Battery - Going from 2 to 1

[JimNB]

Can someone describe the process of going to 1 battery from the stock 2 ?

Is it simply a matter of running the "live cable" from the passenger side to where the single battery will be (on the driver's side) or is there more to it than that ?

Thanks.

[Tyson Schmidt]

Simple. Just take out the passenger side battery and the cable that runs around the back of the gas tank from the drivers battery to the passengers battery.

Oh, and of course, use a full-size single battery. Might I suggest an Optima? No acid leaks!

[JimNB]

It seemed that simple when I looked at it but so far, nothing on this project has been this simple !!

Can you recommend a specific model of the Optima ??

[tight as a bull's ass]

I have a 1 battery setup in my 1970T but it's not really a full size one.

A full size would be better, though. Starting power is a bit weak on these cold days.

[Tyson Schmidt]

I think I've got the 800 (red top) in my '72. I installed it into my smugglers trunk. I like it there due to its more central location both left/right and fore/aft. It's behind the front wheels, and closer to being centered.

If you are going to put it in the left front, you might get the Stinger gel-cell battery like Jack Olsen has in his car. It's smaller and lighter. Check out his website. I think it shows the install, if I remember correctly.

[marc weintraub]

I was going to go with the Optima in my 72 and 73, but I decided against it because of it's size. I went with the sealed Stinger battery. Same spec as the Optima, but smaller and fits directly into the stock battery box.

[Joe911]

Going through the same process - deciding on which battery. The Optima is too big for the battery box. Summitt Racing also has a Pro-Volt 1100 amps that is 7 3/4 x 6 1/2 x 6 3/4 which would fit great and is 119.95. Probably others available locally - see your local auto stereo installers.

[304065]

First, if you remove the starboard battery, make sure you remove the cable-- I have heard of folks just taping it off which means that there's a hot lead just waiting to spark to the body sheetmetal on top of the fuel tank, giving new meaning to the phrase "ignition points."

The Optima battery does NOT fit properly in the stock battery box. To get it in, you will have to slide it in sideways, with the terminals facing to the rear, and find some way of securing it. Elsewhere on this board there's a picture of someone who has done that, but IMHO it puts the positive terminal too close to the sheetmetal. . .see above.

So I have a Stinger, which I got for $200 from a car stereo shop in florida- www.sounddomain.com, and it will easily fit in the stock box, only caveat here is man is it HEAVY.

My plan is to relocate the battery to the smuggler's box- don't waste your after-tax dollars on Summit's plastic battery relocation box- it won't fit down there. I'm going to fab a base to hold the stinger out of angle iron, and some kind of bracket to hold it down. Tyson, I would be interested in the details of your install in the box if you have a few moments.

[pwd72s]

Only one suggestion to add to the above excellent ones. Be sure to keep all your old battery mounting bits and pieces, plus maybe consider leaving the old cable in place, insulate the ends & tuck them out of the way? I merely folded mine back alongside the tank when I did my optima experiment..NO WAY either end could reach a battery, therefore no spark worries. That way, should you ever decide to return to stock, it would be easy to do. Which is what I did once I discovered that Sonnenschein, a german battery maker, makes an exact size replacement for the twin batteries, but gel cell. $pendy little mommas, but I get around 7 years from a set...Think I'll also be looking at stinger when it's replacement time. I've run totally sealed batteries for years, will NEVER return to the old lead/acid style...just the peace of mind of no liquid acid sloshing around up front is worth the price of admission for me.

[jriera]

Just replaced the two-battery with an Optima 800 last weekend, some experiences...

I decide to put the Optima on the drivers side, flat on the side, terminals to the rear (facing the driver) of the car, I find out that two heavy duty springs and the original battery mounting hardware works very well to hold the battery from a side-to-side movement. To avoid front-to-rear movement I have use two pieces of wood (don't remember size) and not-so-gently used a hammer to wedge them in place between the battery and the battery box.. I need to find a better support.

I disconnected the passenger side battery terminal (and ground terminal) and tucked away between the fuel compartement and the spare tire I also located and disconnected the cable (positive) that goes from the passenger side battery to the driver side, tucked away between the fuel compartment and the spare.. both ends of the cable isolated.. you will need a new ground cable for the battery (existing one will be too short) I installed a #1 cable from Pep-Boys..

Hope this helps.

Jordi Riera
73.5 911T Targa
Richardson, TX

[Phoenix]

pwd72s : Which model Sonnenschein batteries did you install? I'm thinking of a similar set-up for my '73.

[katigbr]

Good Timing. I'm also doing the same mod. I'm moving to a single Optima into the smugglers boot. Had I known about the smaller Stinger that fits the standard box I would have gone with that.

One question that I've got is how do I safely connect the positive terminals together, securely. This is the connection required to route the positive from the new location to the old cables/wires in the old location. I could just bolt them together and insulate the connection. Is there a better way?

Additionally, some aftermarket components have fused links located near the old battery. Should I relocate these near the new battery location? I believe this is done to prevent electrical fires due to shorted wires overheating. I think that the fused links are supposed to be as close to the battery as possible.

Thanks all.

Rick

[Rob Markworth]

This may be a dumb question, but why would you want to switch to one battery? Is it a matter of fitting a more powerful battery? I just purchased a '73 E that has been converted to one, and I have been thinking about converting back to two. It seems to me that there would be better weight disstribution, and the front compartment would be much cleaner looking with the batteries in the boxes. The one battery is located in the front on the driver's side, and does not seem all that stable.

