How to easily fit a modern battery in a classic car

Photography by Carl Heideman • Lead by David S. Wallens

[Editor's Note: This article originally appeared in the September 2007 issue of Classic Motorsports.]

Sometimes our classic cars don’t keep up well with modern times. While a lot of specific replacement parts like body panels, interior bits and trim pieces continue to be available in quality reproduction form, other more common wear-item needs like tires and batteries are, ironically, getting harder to find in the sizes we need.

Batteries can especially be a problem, as the sizes required by our classics are often no longer produced. Thanks to new battery sizes, many classic cars lack a properly fitting tie-down strap. As a result, many of them are running around with batteries that aren’t strapped down at all. 

This is downright dangerous—every battery should be properly secured. An unsecured one can come loose and short out, risking fire or explosion.

Installing a new battery into a classic doesn’t have to be hard. We recently fitted a new battery to our 1967 Jaguar XKE. When we got the replacement battery, it was the same length and width as the old battery; however, the new one was about two inches shorter. As a result, the factory battery hold-down would no longer fit. 

Since our car is not a concours queen that needs to remain 100 percent original, we quickly fabricated a safe and secure strap to hold the battery in place. Call this a quick way to make sure we’d be enjoying the XKE for years to come. 

While our strap would only fit a similar XKE, the procedure we used would apply to many other cars. It’s something you can easily do at home in an afternoon with only common hand tools.

Step 1.

Our original hold-down would no longer fit our new battery, which is about two inches shorter than the original piece.

Step 2.

We realized that we could quickly fabricate a simple steel strap to secure the battery. We took a few measurements to get a ballpark length.

Step 3.

Next we cut some 1/8x1-inch hot-rolled steel strap. The piece needed to be 14 inches long. We’ve found this type of steel strap to be the perfect material for battery mounts. It’s sturdy enough to do the job, but easy to work with.

Step 4.

We had to bend the ends to meet the mounting locations, so we used a five-pound sledge hammer and a vise.

Step 5.

After test fitting the strap and looking for good mounting holes to use, we realized that we needed to reorient one end 90 degrees. Again, we were able to bend it in our vise.

Step 6.

We then drilled holes in each end of the strap.

Step 7.

We tried to avoid drilling holes in our XKE. In the front, we used an existing bolt and hole (arrow 1) to hold the strap. Note the lug for the original battery hold-down’s J-bolt (arrow 2).

Step 8.

We did have to drill a new hole at the other end of our XKE. We chose to drill into another bracket rather than the body of the car itself.

Step 9.

We test fitted the new strap and found we had to do some trimming on one end. We did so with a grinder. Then we gave the strap a coat of silver paint in preparation for installation. We made sure the battery was unable to move; if the terminals came in contact with the strap it could cause a major short circuit.

Step 10.

Once installed, the strap held the battery safely in place while keeping it very serviceable.

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Comments
dug
dug
9/9/20 3:53 p.m.

Question,

What prevented you from just shortening the bolts or having new one made to adapt the lower profile battery in this case? 

 

Dug

David S. Wallens
David S. Wallens Editorial Director
9/27/22 2:18 p.m.

True, behind-the-scenes story: The lead photo was taken on my desk. laugh

wspohn
wspohn SuperDork
9/28/22 11:40 a.m.

Some classics are easy to retrofit and some aren't.

The Triumphs are easy - big box under the bonnet at the back of the engine compartment = 5 minute change time.

My MGs are a bit harder - they used twin 6V under the car. easy solution, replace with single small 12V - simple plywood spacer to space it up above the angle iron stock cradle, plus a simple hold down kit to keep it in place.

At the other end of the difficulty spectrum is my Solstice GXP coupe - remove front fender to access battery buried down low under the firewall. Anyone got one with even harder to change battery?

David S. Wallens
David S. Wallens Editorial Director
10/3/22 2:18 p.m.

In reply to wspohn :

I didn't know that about the GXP coupe. Sounds, um, fun.

Just putting this here in case it helps anyone: how to fit an Optima battery into a Porsche 911.

bosswrench
bosswrench New Reader
12/21/22 5:24 p.m.

Some battery problems are factory-generated. THe once-popular Porsche 914 battery was installed ON TOP OF THE ECU! The chosen place is almost inaccessible, at the left rear corrner of the front of the engine, accessible only from the underside AFTER the battery is pulled from the top, I believe (My 1974 914 went away in the last century so details are hazy).

And even grade school kids know that corrosive fluids come out of  car batteries....  Predictably, some factory ECUs look like garbage-dump rejects by the time the owners notice the problem. Structural attacks on the subframe rails also abound on neglected examples.

wspohn
wspohn SuperDork
12/22/22 10:28 a.m.

BTW - nice MGA Twin Cam in the background (I have a couple of those). Their batteries were twin 6V, one on either side of the prop shaft in front of the rear axle.  Almost always converted to a single 12 V that requires only small mods to fit.

OJR
OJR New Reader
5/14/23 1:31 p.m.

It's been a long time but I seem to remember the 88 BMW 750 had 2 batteries under the power back seat.

porschenut
porschenut HalfDork
5/16/23 8:27 a.m.
bosswrench said:

Some battery problems are factory-generated. THe once-popular Porsche 914 battery was installed ON TOP OF THE ECU! The chosen place is almost inaccessible, at the left rear corrner of the front of the engine, accessible only from the underside AFTER the battery is pulled from the top, I believe (My 1974 914 went away in the last century so details are hazy).

And even grade school kids know that corrosive fluids come out of  car batteries....  Predictably, some factory ECUs look like garbage-dump rejects by the time the owners notice the problem. Structural attacks on the subframe rails also abound on neglected examples.

Sorry but your memory is wrong.  Battery is on the passenger side, over the fuel pump right under the gap between the engine cover and body.  The stock battery had a cover to keep rain water off it, but everyone lost that so water doused the battery and the acid-y solution dripped on the fuel pump and lines causing fires when fuel leaked on the heat exchangers which were nearby.  The ECU is on the driver side.

porschenut
porschenut HalfDork
5/16/23 8:29 a.m.

The easy button for most is a prius agm battery which is very small and can mount sideways or even upside down.  The challenge there is the durn battery posts which are too small for normal stuff.

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