually resettable circuit breaker near the relocated battery
- The necessary connection point for the battery and engine grounding system
- Vehicle-specific components where required
For applicable FA-platform vehicles, such as the 2015–2021 WRX, the kit also includes a battery-sensor wire extension so the original battery monitoring system can continue to function with the battery moved to the rear.
The battery and battery tray are not included. This allows you to select the battery size, style, and mounting solution that best fits your build.
What makes our Battery Relocation Wiring Kit Different?
Clearly Labeled Connections
The cables are labeled to help identify where each connection belongs. Instead of interpreting a generic diagram and designing the system yourself, you can match the labeled connections to their intended locations.
Proper Engine Grounding
The system does not treat the rear chassis as the only ground path. It accounts for the important electrical relationship between the battery, engine, intake manifold, alternator, and ECU.
Integrated Circuit Protection
A resettable circuit breaker is included as part of the system rather than being left as an optional component for the installer to source. Or worse, relocating without a circuit breaker and draining your battery.
Clean Engine-Bay Integration
The bolt-on bracket and power stud provide an organized connection point for the electrical circuits that originally attached to the battery in the engine bay.
Support and Installation Documentation
The kit is backed by iWire’s Subaru wiring experience, installation documentation, and customer support. iWire products are designed around proper materials, reliable connections, clean fitment, and an installation that feels as close to factory as possible.
Click here for our YouTube install video!
Subaru-Specific Design
The kit is designed around the way Subaru starting, charging, and grounding systems are configured. Vehicle-specific options and additional components are included where platform differences require them.
*No specialty tools for large gauge wires needed!
Click here to purchase iWire's Battery Relocation Wiring Kit
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