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Hello World,

I am needing a new battery for my 2.2 four cylinder 914. I have read many of the battery threads from recent years. I know many of you have had success with Optima, but I've also read about the quality concerns in recent years. The Odyssey seems like a good choice as I've not read any threads addressing quality concerns with this brand.
The Odyssey Group 42 standard size battery for our 914s is 600 CCA, is as heavy as a lead acid battery at about 40 lbs., but it is a plug and play(no extra bracket required). I am not opposed to this option, but like the idea of a much lighter battery.
Odyssey sells a PC925(330 CCA at 24 lbs.) and a PC680(170 CCA at 15 lbs).
My mechanic friend recommended that I stay within 100 CCA of the standard size Group 42 battery, which would mean at least 500 CCA.
My car is stored at a remote storage facility that does not have power, so a battery charger/tender is not an option for me. I currently disconnect the negative battery cable when not using the car, but will purchase a disconnect switch when I purchase the new battery. The car is not a daily driver, and it's not unusual for the car to sit for a week or two at a time without starting or driving it. I have a/c and a CLA for my cell phone, but no radio or other electronic gadgets and I don't run any of the above with the key on.
I've read where several of you have the PC680 or PC925 and have not had any starting issues, but I don't know how often you start your cars or if you use a battery charger/tender to keep it from draining down. I live in California, so CCAs are not as critical as other areas in the country.
Any thoughts on CCA ratings or other issues I should consider? For terminals, do you use the SAE battery posts or the M6 receptacles? Other AGM brands recommended?

I have the Odyssey PC925 with SAE posts and love it, but depending on the voltage your alternator puts out, I wouldn't recommend one if you aren't able to keep it on a battery tender (and one that meets the requirements by Odyssey). The PC925 also requires coming up with a way to keep the battery in place as it's smaller than a standard battery.
I've had Optima's for the last 20 years, never an issue. In the 914-6 GT Tribute for the last three. Best, MarkClick to view attachment
I'm running a PC1200 for 3 years on my 2.7 six with high torque starter. Works like a charm!
Just bought an AntiGravity ATX20-RS

Only time will tell.
Group 96R is a drop in, new Die Hard AGM is 31 lbs.
Running the PC680 on my 6 conversion. Over winter it probably did at least a 2 or 3 week stint in between runs. No issues at all. I'm running a hi-torque small starter.

Click to view attachment
PC680 for me as well on a 2.4l six with a high torque starter. It has sat for months over winter and started fine afterward, but that isn't an ideal situation for the battery. It would be much happier if you used quick disconnects and took it home with you to put on a charger. (its a good theft deterrent too if there isn't a battery in the car)
QUOTE(oakdalecurtis @ Dec 16 2021, 09:47 AM) *

i use an Optima Red, got about 8 years out of my last one, maybe because of this modification. Since I drive my teener in fair weather only and often on short trips, I put a tender on it whenever it's in the garage. I got tired of opening the engine cover and attaching it all the time, so I did the following modification. Now I pull in the garage and "plug in" the car...

Click to view attachment

Click to view attachment

I have the PC680 since 2 years now. It's very light and the car starts every time from the first time. But I always disconnect the battery if i don't drive the car for more than a week and from time to time I use a battery tender since the weather here in Belgium is too bad to drive a lot during wintertime.
To disconnect the battery I have the little green wheel at the negative of the battery. Very easy to install and very cheap. I also had to buy a bracket to hold the battery in place. Until now , I'm very happy with it. I have no radio and no AC, probably you will need a bigger battery or a really good alternator if you have them and use them a lot.
I only did this to reduce weight and I think the AGM's keep their charge longer ( when disconnected).
Click to view attachment
Slotty from this angle it looks like that positive terminal is so close to the metal tray. I'd feel worrisome, but it's probably further away in actuality.
I have an odyssey pc925 that is in one of my 911s. It had sat for 4 months and was down to about 30% charge so I took it out to charge it. Put it on a ctek trickle charger and came to the garage a couple days later to the worst smell. It had exploded. Talked the the vendor I bought it from and they said it had sulphated and was over 2 years old and I was out of luck. Called odyssey and they are sending me a new battery. It was less than 2 1/2 years old. I am now leery of trickle charging while in the car. No one has any idea what happened. I use the charger rotating to all my batteries and never had any issue. Very nice of odyssey to replace although I haven't seen the replacemnent yet.
QUOTE(nditiz1 @ Mar 18 2023, 06:11 PM) *

Slotty from this angle it looks like that positive terminal is so close to the metal tray. I'd feel worrisome, but it's probably further away in actuality.

