Relocating Your Battery From The Engine Bay To The Boot.  

I often hear questions about battery relocation and thought someone might be interested in a no-nonsense explanation.

Benefits:

Better weight distribution for improved handling
Increased engine bay space
Increased battery performance and life by reducing operating temperature

This information has been compiled with the help of Battery World franchisees and staff who do these types of conversions everyday.

All batteries rely on an internal chemical reaction to generate electrical energy, which creates toxic gases as a by-product and must be either released or reconstituted. These gases can be safely ventilated in an engine bay, but once the battery is mounted internally, they can easily build up to dangerous levels.

Also, high engine bay temperatures can cause the battery's rate of chemical reaction to accelerate and shorten its life.

Important features for a boot mounted battery are:

High Power Capacity to turn over large volume and high compression engines
Vibration Resistance
Heat Resistance
Don't vent gases
Mountable on almost any angle and won't spill electrolyte

IMPORTANT: It's a waste of time and money going through this process with the intention of installing a cheap battery.

We recommend using a sealed AGM (Absorbed Glass Mat) type battery, but a maintenance free battery with a breather hose to the external atmosphere (via the boot floor) will also do the job.

RACING: If you want to go racing, make sure you refer to the technical or category rule manuals from:

CAMS - drift, sprints, road course, rally (http://www.camsmanual.com.au/)
ANDRA - drag racing (http://www.andra.com.au/)

STREET: If you want to modify your battery location and drive on the road you must comply with your State Transport Authority.

Important issues to be aware of:

Mounting
Grounding
Resistance
Ventilation
Vibration

Parts List:

Battery
Battery box
Battery mounting bracket kit
Cables - OB & S diameter and 4m lengths x 2 (You need the thickest cable possible to accommodate voltage loss from the resistance of the extra cable length. This will also help avoid a mountain of possible earthing problems later on.) OR?
2B&S has proven suitable for turbocharged vehicles with low compression engines provided the connections are clean and tight.
Crimp lugs x 2
Brass Terminals x 2 (match size to the battery terminals you?re purchasing!)
Rubber grommets x 2
Anti-zap
Terminal protection spray

Tools required:

Drill
Shifting spanner
13mm socket
Crimping pliers
Cable cutters


Some recommended batteries:

Optima - Their Yellow Top has massive cold cranking amps, very high vibration resistance, high under-bonnet temperature capability, extra long life and deep cycling ability to run serious sound systems for very long periods.
Odyssey - available in much smaller external dimensions and offers further weight savings for racing applications.
Century Hi-Performance maintenance free range - has an option to vent via a plastic hose to outside the boot and can provide a cost effective alternative, but a bit more installation work is required and you must regularly check it.

Steps:

1. Disconnect battery from engine bay leads (Important: Disconnect your earth (negative) lead first, followed by live (positive). Reconnect in reverse order).and remove from mounting bracket. We recommend running 2 cables from the boot to the engine bay. One from the battery positive terminal to the engine earth. One from the battery negative terminal to the starter motor. Then, a short earth lead from the starter motor to the chassis earth.
2. Find a hole in the firewall that will allow both cables to be threaded through. If no existing hole exists, drill 2 holes to enter behind dash on passenger side.
3. Peel back front passenger footwell carpet, slide rubber grommets over cable and then feed cables from inside in to engine bay.
4. To join the live terminal to the rear mount cable we suggest removing the original brass battery terminal from the cable and replace with a copper sleeve and then swage the cable to the existing terminal connections. This should then be double wrapped with high voltage shrink wrap (thicker walled and encased in glue type resin). Swaging is joining, two or more cables in a barrel / straight type joiner under pressure by use of crimps.
5. Fit rubber grommets to seal holes in the firewall.
6. Cable-tie both battery cables to the chassis clear of any moving or hot parts like exhausts and turbo-chargers.
7. Feed remaining cables under the carpet toward the boot.
8. Choose a location for battery box to mount to chassis. Preferably to the side or rear where you can mount to solid chassis metal and will be able
9. Drill holes for bracket kit through box and boot floorpan. Battery box cannot be fixed to the chassis and then just sit battery in the box. The battery must be clamped to the chassis directly, sandwiching the base of the battery box.
10. Sit battery in battery box and clamp in place.
11. Lay out route of cables in boot and zip tie in place. Make sure the cables will be out of the way when carrying stuff in the boot and also so they can easily be pulled out of the way to install and remove the battery.
12. Measure cable length to reach battery terminals and cut. Leave a bit of extra length for attaching the brass terminals and slack for pulling them on and off.
13. Connect Anti-Zap across positive (earth) and negative cables. This is often over looked, but is an excellent and in-expensive safety measure for yourself and your car?s expensive electronics and software from voltage spikes.
14. Feed cables through the holes in your battery box lid.
15. Attach brass terminal clamps to both cable ends.
16. Rough up the battery?s terminal and the matching inside surface of brass terminal clamps.
17. Connect earth lead to positive terminal on battery.
18. Connect negative lead to negative terminal on battery.
19. Spray both terminals with terminal protection spray. This simple action can prevent corrosion and extend the life of your expensive battery.
20. We suggest anyone contemplating doing this for legal road use has their engineer of choice approve the install. There seems to be some grey areas in the legislation, everything from grade and size of bolt, material used to tie battery down and ventilation - if applicable. The rule book can be overwhelming to read and at the end of it, is very much open to interpretation.

If you have any queries, just go and talk to your local BatteryWorld guy as he's probably into cars like you.
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