Rob Markworth

[72SMFI]

I am thinking we need a tek article one putting a stinger in the passenger side batt box. Or a gel cell somthing light in the side without the driver. Why put the battery on the driver side that is to easy! For better wieght distribution it NEEDS to be on the passenger side!!!

[911pcars]

Some thoughts on the battery placement/brand issue.

Use some type of sealed battery in your Porsche. You don't want to mix sulpheric acid with sheet metal.

The Optima red top battery is a good replacement as it is sealed and has a rating of 800 CCA's. The wimpy and expensive factory batteries are .... well wimpy and expensive as well as regular, sheet metal-eating lead acid types.

$200 for a Stinger? Egads. IMHO, that's a lot of dinero to spend on a battery (even a sealed one). Others report it's lighter than the Optima (which I weight in at 35 lbs.), but John_Cramer says the Stinger is heavy. I know heaviness is relative. Just for comparison,what's it weigh? However, there are race-type, lightweight sealed batteries that cost much more but with matching, light-weight cold-cranking specs.

There are 5 positions to install the Optima. Each of the following has an issue with the cable attachment and battery post access.
Driver's side w/posts facing front
Driver's side w/posts facing rear
Passenger side w/posts facing front
Passenger side w/posts facing rear
Smuggler's box

I vote for whichever position is most accessible to disconnect the ground cable since one should remove the negative cable first when disconnecting the battery (for safety). On the driver's side, the ground post is on the top left corner when the battery faces toward the front. For equal access, the battery posts face the rear for a passenger side install.

The factory, so it is said, placed two batteries in the outermost corners to help distribute the weight. The two batteries replaced a single battery and lead weights in the front bumpers in the very early 911s. Apparently, two batteries costs less than a single battery and 50 pounds of lead.

The passenger side sounds like a good weight distribution compromise for a single battery in our LHD 911s. Either that or two batteries and a permanent passenger for optimum weight distribution.

The smuggler's box is a good location in a track-only car that has had the battery boxes deleted and trunk space taken up by a fuel cell.

Secure the battery and make sure the positive post won't ever accidently touch ground (metal chassis). Same goes with the unused positive cable. The cables are wired in parallel so it doesn't matter if the battery is installed between the Webers. If the + cable accidently touches ground, it'll create enough heat to weld metal and/or cause a fire. A fire near your fuel supply is not good for resale value.

The method of securing/mounting Optima batteries is as diverse as our audience here. Someone should collect the many mounting strategies for prosperity. I'll try to record mine and post it when this subject comes up again next week or this Friday.

That's about it for now,
Sherwood Lee
http://members.rennlist.org/911pcars

[Jack Olsen]

The Stinger SP800 is 5” H x 6-9/16” W x 6-7/8” D and weighs 24.9 pounds, which is 12 less than the Optima. It has a 10-12 year life expectancy, and 800 cold cranking amps. I think you can get them for $172, which -- admittedly -- is a lot for a battery.

But it's smaller, lighter, more powerful -- and more expensive -- than the competition. Sounds just like a 911.

Specs: http://www.stingerelectronics.com/sting_products/batteries.asp

[roGERK]

I'm with Rob on this one.

The early 911s have two batteries as far forward as possible and one on each side for a reason - to give better weight distribution.

Before the two batteries were introduced, 911s suffered the ignomy of having "bumper reinforcements." These were nothing more than shaped lumps of pig iron glued into each corner of the bumper. Their role was exactly the same as the batteries; to get weight as far forward as possible and as far on each side as possible.

The post 1973 cars have a single battery, but the areodynamics are better, and there's the big bumper at the front.

Keeping two batteries but upgrading to the Stinger (which apparently fits into the battery box) seems a sensible modification; going from two batteries to one seems less so - the factory spent a lot of time and money trying to "tame" the handling of early 911s - they didn't bother to locate and wire two batteries just on a whim!

There's also a reliability bonus - since modern batteries are quite powerful and one is quite capable of cranking a 911, having two batteries gives the car lots of cold starting power - no bad thing at any time and especially the winter.

Free advice, worth every penny from...

- roGER

[RPMClassic]

I am with jack on this one. I am running dual stingers in the stock location and couldn't be happier. It is a mere 12 degrees out today and the car turns over with the touch of the key. I will go so far as to say, that after I got over the initial shock of purchase price, these are hands down the best investment I have made into my car.

Good luck with your battery replacement.

Jim

[911pcars]

Jim,
One look at your hood and I know why you're running two 800 CCA batteries. What kind of alternator are you using? Does it keep up with the electrons?

Sherwood Lee
BTW, I meant to say prosterity, not prosperity. Never mind.

[RPMClassic]

Sherwood -

Well after ripping through a few rebuilt bosch units ( and never finding one that lasted very long ) I decided one day to lay down dead and buy a new Valeo unit. It did require me to update the fan housing and the air snorkle on the back of the unit - both of which are ridiculous in price but readily available.

Its good piece of mind to have this all sorted out - as I take frequent road trips and drive the car alot. The added bonus of finally being able to clean and powdercoat all the annoying sheet metal during the install process gave me a few nights of sound sleep and a pat on the shoulder!

We are taking the car ice racing next weekend and plan on using the lights ALOT. We keep you posted of any electrical failures.