Battery Relocation… Balancing Act.

By: Bob Goodson
May 31, 2020

Author: Michael Yount

Although the little car is light (right around 2050 lbs.), the engine sits well forward in the chassis.  And the battery is right behind the driver’s headlight.  So moving it to the trunk will help significantly with front to rear balance.   A series 35 lead acid battery weighs about 39 lbs.  Because it sits out in front of the front axle-line and will be relocated significantly behind the rear axle, there’s a leverage effect.  So moving a 40 lb. battery the way I am results in about 60 lbs. coming off the front tires and being added to the weight over the rear axle.  Playing with corner scales you can see this — even though the result may seem a bit counterintuitive.  To illustrate the change – lets say the car has 56% of its weight over the front wheels – call it 1150 lbs.  Which leaves 900 lbs. over the rear wheels.  56/44 distribution.  Moving the battery as I’m doing here results in 1090 lbs. over the front wheels and 960 over the rear.  That changes the distribution to right at 53/47.

Picked up an $11 box from Walmart.

It became evident pretty quickly that the trunk/opening is so small that if I bolted the box base down, I wouldn’t have room to actually get the battery in the box.  So I had to section the box and install some ‘guides’ that help align the upper part of the box with the base.

Turns out that there’s a horizontal uni-body “beam” that runs across the back of the car – it’s where the rear leaf spring shackle attaches.  Had to mount the base so the bolts hit in front of and behind that beam.

I was able to re-use the ground cable – checked resistance on it (1/0 cable) and showed a 0.00V on the volt meter.  So I cleaned off a captured nut right behind the battery that helps mount the bumper.  Removed the paint from all surfaces and bolted it up.  Checked resistance through the body from the ground in the back to the engine block/chassis ground in the front — 0.1 ohm.  So I think I got a good ground in the back.

I may yet drill two more holes through the trunk floor and the box base and fashion a battery tie-down as well.  A wise choice I think given that what structural integrity the box had is now gone.
Ordered my cables through Amazon — 2/0 gauge for the starter and 4 gauge for the 12V+ electrical distribution terminal on the driver’s side inner fender.  The alternator output also goes to the same distribution terminal.  This arrangement results in the starter being on it’s own dedicated 12V+ cable.  Looks like each will be around 150″ long.  
Here’s the made up lug on the 4 gauge.  Process for making up the lug described further down.

I stripped about an inch of insulation off the end of the cables.  Apply flux liberally to the end of the cable and inside the lug.  Then cut small pieces of solder and drop them into the bottom of the lug.

Next, insert the cable and using a large pair of crimping pliers, crimp the lug onto the cable.  Now you’re ready to let the lug hang down by gently closing the vice jaws on the cable/insulation.  Put your torch on the lug and as you heat it, the solder gets drawn up into the cable strands.  Then, apply just a bit more solder around the lip of the lug.

I used shrink sleeve to finish off the 4 gauge.  Unfortunately, I didn’t have large enough shrink sleeve to go around the 2/0 cable – which gives you an idea just how big that stuff is.  I cut a piece of the insulation I removed and used it to close the gap between the existing insulation and the back of the lug.  Then used electrical tape to cover all that.  Last a few tie-wraps to be sure the tape doesn’t come loose.

Routing battery cables from front to back is a pain.  This is the third time I’ve done it on various cars.  I hope it’s the last.  The car had a fuel return line and an emissions charcoal canister line that were no longer being utilized.  So I removed them – that made room to run the cables along with the hard lines for fuel and rear brakes.  Figured that OEM location was one of the safest places I could put them short of running them through the interior of the car.  The cables run from the starter stud and the electrical distribution stud on the passenger side across firewall behind the valve cover and then turn down and run under the car.  Sans lift, impossible to get a shot showing the whole routing — but a couple of shots of the little OEM metal fingers that bend into place holding the cables and fuel/brake line.

Couple of shots here of where we pass through into the trunk.  Two separate holes for the cables.  Since we’re in coronavirus lockdown, I had to make grommets out of left over heater hose.  The pic below you’re looking straight up over the rear axle.  The dark line you see to the left cutting off the corner of the picture is the passenger side rear damper.  It is mounted dead vertically from over the leaf spring straight up into the unibody.  The cables come out just inside of it – second/smaller cable is above the the larger one, obscured by the shadow.

I had to fab a new “u” strap for the battery terminal because of some much cable in the 2/0 and 4 gauge.

Given all the black carpet in the trunk, when I get it all back together, you’ll barely be able to see the cables — just the box back there.

Cut/threaded some bits for a tie-down strap.  Had to run it length-wise to avoid the unibody crossmember below the battery (see picture further up).

All done — pretty happy with the way it came out.

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