Only One Battery

[grizzfan]

Hello again!

Still examining my recent purchase and looking under the hood I notice there is only one 12v battery, this one on the driver's side; where the other one was is the positive cable wrapped in a baggie.

The car cranks great and fires right up. But why would someone want to do this? Are their any potential problems with this arrangement?

Thanks

[zippy_gg]

What year is your car?

[dicklague]

The batteries are hooked up in parallel. They were put out there in the front corners for weight and balance. Porshe felt the cars of that era needed weight at the far front corners and they did need it for sure.

The car will run on one battery with no damage. Just be sure to keep the other battery leads isolated. Or at least the positive one isolated from chassis ground.

my 1973 has one battery right now and has had one hooked up for a while. The passenger side battery is will not hold a charge so it is disconnected and just riding along as ballast.

[HarryD]

What ype of battery do you have. It is one o fhte small ones that fits in the box or a larger one that is outside the box?

I any case, you may or may not need the cranking power. Ther are several options. One is to install the second pattery, or put one larger one in. Many of us, me included, put a single Optima in our car to prevent acid corrosion ofthe body (and the suspension pickup points).

When I did this, I disconnected the cable to the passenger side battery by removing it from the driver side positive battery clamp.

This thread should be helpful and has links to other threads with yet more information.

early 911 replacement batteries

[grizzfan]

It's a 1973 911T.

I understand the weight distribution issue and glad it will run OK on one. The baggie on the other battery's cable seems a bit short on protection so I'll beef that up. I need to do some more probing as I don't see a battery box and don't like that.

[grizzfan]

Thanks HarryD, et al.

tpr

[Christien]

I think every early 911 I've seen has been converted to single battery. My understanding is that it's done because of the difficulty in sourcing 6 volt batteries.

[brads911sc]

They used 2 12 volt batteries wired in parallel, not 6 volt batteries.

Originally Posted by Christien

I think every early 911 I've seen has been converted to single battery. My understanding is that it's done because of the difficulty in sourcing 6 volt batteries.

[HarryD]

Originally Posted by grizzfan

It's a 1973 911T.

I understand the weight distribution issue and glad it will run OK on one. The baggie on the other battery's cable seems a bit short on protection so I'll beef that up. I need to do some more probing as I don't see a battery box and don't like that.

Don't fret too much about the weight balance thing. To my way of thinking, unless you are someone like Michael Schumaker, I doubt you will tell the difference. I know I don't.

Please post a shot of your trunk (full) and the battery area. Please pull the carpet back so we can see the fuel tank and sheet metal.

This is an exceptionally clean trunk but you can see the driver side battery box on the mid right hand side:



Thanks m1franck

Over at the Early 911S BBS (Early 911S Registry Bulletin Board - Powered by vBulletin), there are a number of folks very knowledgeable about the pre-73 cars.

Here are a few battery pictures from there:

Driver side battery. Note the two very thick cables from the positive post (in front). One goes to the rear of the car to power the starter and the other goes to the passenger side battery. The battery clamp is screwed together and you can loosen the screws to remove the un-needed cable.



Thanks Alan.UK

Passenger Side Battery:



Thanks NickP

[grizzfan]

Good Lord, after looking at your trunk, I'm almost embarassed to show you a photo of mine!! I'll do that however. My battery is not in that well or box at all, just positioned to the left of the well and bumped up against what looks like a gizmo (evaporator?) for the fuel line.

[HarryD]

Sir, those are not my pictures. They came from some folks who are much neater than I.

Heres a shot of part of my trunk to give you an idea of the mess I have up front:

[grizzfan]

HarryD,

I mistakenly placed the trunk area photos in the "No Holes for the Pully Wrench" section.

Sorry.

[dicklague]

I could post photos of my trunk now too!

[Roc Doc]

Originally Posted by HarryD

Sir, those are not my pictures. They came from some folks who are much neater than I.

Heres a shot of part of my trunk to give you an idea of the mess I have up front:

That light duty plumbers strap scares me. Do yourself a big favor and get a proper mounting kit. In an accident, that thing would not hold the battery in place.

[80-911SC]

let me take a guess no PPI correct ??

[HarryD]

Originally Posted by grizzfan

HarryD,

Per your request here are 7 shots of the trunk area. The carpet in the trunk is very deteriorated and I just pull it out. The hood support is missing and the former owner was using a broom handle. (I'll start looking for one of those someday too.)

On one of the last shots I pulled the canaster away from the battery. Didn't see one in your photos and I really don't know what it is.

I see the makings of rust in the very forward part of the trunk. I'll treat that with some baking soda shortly. I see no evidence of a cross-over battery cable.

Grizz (until you tell us your real name):

Thanks for the shots.

Your trunk looks Wayyyyy better than mine.

This is what I see:

The big black thing is a carbon canister for your gasoline fume collection system. You do not want to take that out.

Like I said, one of the big black wires on your battery positive post goes to the disconnected wire on the other side. Tug on them and one of them will cause the other end in the trunk to move. Disconnect it from the battery clamp.

The rust you are referring to does not look bad and once you are sure it is neutralized, I would spray it with Extend and top coat it with some Satin Black paint.

You should fabricate a hold down for the battery. If you look in the back of the battery box, there should be a clip in the middle of the back wall. You can slip something over that and then run a piece of metal or a cord to the front. If you look in the floor of the trunck near your battery, you should find a captive nut that you can use as the front attachment point. You may also be able to locate a factory hold down but I think the dimensions of your battery may not be the same and that may not work.

While I appreciate Roc Doc's concern, the strap is more stout that it appears. This set up has been autocrossed many times with no evidence of imminent failure. The back side has a small D-ring connected to the strap. The front of the strap is bent over the battery and fastened to the floor of the trunk with a bolt to the captive nut in the floor.

You need to put something over your positive terminal to insulate it so if you accidentally drop a piece of metal you don't get a giant arc (did you know you can stick weld with a car battery?)

Lot of us use a pole (or hockey stick) to hold up our hoods. You can get replacement gas shocks or other options. Check the Pelican Catalog. In our cars, the hood shocks are not that hard to get to and mine have been in service for about 6 years now with no problems.

[grizzfan]

HarryD et al,

Thanks for the very thorough suggestions and comments concerning both my battery situation and pully wrench questions. As well the remarks about fluids where helpful. I had already decided to do a complete fluid change and recognize some of the recommended lubricants from other readings.

I promise; I'll be back!!!

Tom (aka Grizzfan - I'm a University of Montana Grizzly Football savant!)

[HarryD]

Tom:

Glad to help out. While we can get overwhelming, the reality, as I see it is the the cars are generally well engineered and easy to work on once you understand how they did it inthe factory.

I see Grady Clay posted on your other thread. He has forgotten more than most of us will ever know.

[Oldporsche]

I have often thought that the factory might have planned for the early two battery cars to use 6 volt batteries in series. The reasoning has come from the fact that the 12 volt batteries used by these cars are the same size as the 6 volt batteries that were available at that time. The wiring could have been easily done that way.

Often owners used a single VW battery which was size 42. This was an adequate battery for this use. I made mine work on the passenger side to offset the wt of the driver. The negative post was connected first and that end went into the battery box first.

Some of the real early SWB cars actually had lead weights behind the front bumper.

Yes, Grady Clay has certainly forgotten more about these cars than most will ever know.