The Comprehensive Guide to Car Battery in Trunk: Maximizing Performance and Safety

When it comes to the placement of a car’s battery, the trunk is a popular choice for many enthusiasts and performance-oriented drivers. Relocating the battery to the trunk offers several benefits, such as improved weight distribution and a cleaner engine bay. However, this setup also comes with its own set of considerations and potential challenges. In this comprehensive guide, we’ll dive deep into the technical details, measurable data, and best practices for installing a car battery in the trunk.

Measuring Parasitic Battery Drain

Parasitic battery drain is a critical factor to consider when relocating the battery to the trunk. A multimeter is an essential tool for accurately measuring this drain. By using a multimeter, you can measure the tiny voltages and currents that contribute to the overall drain on the battery, allowing you to identify and address any additional drain beyond the “normal” level.

To measure parasitic battery drain, follow these steps:
1. Set your multimeter to the appropriate current or voltage range.
2. Connect the multimeter in series with the negative battery terminal.
3. With the engine off and all electrical accessories turned off, note the current reading on the multimeter.
4. A reading of less than 50 milliamps (mA) is generally considered acceptable, while anything above 100 mA may indicate a parasitic drain issue.

Gas Emissions and Battery Encapsulation

Regular lead-acid batteries vent hydrogen gas, which can be a concern when the battery is placed inside the vehicle’s interior, such as the trunk. To mitigate this risk, you can consider the following options:

1. Battery Encapsulation: Enclose the battery in a sealed, vented container that directs the gas emissions outside the vehicle. This can be achieved by using a custom-made battery box or a commercially available enclosure designed for trunk-mounted batteries.

2. Maintenance-Free Batteries: Opt for batteries that do not vent gas, such as Absorbed Glass Mat (AGM) or Lithium-ion batteries. These types of batteries are often more suitable for trunk-mounted applications, as they eliminate the need for venting and reduce the risk of gas buildup.

Cable Length and Gauge Considerations

When relocating the battery to the trunk, you’ll need to run longer cables from the battery to the engine bay and other electrical components. It’s crucial to use the appropriate cable gauge to ensure efficient power transfer and minimize voltage drop.

As a general guideline, use the following cable gauge recommendations:
– For cable runs up to 3 feet (0.9 m), use a minimum of 4 AWG (21.2 mm²) copper cable.
– For cable runs between 3 to 6 feet (0.9 to 1.8 m), use a minimum of 2 AWG (33.6 mm²) copper cable.
– For cable runs longer than 6 feet (1.8 m), use a minimum of 0 AWG (53.5 mm²) copper cable.

It’s important to note that pure copper cables are preferred over copper-coated aluminum cables, as they offer better conductivity and durability over time.

Trunk-Mounted Battery Installation Considerations

Properly installing a battery in the trunk requires careful planning and execution to ensure safety, reliability, and long-term performance. Here are some key considerations:

1. Drilling and Rust Mitigation: Drilling holes through the body shell to run wires or affix the battery can lead to increased rust. Use rust encapsulation paint or sealants to protect the exposed areas and prevent corrosion.

2. Remote Battery Cable Firewall Bulkhead Connectors: These specialized connectors allow you to pass the battery cables through the firewall while maintaining a sealed cabin environment, preventing moisture ingress and potential electrical issues.

3. Shock and Fire Risk Mitigation: Ensure that the high-power battery cables are properly routed and secured to minimize the risk of short circuits, shocks, or fire hazards within the cabin.

4. Trunk Space Optimization: Trunk-mounted batteries require a dedicated bracket or tray, which can take up valuable storage space. Consider the impact on your ability to transport luggage or other cargo when planning the battery’s placement.

5. Rust Prevention for Ground Wires: Drilling holes in the trunk for ground wire locations can also lead to increased rust. Use rust-resistant hardware and sealants to protect these areas.

6. Battery Gassing and Fire Risk: While modern batteries have reduced the risk of fire from battery gassing, it’s still important to consider this potential hazard when installing a battery in the trunk.

Trunk-Mounted Battery Pros and Cons

To help you make an informed decision, let’s review the key pros and cons of relocating your car’s battery to the trunk:

Pros:

• Improved Weight Distribution: Placing the battery in the trunk can help optimize the vehicle’s weight balance, potentially enhancing handling and performance.
• Cleaner Engine Bay: Removing the battery from the engine bay can create a more visually appealing and organized engine compartment.
• Easier Access: The trunk-mounted battery may be more accessible for maintenance and replacement, depending on the vehicle’s design.

Cons:

• Increased Cable Length and Gauge: Longer cable runs require larger gauge wires, which can be more complex to install and increase the risk of voltage drop.
• Reduced Trunk Space: The battery and its mounting hardware will occupy valuable trunk space, limiting your ability to transport cargo.
• Potential Shock and Fire Risks: Improperly routed high-power cables can pose a safety hazard within the cabin.
• Rust Concerns: Drilling holes in the trunk for wiring and ground connections can lead to increased rust over time.
• Unfamiliarity for Mechanics: Some mechanics may be less familiar with trunk-mounted battery setups, which could complicate future maintenance or repairs.

Conclusion

Relocating your car’s battery to the trunk can offer several benefits, but it also requires careful planning and execution to ensure optimal performance, safety, and long-term reliability. By understanding the technical details, measurable data, and best practices outlined in this comprehensive guide, you can make an informed decision and successfully install a car battery in the trunk of your vehicle.

References:

• Idiots Guide to Tracing Parasitic Battery Drain in Modern Cars
• Battery Relocation to Trunk: Pros and Cons
• Pros and Cons of Putting Battery in the Trunk