Batteries for an Early 911?

sfierle · 08-25-2003, 06:40 AM

First let me start by saying, I just discovered that the PO used lawn tractor batteries when he replaced them last time. I was quite suprised to see, after having start-up problems, that after looking at the batteries, they read "Lawn and Garden". After gaining my composure (major chuckles), I realize these probably were not powerful enough. My question for you folks, what should I do? What kind should I buy that are reasonably priced? Should I just go with a single large battery and place it in the middle (my previous one had it this way)? I want good starting power, and want to keep it as cheap as possible (I have other projects for this car half done).

Thanks

RallyJon · 08-25-2003, 06:42 AM

Here's what I did:
http://www.rallystuff.com/pcar_electrical.html

trade14u · 08-25-2003, 06:53 AM

I just had the same dilemma and opted for the single battery conversion. The good news is, there are numerous batteries with good starting capacity that will fit INSIDE the battery box.

I went to Sam's Club and bought an Exide battery for 29.00 (most people here suggest the Optima batteries but I was doing this on the cheap) that is about 525 CCA. When I went, I brought my u91150 (whatever they're called) inside the store to compare/measure the size. The battery slides right into the box with the posts sticking out.

The single battery conversion was very easy:

I put my new battery on the drivers side. I followed the positive lead from the passenger battery to the driver's side positive connector (they are both connected here) and disconnected it. This takes away the 'parallel' configuration of the two batteries. I left the wire there but removed the connectors and taped the ends up (in case you ever want to revert to the two battery set up). THe negative lead on the passenger side unscrews from the wall. That's it. EZ.

$29 Exide vs $77/each for two Interstate U911-50s or $100 for an Optima. Your choice. I'm El Cheapo.

Brad

Chuck Moreland · 08-25-2003, 07:07 AM

The Odyssey PC1200 fits the box and even uses the factory tie down strap:

It has plenty of power as a single battery. The smaller Odysseys also have the power but will not fit the factory strap without modification.

David E. Clark · 08-25-2003, 08:32 AM

Quote:

Originally posted by Chuck Moreland
The Odyssey PC1200 fits the box and even uses the factory tie down strap:

I use the Odyssey as well. It works great with plenty of power -- even more power than the two factory batteries. I didn't have to lay mine on its side. It fit just right in the traditional position with a piece of 1 inch styrofoam behind it. Bought mine from JEGS. They had the best price I could find and a free shipping offer.

http://www.jegs.com/

pwd72s · 08-25-2003, 09:02 AM

If you're into originality, Sonnenschien, a German battery manufacturer, makes a gel cell that is the exact same size as the original batteries. I'm quite pleased with my pair, but they are $uper $pendy. If memory serves, they ran around $350 the pair.

GRMPer · GRMPer's Garage

I used a single Optima on the passenger side, helping corner weights. It too fits using the stock straps (just barely)

Per

JSDSKI · 10:20 AM

Interstate makes the little ones that match the factory location. Been working in my 72T for about a year now with zero issues.

On the other hand, have you considered doing a replica of the extremely rare "John Deere RS" - green with yellow side graphics is the only way to go. You haven't lived until you've seen "John Deere" in the dropped down RS Carrera graphic style.

jmohn · jmohn's Garage

Don't laugh too hard at the PO's use of a "Lawn and Garden" battery, he may have used them on purpose as they are often designed and rated for "rough service", meaning they will withstand more vibraton and jarring than a normal car battery. Of course you must choose batteries of sufficient capacity.

Jerry M
'78 SC

Paul Valcourt · 10:48 AM

On my 73 I took the dimensions of the original batteries went to Sears and bought a pair of 650cca (cold cranking amps) dual post batteries that were the same size. Then i cut off the top posts and screwed on the side post conversion posts. They fit and worked great with a combined 1300cca starting was no problem. I think the batteries were about $75 each (CDN).

dad911 · 08-25-2003, 10:39 AM

Quote:

Originally posted by trade14u

$29 Exide vs $77/each for two Interstate U911-50s or $100 for an Optima. Your choice. I'm El Cheapo.

Brad

My Optima is at least six years old. My last Interstate lasted two years. IMO Optima is same or cheaper in the long run.

targa911S · 08-25-2003, 10:39 AM

exact duplicates...interstate mdl # 911-50. $100.00 each. Fit perfect. Been crankin for 2 years now.

911pcars · 08-25-2003, 11:21 AM

I've been cranking an Optima since '96, albeit not on a daily basis and with a battery tender between running. Seems to only fit on the driver's side with the larger, late model fuel tank. BTW, the shelf life (disconnected) is a lot better than wet-cell lead-acid batteries.

Try to avoid wet cell batteries that accelerate the death rate of the battery compartments/pan.

Sherwood Lee
'69 911
http://members.rennlist.org/911pcars

sfierle · 08-25-2003, 04:53 PM

Thanks for all the input, I knew I could count on you!

SnakeDoc · 10-16-2004, 08:07 PM

Anybody got some step by steps for how to convert to single battery optima? It sounds like the thing to do, if it will fit the passenger side battery well.

Tom

copper · copper's Garage

69 T

2 Costco Kirlkland Signature #7's. 640 CCA x 2 = 1280 CCA

$52 CA each = $104
or $80 US.

Fit in the boxes. (Sideways, earthed side in)

Never a problem starting.

Jim

lateapex911 · 10-16-2004, 08:55 PM

The Optima types (Odysey) are the way to go without a doubt!

No acid, any mounting position, one instead of two, and more power! Where's the downside?

Expense?? Not in the long run!

lateapex911 · 10-16-2004, 08:59 PM

Quote:

Originally posted by SnakeDoc
Anybody got some step by steps for how to convert to single battery optima? It sounds like the thing to do, if it will fit the passenger side battery well.

Tom

No instructions needed. Get the Odessy as above.

Wrap the left side connections well and fasten somewhere.

Thats pretty much it!

If you go with the Optima, the fittment is different, on its side, pos side out. might need to mod the strap in some way, but it's pretty obvious.

911pcars · 10-17-2004, 02:08 PM

"If you go with the Optima, the fittment is different, on its side, pos side out. might need to mod the strap in some way, but it's pretty obvious."

...or pos side in. Either way, fabricate a holddown bracket to prevent the battery from shifting and the pos. post from contacting ground.

Sherwood

lateapex911 · 10-17-2004, 02:54 PM

Yeah...I did pos side out as I was considering that in the event of a right front crunch the post could get jammed in the box, short out, and POOF!

And there would be NOTHING you could do at that point to prevent a big ugly meltdown.

It should be noted that I have an RS plastic tank, so the pos post has much less to hit out there. But in either case, get a GOOD cover boot for the pos. post!