Battery Relocation

SimonWright · **Posted:** Tue Nov 16, 2010 7:23 pm

Has anyone ever relocated their battery? Thinking of moving the rally Focus's battery into the back. It'll probably need an enclosure since it's a hatchback. Does the ground go to the chassis near the battery, do I run a ground back to the old battery location, both? I'll probably put a cutoff switch on the dash.

Advice, tips, sources for hardware?

Thanks.

Simon
Rallye Driver

Steven Carter · **Posted:** Tue Nov 16, 2010 7:26 pm

Do your rules allow for running a non-standard battery like Braille? If so, just modify the hold-down hardware and don't worry about running battery cables to the trunk. Just another thought.

SimonWright · **Posted:** Tue Nov 16, 2010 7:30 pm

Steven Carter wrote:

Do your rules allow for running a non-standard battery like Braille? If so, just modify the hold-down hardware and don't worry about running battery cables to the trunk. Just another thought.

Yes, but there's an argument for carrying a full size battery too: you might be able to drive off and finish a stage if the alternator gives out.

Simon
Rallye Driver

Charlie Guthrie · **Joined:** Thu Aug 28, 2003 8:14 pm **Posts:** 832

Long ago when there were not strict scrutineers of tech...
The relocated battery in the MG Midget was fairly easy to install. Welding cable was the easiest, most flexible cable to run from rear to the front of the car. The ground can be tied to any "substantial" structure at the rear of the car. Keep in mind that you don't want to create a high resistance connection for the ground, so connecting to thin sheet metal would not be a good connection unless you added thick, large diameter flat washers to the connection point. Run your standard style ground strap to a solid part of the structure at the rear of the car and bolt solidly using plated or stainless hardware. (No need to run an additional ground cable forward from the battery.
At the time of the MG, I installed a plastic marine battery box in the rear spare tire well (right behind the rear axle) then used a metal frame battery tie down inside the box.
When tying down the battery remember that in the event of a sudden stop a heavy battery could rip free of a thin sheet metal floor attachment, so use very large washers or custom plates on the underside of the attachment point. I have seen some folks use the fabric strap that comes with some battery boxes to secure the battery box, but I would never rely on that strap to keep a battery in place during a "high G" situation.
Good luck, (or more of the same, since you seem to be having a fair bit of luck already),
Charlie G

Jason Tower · **Joined:** Wed Jun 11, 2008 3:31 pm **Posts:** 1173

SimonWright wrote:

Steven Carter wrote:

Do your rules allow for running a non-standard battery like Braille? If so, just modify the hold-down hardware and don't worry about running battery cables to the trunk. Just another thought.

Yes, but there's an argument for carrying a full size battery too: you might be able to drive off and finish a stage if the alternator gives out.

Simon
Rallye Driver

at the 13 hour a few weeks ago one of the miata alternators died at the 12 hour mark. we had to change batteries twice but finished the race

i relocated the battery in a project rabbit gti several years ago, wasn't difficult. run some heavy gauge wire (i used either 2 or 4ga, can't remember which) for the positive side and ground the battery to a large sturdy point on the body or chassis, making sure it touches bare metal. you can buy a battery box if desired, makes things a little easier to install and facilitates quick battery changes.

Todd Breakey · **Posted:** Tue Nov 16, 2010 11:32 pm

Jason Tower wrote:

at the 13 hour a few weeks ago one of the miata alternators died at the 12 hour mark. we had to change batteries twice but finished the race

Not only did the battery get changed twice, but this was done to finish the race.

My photo BTW.

BretLuter · **Posted:** Tue Nov 16, 2010 11:34 pm

BMW E30's and E36's have NICE heavy positive battery cables that work well for relocating batteries to the trunk.

I might know where to find one :wink:

, or you can hit up the local pick n pull junkyard, pay your $2 entry fee and they'll be glad to sell you one of those cables for ~$10 or less- IF they have one of those cars in the yard.

Charlie Guthrie · **Joined:** Thu Aug 28, 2003 8:14 pm **Posts:** 832

Nice call on the BMW positive cable Bret. That source never occurred to me to recommend to the Non-BMW crowd.

And with any luck the chief of tech never sees the photo above. Looks like those batteries and terminals are securely held in place.....
Charlie G

jimpastorius · **Posted:** Thu Nov 18, 2010 8:11 am

wow, don't use the Miata photo for any ideas...that is totally ghetto.

Go to your local welder supply store and pick up some 0 or 2 gauge wire. It is well insulated and very pliable. Plus it is fairly cheap.

Run a short connection from the ground to the chassis or through the body. The less the better. Keep the positive inside the car and inside the cage area. Any holes that the cable runs through, make sure you grommet them. For running through the firewall, I put junctions in.

I had Chris weld in a bracket with two threaded rods coming out it The battery box sits on top of the bracket with rods running up through it. So the battery is anchored down and so it the box. Simple but very effective.

As for the kill switch, make sure it actually kills the car when it is running. Every kill switch seems to prevent the car from running. But you have to know what you are doing when you want to actually kill a running car. It is pretty embarrassing when tech reaches in and hits the switch and the car just chugs right along.

WalterHouston · **Posted:** Thu Nov 18, 2010 8:32 am

I put a 50 amp fuse near the battery and used a "bulkhead" connector to go through the metal to get under the car. I made sure the cable was attached well as it ran up the frame to the engine compartment. One does not want a short in that cable. At least use heavy rubber grommets when passing through metal.

Vincent Keene · **Posted:** Thu Nov 18, 2010 9:08 am

jimpastorius wrote:

It is pretty embarrassing when tech reaches in and hits the switch and the car just chugs right along.

I can't tell you how many times this has happened at Lemons. What I can't understand is why they wait until tech to see if actually works.

jimpastorius · **Posted:** Thu Nov 18, 2010 10:01 am

Vincent Keene wrote:

I can't tell you how many times this has happened at Lemons. What I can't understand is why they wait until tech to see if actually works.

Because people do not read the rules. Plus it is a pain in the butt to get it wired up correctly.

I would not run the battery cable outside of the car. Especially on a race car and really on a rally car. For me, you are simply introducing one more point of failure. And these things have enough all ready.

Vincent Keene · **Posted:** Thu Nov 18, 2010 10:56 am

jimpastorius wrote:

Plus it is a pain in the butt to get it wired up correctly.

I guess it depends on the car? I relocated our battery to the rear and wired our kill switch at the same time. I basically ran all new wiring to all the components (alternator, battery, kill switch) and it was no problem. It took some time to make it all neat and tidy, but otherwise it was pretty straight forward.

Ryan Holton · **Posted:** Thu Nov 18, 2010 10:58 am

jimpastorius wrote:

wow, don't use the Miata photo for any ideas...that is totally ghetto.

Go to your local welder supply store and pick up some 0 or 2 gauge wire. It is well insulated and very pliable. Plus it is fairly cheap.

Car stereo shops are another good source.

THSCC Forums

Battery Relocation

Who is online