How to build a battery mount fit for a race car

Update by Tim Suddard to the Elva Mk VI project car
Dec 17, 2024 | Elva, Restoration, Elva Mk VI

Every car needs a battery, and our Elva was no exception. There was no evidence left as to where the battery had been mounted on our car, so we had to go it alone on this decision.

When mounting anything on a race car (or on a performance street car for that matter) the goal is to make everything as light as possible, keep it towards the center of the car (unless you are moving things around for balance), and keep it low in the chassis.

While it might have made some sense to move the battery to the front of the car, that would have meant much longer battery cables to run to the rear-mounted engine.

We had some safety concerns as well: In the case of an accident, the last thing you need is a broken, leaking battery flying towards the driver.

We first decided to mount the battery under the passenger seat. This would balance the weight of the driver, keep the battery low and keep the cables very short.

Short cables not only weigh less but have less resistance. It takes a bigger battery to start a car with a 20-foot-long cable over a short cable.

Once we dove deeper, we realized there wasn’t enough room beneath the seat. This area was largely occupied by the scoop we planned to fit to direct air towards oil cooler.

So we broke out the tape measure and the cardboard templates–just couldn’t make it work. (Remember that this is a right-hand-drive car, hence the passenger seat is on the left.)

We decided to move our fire suppression system–the same system that we had already mounted beneath the driver’s seat–to a spot between the two seats. This would now leave us clear to mount our battery under the driver seat.

Sanctioning body rules are a bit ambiguous when it comes to battery mounting. Again, we spoke to Jack Woehrle, technical director for HSR.

He felt that a standard lead acid battery should be mounted in a container to prevent any leakage. Jack told us that an AGM (absorbed mat technology) would be okay to mount without a container as they do not leak. He felt that a mounting location behind or under the driver’s seat would also add safety, as the likelihood of any battery acid coming in contact with the driver would be reduced.

We did a bit of research and decided that a Motobatt MBTX30U battery would meet our needs. This is a common Harley-Davidson AGM motorcycle battery, so it’s designed to start a higher-compression engine. This battery weighs about 22 pounds, has 450 cold cranking amps, and is small at about 5x6x6 inches. It’s also very common, so if we need one while at a race track, we should have no issues.

Our thought was that if we mounted it under the seat, the battery cable would be less than 2 feet in length–should be plenty adequate for race car use where starting is an occasional event and air conditioning, stereos and other power-robbing accessories are minimal.



To mount the battery, we first built a cage that it could sit in. We welded together piece of lightweight, slotted angle steel and purposely made the box a quarter-inch larger than the battery. Our thinking was if we lost a battery at the track and couldn’t find the exact same one, we had a little space should the sizes vary a bit for this style of battery. We’d mount this box so it sits no lower than the floor of the car.

We then built tie-downs on both sides of the cage out of 1/8-inch steel shaped in a slight “L”. These were again made from scrap we had picked up. We tied the battery down on either side, rather than front to back, as we only had about a 3/4-inch gap between the battery and the seat.

We welded a 5/16-inch, coarse-thread nut onto the bottom of this tie-down nut and then inserted and welded a piece of threaded rod to this nut. We wanted to avoid any slippage and make battery changes easier.

We found a piece of ¾-inch aluminum channel (at Lowe’s) that seemed suitable. We cut it to the correct length and drilled holes at each end to run the threaded rod through. We finished this off with a Nyloc nut to avoid loosening.

Our final step was to weld an “L” bracket to the frame, right next to the battery. We welded another piece of that threaded rod and allowed the rod to stick out into the engine compartment and into the passenger compartment.

Because we did this, we could bolt the ground strap onto the engine compartment side and the negative terminal of the battery to the other side in the passenger compartment.



Overall, we were pretty pleased with this mounting decision, and should we be able to still see the battery when the interior is in place. We may paint it black to make it less visible and cheat a little bit when we enter concours events....maybe cover it up slightly with one of my wifes best table cloths to hide it. Race cars did not have brightly painted batteries in the early ’60s. Considering what the chewed up battery box looked like when done, maybe we should have bought a real battery box instead of the POS that we made with all the botched and chewed up welding......but enough bondo might fix it up just fine.