Has anyone relocated battery to the trunk?

[tonytiger]

I was wondering could it wice to locate the battery to the trunk. I haven't weighted my wet cell battery, but I'd guess it weights something like 10 to 15 kg. Moving the battery to the back would balance the car nicely.

Has anyone done it?

If so:

How did you connect the original plus and minus from the back?
Did you drew two cables to the front or did you ground the minus to the chassis in the trunk?
From where did you drew it?

What size electric wire did you use?

How did you support the battery to trunk? Did you make a closed case to it?

Where did you exactly put it?

Have you discovered anything special about the behaviour of the car? No battery fumes at the trunk?

Have you measured did the center of gravity move up or low vertically? In other words: Is the battery higher or lower from the ground?

Is this leagal by your traffic laws - mine might be different?



Any pros and/or cons you might think about doing this?

Sould one be worried about something related to the electricity (wires running under your feet, how the grounding works, is the wire used sufficient sized etc)?


Might forgot something...

Thank you in advance.



tony

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[tmaler13]

I'm tossing around the idea, I figure i'll use one of those gel batteries and get the battery relocation kit from www.summitracing.com for $42.00
It comes with everything you need including a case.


-Terry

[leoneo01]

I used a Moroso battery box. It is made of a non-conductive material. It is sealed so the gases don't enter into the cabin. It does have a vent tube which is used to expel the gases outside the car.
I mounted it at the right-side of the trunk near the tail light. I found a rubber grommet on the right-side wheel well which I drilled a hole in for the vent tube. It will stick over the spare tire well, so I mounted it on top of an aluminum plate to help support the battery. I did mount it originally without the plate and it did hold up well with just the box supporting the battery. I drilled three holes through the floor pan - two for the battery hold-downs and a third to secure the plate. With the plate, I had to modify the spare tire cover and the trunk carpet. The cover won't fit under the plate with the spare tire in place.
I ran the positive cable, which is connected to the original positive cable. I passed the positive cable through a rubber grommet on the firewall, which is located just below the brake booster, and ran it down the side of the car with the fuel lines. It crosses under the rear passenger seat to the right side and into the trunk. The positive cable I used is made up of two cables so the connection was exposed metal. I thoroughly insulated it ( I did not insulate it on my first try and singed the bottom of my rear seat - I knew it caught on fire...there was smoke).
I ran the negative cable to a bolt in the trunk. On the right side of the trunk behind the trunk liner, there was a hole. I sanded it down to the metal and attached the cable with a bolt. At first it was not sanded enough, and I heard a whine through my radio. Now, I hear it sometimes (if I try), but it is very quiet. The cables I used are two gauge.
Now my car is very prone to oversteer. I have stock suspension with just a larger rear sway bar. With steady-state cornering, my front stays tucked in with the tail a little out.

[tonytiger]

Thank you both.

Summitracing is a bit far away from my whereabouts Nice set though and an affordable price.

Moroso box is a bit expensive at least at Summit's.

Is there some reason beside the practicality for mounting the battery on one side of the car? Wouldn't it be best to put it in the middle of the trunk?

I though the grounding would be a problem - as it seems to be. Does our cars have some supprt bars in the chassis without any breaks in the metal which could be used as grounding by connecting the negative terminal under the hood to it?

Is the gauge wire how heavy? If not it could be wise to run both negative and the positive to the original cables.

Sorry for my lack of understanding of English, but the positive cable is going from the front to rear inside the Subie, right?

Leoneo01 you think the relocation of the battery made a difference? The bar by itself propably causes a lot of the oversteering...



tony

[Patrick Olsen]

Generally cars are heavier on the driver side since that's where the driver sits. So mounting the battery in the rear on the passenger side will help balance the front-to-rear weight distribution and the left-to-right weight distribution.

I've heard of people having good success using 0/1-gauge welding cables. It's more flexible and easier to work with than your typical 0-gauge or 2-gauge power wire that you buy at a stereo shop, and it's clearly capable of flowing plenty of juice.

