Why do early 911's have 2 batteries?

[makaio]

why do the early 911's have 2 batteries? I was just pondering this while I'm trying to figure out what's wrong with my car.

[Formerly Steve Wilkinson]

It was basically a matter of balance, I believe--that two batteries, one on each side, both up front, optimized the weight distribution as ideally as was reasonably possible. It wasn't an electrical boon--there isn't anything intrinsically better, electrically, about two batteries--it was a balance decision. That was in the days when Porsche prided itself on having lightweight, small-engine cars balanced as well as possible within the limitations of the rear-engine configuration. Later "fixes," as the cars got increasingly heavier, more luxurious and more powerful, first took the form of fatter rear tires, then the Weissach axle, etc. The cars of the twin-battery era are looked on by many as the purest 911s. Wish I owned one.

Stephan

[Jack Olsen]

As someone pointed out recently, it was also part of a PR effort, in the face of Ralph Nader's criticism of the Corvair, to calm people's fears about a rear-engine design.

I've never met anyone who honestly felt they could tell a significant handling difference from the two-battery setup, at least when it's converted to a single. That said, I'm sure there are guys out there who would claim the difference is huge.

[GIBSON]

I always thought that the same engineers who decided that placing lead weights in the front bumpers of 1965 911s was a good way to improve handling faults also thought up the twin battery
idea. It probably helped balance somewhat but it gave early non-galvanized cars another place to rust. I've never switched mine over to a single battery, it's easy enough to do however. I did take the lead weights out of the old '65 though.....

[tobluforu]

Early front bumpers were also lead filled on each corner. Another balence issue.

[Early_S_Man]

It was an experiment in weight distribution ... that was two years late! Had it been done at the introduction of the '67 911S, and been combined with a few other weight-saving/redistribution measures ... like the '72 oil tank, and fiberglass hood and fenders, it would have been heralded as an engineering marvel ... compared to the '65/'66 cars without the cast-iron 'bumper reinforcements!' Of course, if the battery boxes had been incorporated into fiberglass fenders immediately below the headlamp buckets ... the effect on handling would have been even better, and the corrosion damage issue in the trunk would have been eliminated,. too! There might never have been the LWB change in '69 if all of their effort had been done early enough, and all oil tanks might be in the 'right' place ...

[9XI]

I don't buy the balance thing. Maybe it was a marketing gimmick. Think about it. The vaunted '73 RS had only one battery -- on the driver's side. You'd think if the balance thing was really that important for the handling, Porsche would have included that feature on its club sport model.

For the record, I took my passenger side battery out and have never had problem one.

[pwd72s]

"I've never met anyone who honestly felt they could tell a significant handling difference from the two-battery setup, at least when it's converted to a single. That said, I'm sure there are guys out there who would claim the difference is huge." -Jack Olsen

Jack...I'll bet that guys named unser, andretti, or fangio could say they can tell the difference. And they might be right. The rest of us? Yeah, we can dream...

[Kurt B]

F@ck Nader. Little communist jerk off.

[Doug Zielke]

Originally posted by GIBSON
........it gave early non-galvanized cars another place to rust.......

Bingo!

[Randy W]

I'm not sure if adding 15-20 lbs to the right front could be easily felt. However, last year I moved my single Optima battery from the left side to the right side beacause I could not obtain a near perfect weight balance from side to side (with my weight in the driver's seat) on my maxed autocross car. When I did this the net effect was easily felt by both myself and my co-driver, especially under aggressive threshold braking.

Porsche in the early years, under the guidance of Ferdinand Piech, was fanatical about "improving" the weight balance issues of the 911: bumper lead weights, twin batteries, aluminum lug nuts, alloy calipers, aluminum decklids, plastic intake manifolds, '72 oil tank, etc. It all seems a bit absurd nowadays with the current luxo-Porsches, but when the 911 was "light", these changes did make a difference, at least on paper.

[Oldporsche]

Porsche used two batteries to frustrate your average battery salesman.

Seriously, warren is right. The idea is for balance, its just a couple of years late. Another thing is this. If you take these two batteries and put them side by each, you would have a big battery and a lot of cranking reserve. So, you actually get a couple of benefits. The ability to move some weight around and get some cranking reserve to boot.

With the products available today to attack rust and prevent crosion, the consequences can be avoided a little easier. (I'm going out immediately and take a look at the '70E this morning)

As far as the comparison with the '73RS as having one battery, I tend to think that the '73RS was is really an early '74 car.

Seriously, if you own one of these cars, its a good idea to keep up on the availability of batteries for this application. This size is not a popular size and manufacturers come and go in the battery game.

Good luck,
David Duffield

[Roland Kunz]

Hello

The Weissach axle came with the 928 and entered the 911 in the 964 bodys

A other benefit from twin batteries is that you can run on one if the other one quits ( and not drining the other down )

About Corvair is to say that they just blowed up a beetle without understanding the backgrounds and limitations.

Now don´t think normal costumers do understand backgrounds and limitations

I know guys who can tell you the actuall tirepressure and tire profile hight while pushing the car at the limits, tehy even can calculate the passenger wight ( also known as "penality wight" under racers ) on the driving feedback.

Grüsse

[Jack Olsen]

...when I did this, the net effect was easily felt...

All modesty aside, Randy, I think a fair assessment of your driving skills and sensitivity would put you squarely in the 'Unser, Andretti, or Fangio' camp.