991.2 Battery Replacement Update 2024
 

I know there's a lot of posts on this one but thought I'd share my experience. My 2017 991.2 original Porsche battery (8 years old) died over winter even though I had it on charger.I checked various sources and landed on a Die Hard Platinum AGM, Group 94R H7 (Advanced Auto - Auto zone had the same exact thing rebranded). It's a direct fit replacement. $272 after taxes and core. I called the local Porsche dealer and a new Porsche battery was $472 after taxes and core. The hardest part was getting the lower 13m nut off the battery bracket as it's a tight space. The second hardest part was lifting the 52lb battery out. I laid a bunch of heavy duty blankets around the area as to avoid any scratching. Overall took about 20 minutes to remove. No ECU upgrade required. Everything fired right up as like nothing ever happened.

Best!

Thanks for that information. Other Rennlisters who got an aftermarket replacement battery seem to be installing group size H8s. You are the first to mention an H7.

I'm about to replace the original H6 70A Banner AGM battery in my '16 GTS. Porsche dealers in my State want $375 to $475 plus core and sales tax for the same battery, and the only batteries they have in stock are more than a year old. They say it takes 5 to 7 business days to order a battery (from Atlanta) and there is no telling how fresh it will be.

I had an Optima Yellow-top battery that performed very well in my '98 Corvette for many years, and I have an Optima Red-top in my RX-7 that is going strong after 7 years, so I checked to see if there is an Optima available for my GTS. They offer an H6, 72A 800CCA Yellow-top battery that should be fine, but their website says it won't fit, and that they do not offer a battery that fits my car.

As for other aftermarket AGM batteries, when I searched by vehicle and entered the make, model and year of my car, all the websites for auto parts and battery stores listed only size H8 batteries. When I searched by battery type, only one site said their H7 would fit (Advance Auto - DieHard).

Prices for AGM H6, H7 and H8 batteries are all about the same, so I don't understand why they all push H8s as the only replacement that will fit my GTS when an H7 or even and H6 like the Optima should do the job as well or better than the original Banner H6.

Batteries Plus has great prices and check out there website as they often have a 20% off coupon. You need to match the Group number 48 number (LxWxH and dimensions). H6-H8 will all work. bigger the number the bigger battery length and the battery Amp Hrs but still 12V. The battery bracket you speak of just moves in our out to fit the different sizes of battery. I also chose the Die Hard Platinum AGM Group 48 STI48AGM. Its look and size are identical to the banner.

Batteries Plus Duracell STI48AGM and 10% off if instore pickup.

If you guys are ever interested in Lithium we have the H6 size and it weighs about 15 lbs, and has wireless built-in Jump Starting so you will never be stranded by a dead battery or locked out of the frunk. Yes they are more expensive, but for those who can use the features it a definate advancement over lead/acid saves 35lbs and also has up to 3x the lifespan. We also have 15% off sales 4 times a year and put them on rennlist when we do.

Youc can see the video and product at this link. https://antigravitybatteries.com/pro...tive/ag-h6-rs/

I have two AG batteries and can confirm that they are great and the company behind them is great. I have one car that lives in offsite storag; I park it, take the battery out, bring it home and put it on the charger. Takes 5 mins and is super light. I'd never try that with the 50 lb version... :)

What amp-hour did you go with?

I'm not sure how much it matters, but both the Die Hard and Duracell AGM H6/group 48 batteries, like the original Banner H6, are rated at 70 AH, but neither has the same CCA rating as my original Banner.

The Banner is labeled as 760 EN, which converts to 800 CCA, while the Die Hard and Duracell are only 760 CCA. You'd have to go to an H7 in those 2 brands to equal or exceed the Banner's CCA rating, or consider the H6 Optima yellow-top, which has 72 AH and 800 CCA but costs about $100 more than the Die Hard or Duracell.

This is not a battery thread until @IXLR8 comments :D.

Serious question though... I know you said no ECU updates were required. Did you determine that based solely on everything working as it should after the installation?

All I can say is I am now going into the 10th year with the factory installed Banner H7 AGM battery in my car. Still short of the 14 & 16 years I got out of a plain old conventional FLA battery.

Many on Rennlist have said that. And as I have never needed to replace my battery yet in the 991, I might as well use my iCarsoft CR MAX and do a battery registration when the time comes. Will it make a difference? Who knows.

I have read (on forums) that connecting to the battery terminals directly when using the charger/maintainer by-passes the "sensor" and defeats the purpose of it all. Well that is what I do and my battery seems to last, so that method of how I connect seems to have little effect if any. Show me a white paper on the subject as I believe in facts and not fiction, the latter often found on the internet.

hear hear. I am another person in the "AGMs last me basically forever, what on earth are you people doing to your cars" camp.

We're living up north where it is cooler. Better for batteries.

Wanna see a football field full of dead AGM batteries in Iraq? ;)

My wife's 2017 AMG has a smart alternator with BMS, as do the 991.2s (from what I can see, the 991.1 does not). When her original battery failed I installed a new one without registering it. That battery failed in a bit over six months. Rinse and repeat. Same results. So, looking into these failures, the adaptive battery charging algorithm needed to be reset to avoid cooking the new batteries. I bought a reader that could do this by registering the battery. All appears to be fine now. But a failure to register may result in future failures.

Search on this in the 991 Forum. People who are smarter than me agree.

Interesting. Is there a way to register a new battery via ThinkDiag?

Somehow I doubt that. What kind of voltages are you seeing and at what temperature where you think you are "cooking" the battery?

I do not know what the steps are to register BMS, but the AMZ blurb says it can do it.