Dual to single battery change in early 911

Here’s how I resolved the battery problem in my 70 911E.

One original battery was going to cost me $86 for a 36 amp/hour battery!

STINGER BATTERY: I hunted around for a Stinger dry cell battery for some time but was unable to find one in the Sarasota area of Florida. I liked the idea of the Stinger because it would fit into one of the twin battery boxes. I could have ordered one locally but it was going to cost over $200 delivered and I wasn’t keen on the distributor who was more interested in fleecing kids out of thousands of dollars for mammoth stereo systems and big shiny wheels with ultra low profile tires.

VORTEX BATTERY: I finally opted for a single Vortex battery, made by Optima and available at Batteries Plus. About $129 less a 10 per cent discount coupon from their website. Comes with a two year replacement guarantee followed by another four years of pro rated coverage. Basically $20 a year which is about what regular auto batteries seem to cost anyway.

I would really have liked to install the single battery on the right side of the car but there was not enough room with the spare wheel. I put it in the front left side with the negative terminal innermost in the box and the terminals facing the rear. The battery has a removable base which I left on to make it fit tighter in the compartment. About two thirds of the battery goes in the box leaving 3" to 4" exposed.

To hold it in place I used a piece of 1/8" x 1" aluminum bar about 8" long which I happened to have around. I drilled a hole at one end to bolt onto the stud which holds the ground strap. Using a vice I bent it out below the hole to meet the edge of the battery then bent it down to hold the battery in place. Made a few minor bending adjustments to make it fit snug then covered it with a piece of bicycle tire inner tube to protect the battery.

I removed the positive terminal from the wire to the right side battery box and insulated the end with innertube and electrical tape.

The battery works great, turns over the engine really quickly and it isn’t going to mess up those battery boxes which I hope I have cleaned and painted for the last time.


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Allan Broadribb
'72-911E, 2.2l with Webers

I thought about buying two 6 volt dry cell Optimas (I think they are smaller) and wiring them in series for 12 volts. Instead I bought the 12 volt and put it into my smugglers compartment. (I don't have A/C) It saved me 10 pounds and removed a great deal of battery cable. ( about 5 feet) I have the big late model gas tank for my weight ballast up front, so no problems there.

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Tyson Schmidt
72 911 Cabriolet

I recently put an Optima in the left side box, on its side, and used the Automotion battery strap & ground cable kit. Painless and quick install (well, painless except for the $$).

I installed an Optima battery about 3 months ago. It installs into my '86 with an adapter that is bolted to the bottom of the battery (you can buy it from AJS in San Diego). Car starts faster and no more problems with the aforementioned leaky battery.