Looking at the pic, I was thinking exactly the same thing, but in reality it's not that close. Maybe I'll put some insulation in between, just to be sure.
I've used the Optima batteries in quite a few projects.
For vibration resistance, no gassing, and no acid leaks they are hands down the best.

My problem is they haven't lasted over 3 years for me, and their warranty is for 1 only.

They also have to be either charged in parallel with a lead acid battery or charged with a special AGM smart charger.

I will use an AGM battery in my 914s but it will probably be a normal mass-produced battery like the MTX/MTZ line from Interstate.
It helps that I am an Interstate dealer and can get these as cheaply as anyone else.

The MTZ line has the longest warranty from Interstate (48 months free replacement) and I'd expect one to live 6-8 years.

Interstate batteries is an Optima wholesaler, and I can get those at bottom price as well.

I'll still go normal over Optima for a street-based vehicle.
I have Optima batteries in every single vehicle I own. They are all the same size too. Never had an issue with them at all. But if I do, I can pull the battery from a 914 and put it in the daily drivers and keep going. And I can walk into a FLAPS and buy a new one there.

The factory size battery for our E34 BMW was over $300.00 for a lead acid standard battery, and had a 3 week back order. The optima was less, had a higher CCA, and was available immediately.

QUOTE(yeahmag @ Mar 17 2023, 06:02 PM) *

Just bought an AntiGravity ATX20-RS

Only time will tell.

I really like the idea of a 4 lb battery.
I’m also using a high torque starter so that saves another 5lbs.
I’m going to try the cheap version first.
Great discussion of batteries, thanks for the info. I have a question though:
I have am Optima 34R red top.Its a least 10 years old. I wonder ifI should replace it even though it still starts the car. The car is driven 100 miles a weaken average and I attach a battery tender when it sits.
My only complaint with the Optima is its weight......
If you are interested in a lighter weight Optima battery, this is on their website:

800Amp Lithium Battery.

Brand new, so no one has any experience with it yet.

The red top 34R is 38 LBS. The Orange top is 7LBS.

I don't know if it will work, but it is something to think about.

The Li-ion batteries scare me enough to not run them in anything but a track car.

My youngest, Michael, was a track marshal for MSR (Motor Sport Ranch).

If any of you have video where a young blond "punk" made funny faces in your camera just before you left the pit area, that's my son...

One of his duties was fire suppression.
A Li-ion battery fire is very similar to a magnesium fire. Nothing but burying them puts them out. 20 minutes AFTER you think you have it out it starts back up.

A lithium-ion battery fire almost always takes the entire car with it.

These are NOT cheap batteries either. A 200K track car usually gets the very best equipment.

Owners are pissed when this happens...

They have lost multiple cars and garages to Li-ion battery fires at MSR.

I do see the benefits to the Li-ion batteries but until these becomes less flammable, I'll stay with heavier batteries.

I wish my Optimas lived as long as Clay's and Jim's...
10 years is a shitload for any battery.
Had mine lived longer I'd recommend them over everything else.
Optimas can fail but when they do they just barf their guts out of the cases.
I have not heard of any fires being associated with this.

The usual reason for Optima failure is long term trickle charging with equipment that is not specific for Optima batteries.

The Optima smart chargers are a bit on the expensive side and don't work seamlessly with lead acid batteries.

Out at MSR, Porsches gained the title "fire lizards" due to the fact when they leave the track and slither into the grass they catch it on fire far more often than any other brand of car...

PCA and Porsche events at MSR were always super professional with extremely friendly people. Michael loved to work when the fire lizards were running.

The motorcycle crowds were exactly the opposite...
I've used the PC680 for years now with good results. My car has a minimal electrical system and I disconnect the battery when not in use. Mine is on its side but flipped the other way around vs the photo above to give more clearance from the battery tray lip - it's still a bit close for my comfort but I have an insulated cover over the + terminal as required by racing rules.
Have had Optima red tops in my 914 since ~1992.

I think I have only had 2, maybe 3…so easily 10 years per. The big attraction back in the 1990s was avoiding hell hole rust. But they are heavy, so I think about an Odyssey or Anti-Gravity. Or that new orange top from Optima. For both of my fun cars, as I value less weight over more hp.

Having just lost a fair bit to a house fire (electrical, but not car related), @technicalninja has me rethinking the value of 30-40lbs saved vs having the car/garage/house.
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