Battery for 69 911 E

[69porsche]

Gents,
My 1969 911E takes two batteries one on each side for those not familiar with the dual battery set up. Currently I have interstate batteries (x2) in them with 330 CCA. ...Question 1)Interested to know what battery brand name and anything significant you have in your car-talking to those who had or have 911's with the factory dual battery set up. The batteries I am using have the terminal post on top and they just are able to fit in the battery compartments in the wheel well. I just bought the batteries and they are showing just under 12volts, so they are not getting any power to my car. I bought a ...Question 2)CTEK battery charger that should arrive tomorrow(your thoughts) and get the batteries charged, but it does not remedy either a bad alternator or a parasitic electric drain. I am thinking once I get the car charged to have the... Question 3) quick battery cut off knobs that when turned, it can shut or turn the power on-they can be bought at any local auto parts store installed for each of the car batteries(your thoughts).welcome any comments and suggestions, Thanks in advance!
Gordon
1967 MGB GT
1967 Porsche 912
1968 JAG E Type Coupe
1969 Porsche 911E
2013 Honda Accord

[dicklague]

I use batteries designed for the Mazda Miata. They are a little smaller than the Interstate 911 battery. You can get them in AGM versions for around $100. I have had very good service with these.

that voltage sounds low. I would check the cables and see if you have any problems there. Also test the CCA on your batteries with something like this.

Digital Automotive Battery Analyzer

I have one it is a great tool to let you know if your battery is up to snuff.

[RSTarga]

Not wanting to pony up for the Sonnensheins, I bought a pair of Miata Bosch batteries that won't leak acid on my front pan.

[javadog]

I'd be careful with any replacements that aren't identical to the originals in size. I've seen what happens when one of them shorts out to the car body and it is not pretty. I'd be damn sure I had covers over the positive terminals that can't come off.

I don't know how long your batteries have had a low charge, or if they can be saved. You might remove them, clean them, check the electrolyte levels and charge them on a bench, so see if you can save them.

Testing for proper alternator output, or for a parasitic draw is easy, so worth doing.

If you install disconnects, you'll need two and I would install them on the ground sides. You could also just unscrew the wing nuts that attached the ground cables to the car, I suppose.

You could also wire in a battery charger. I use Deltran Battery Tender Juniors. You have to keep an eye on them and also on the battery electrolyte levels. I don't leave them plugged in permanently. I'll plug them in every week or two to get the charge levels back up.

I have no experience with the charger you asked about.

JR

[sepia2.4]

Interstate 911 Batteries. Keep it original.

[HarryD]

Originally Posted by javadog

{snip}
If you install disconnects, you'll need two and I would install them on the ground sides. You could also just unscrew the wing nuts that attached the ground cables to the car, I suppose.
{snip}JR

If you put the switch on the positive terminal on the left (driver) side of the battery, you disconnect the battery from the loads. The battery on the right side is grounded on the negative side and the positive terminal is directly connected only to the positive terminal of the other battery.

[dicklague]

Originally Posted by javadog

I'd be careful with any replacements that aren't identical to the originals in size. I've seen what happens when one of them shorts out to the car body and it is not pretty. I'd be damn sure I had covers over the positive terminals that can't come off.
JR

Good point. I bought some plastic sheets with good insulating properties and installed them on the "ceiling" if each battery box. This insures that the terminals do not come in contact with the metal. The Miata battery is not quite as deep as the stock battery so i have a plastic spacer behind each battery to keep the terminals in the original position.

[javadog]

Originally Posted by HarryD

If you put the switch on the positive terminal on the left (driver) side of the battery, you disconnect the battery from the loads. The battery on the right side is grounded on the negative side and the positive terminal is directly connected only to the positive terminal of the other battery.

Not that he has a lot of room to attach a shut-off to the positive terminal, but...

It's always safer to install these switches on the ground side.

The two terminals on a battery are different sizes and the switches that are designed to install directly on a top mount terminal are sized for the (smaller) ground terminals.

FWIW,
JR

[Quickstep192]

I wanted AGM batteries because I was killing regular batteries. Also don't mind not having any acid. I used Odyssey 975's and built boxes to make them be the same size as the originals. I got terminal covers from the marine store, even though the terminals are fairly distant from the top of the battery box. I keep them on a ctek charger.

Here's a link that I posted a while back.

My Odyssey battery Odyssey

[Tremelune]

Lead acid batteries don't make much sense in 2015, and originality makes as much sense for batteries as it does for tires.

If you don't want to mess with fitment, get the same size/shape. If you think you'll lose sleep over it, get the same CCA rating as the stock battery. There is, however, room to optimize:

Aftermarket Car Batteries For Your Honda - Battery Science - Honda Tuning Magazine

Some take-aways from this random Internet article:

- CCA only matters if you expect to start your car at 0°F. If you never start your car when it's below freezing, you can go by the much more forgiving MCA in a battery half the size.

- If you don't listen to the radio with the car off regularly, and there are no other electronic gizmos that drain it, reserve capacity doesn't mean much either.

- Battery life has very little to do with sizes and brands and very much to do with how you treat the battery. If you put a charger on it every time you park it, your battery will last a long time. I just pulled a battery out of my '84 911 from 2006 (though I've never had a battery go this long).

For my next battery purchase in that no-gizmos fair-weather car, I plan to get an AGM battery with less than half the rated cranking power as stock. I'll let you know if it turns out to be a horrible mistake.

I had no idea '69s had two batteries, that's neat!

[69porsche]

Gents,
All good stuff that you have contributed to my knowledge-Thanks and safe motoring!
Gordon

[HarryD]

I have a single Optima (laying on it's side) in my '73. I have had it for years with no drama.

[Fixer]

Lithium Iron batteries are great. Light as a feather and do not lose charge when not in use. https://www.pegasusautoracing.com/productdetails.asp?RecId=12677&utm_source=google&utm_medium=cpc&utm_campaign=1178-406&gclid=Cj0KEQiA2b20BRDj4buduIG-y9EBEiQAhgMGFZCXeXhUMd3yYxVEB2MTaL9Xthx2Ygkoao314s Z57y4aAqT18P8HAQ