As for grounding, the technique that I've heard works the best is to ground the battery somewhere right there in the trunk, and then run a wire from there to the original ground up in the engine compartment.

Pat Olsen
'97 Legacy 2.5GT sedan

[Tim Smith]

I have relocated many batteries. I do it the same way everytime.

I use 1/0 welding cable (flexible). Both sides of the cable go back to the battery. Negative too.

I sodder the joints under the hood cover them with weather proofingand tape.

I bolt the battery (gel Cell) to the chassis and then run a ground wire in addition to the wirte coming from under the hood. Have never failed me and made it through 2 wrecks on the track.

I either put it behind the passanger seat or against the passanger side of the rear seats.

[leoneo01]

My brother has the same set-up (stock suspension and larger rear sway bar) on his '01 RS, but without the relocated battery. His car reacts more to lift off oversteer. It comes out faster due to the weight transfer.

[tonytiger]

Kiitos.


Pat Olsen: You have a good point there about the weight distribution

How expensive is the welding cable? How heavy is it?



tony

[Tim Smith]

Welding cable is just like regular cable it is just WAY more flexible and has a rubber shething instead of flexible plastic. The wire itself is a lot of smaller stands of copper and conducts electricity better. Electricity rides on the outside of a conductor, so the more surface area the less the internal resistance. But the less the heat transfer also. Welding cable is more expensive but it will make your life less painful when routing the wire through the car. I recommend it highly. Check hardware stores and welding stores for availibilty.

[sleepy-scoobie]

I've been considering this, as well. I figure the WRX is around 3080 lbs, and a battery weighs around 30 lbs, so moving the battery (1% of car weight) from the hood to the truck shifts the weight distribution from 59/41 to a much improved 57/43. Of course, as Pat noted, this depends on where you put the battery. Nice how it's currently at the very tip of the hood... moving it will move more weight from the edges of the car. This is sound, yesh?

I was thinking of sticking the box right behind the rear seat in the trunk. This will reduce the car's polar moment of inertia (resistance to rotation) at the expense of slightly better balance (if I put the battery further back near the bumper).

Going from 59/41 to 57/43, all other things held constant, will definitely make the car more tail happy. However, balance can easily be dialed in, and the end result will be better handling compared to the 59/41 balance. Of course, I was thinking about ditching the spare... that would probably bring me to 58/42...

[Revision]

4 gauge cable. Routed between the rear partitions, under the passenger seat along the trunk-pop cable, into the engine bay through the grommit under the brake booster connected to the original positive connection. Nothing but amps.

4 gauge cable for the ground. Bolted to an unused bolthole under the rear seat. Paint sanded off first.

200 amp switch type breaker mounted on the battery box cover.

Continutity and resistance tested at the engine bay.

Morosso battery box mounted with two holes drilled right at the edge of the seam weld for the spare tire. Placed next to the passenger side tail light.

Used an Optima battery so no vent holes needed. (Heavy SOB)

I've been sucessfully running this setup with a TecII, lightly modded sound system (head unit and speakers), and higher wattage headlights for the last few months.

[Layman]

Originally posted by sleepy-scoobie
... to a much improved 57/43.

You mean 58/42, right? If you're only moving 1%.

Assume that the car weighs 3000 lbs even. That means that 59% = 1770 lbs and 41% = 1230 lbs. Move 30 lbs from the front to the rear and you now have 1260 lbs in the rear, which is 42% of the total weight.

Just to be anal.

In my opinion, this isn't a worthwhile mod for a daily driven car. I use my trunk often, so the loss of trunk space is what really prevents me from doing this. But if you can afford the space, then go for it!

[Tangmere]

Conventional thinking puts the battery on the passenger side, but Subarus are anything but conventional, the battery goes on the drivers side. Subaru planned for the battery to be on the dirvers side and the car is balanced so. This is going by what those fine folks at Rallispec say. They corner weighted the car before and after to make sure (the car did not have coil-overs, btw).

Mark