yoda888

Yes, yet another battery question related to the 991. I did searching on rennlist, google, and chatgpt as well.

My 2014 battery is getting weaker. The stop/start function doesn't work, and the battery was recently tested and the capacity is below what the minimum should be per the mechanic. Not bad as it looks like the original battery is in the car so I can't complain - basically 9.5 year old battery.

I don't drive the car daily, nor is it freezing here. I know you can go with h6, h7, and h8 sized batteries. My preference is an H7 or h6. I think H8 is overkill. When I look online all the various battery vendors out there always says H8. If I manually put in the H7 size, I get "does not fit your car." I'm looking at Interstate and ACDelco as these are tried and true and in theory should last 7+ years easily with my situation.

H7 and H6 should fit without an issue. What is the min specs I need from CCA, etc? For those of you who have installed an Interstate or ACDelco, what size did you go with and what's the p/n? I found this battery: MTX-48 H6 which doesn't fit my 991 per Interstate. But it does fit 2017 991. Does the .1 have that much more electronics vs. a .2?

I haven't looked into programming for a new battery yet, but I'm hoping that will be straightforward!

MingusDew

I don’t have the specs handy, but I remember picking the MTX-94R (H7) because it met or exceeded every spec of the OEM battery (CCA, etc.). I also picked that tier battery for the warranty length, so there are other -94R batteries that might be comparable but lower cost. The H6/7/8 batteries are all the same width, just different length. The bracket is bolted down and can be repositioned by removing a bolt, very easy. You’ll see when you take out the old battery. From what I recall most H6 batteries have some reduced capacity, but probably still would work fine. The H8 seems like overkill to me, and it’s significantly heavier.

bkrantz

Very happy with my Antigravity H6.

IXLR8

FYI, the battery date code is stamped into the top of the negative battery post. It should be a Banner battery. Mine is in its 10th year with no issues.

Replace it with the same sized AGM battery.

Antigravity

To make this easy, you don't have to worry about any ratings or specs except that it is and H6 or H7 size model and you'll be good, they all have roughly the same specs no matter what the marketing says. H7 offers a little more capacity.. Just stay with a reputable brand, and the Walmart Platinum Series is a great battery and is the same on with a different lable as some of the other top brands. At 9 years you should probably do the programming for it, but you will be asked for a code # from the battery which you can use any one from a Porsche or VW battery, but you'll have to find a picture from one of those brands of batteries to get the code when you register the battery... so that might be a little of a hassle.

SilverSFR

Good thread on updating new battery with pictures of Banner Porsche battery codes

Updating BMS - Rennlist

Joec500

Scott, you guys planning any summer sales for your H6 battery for our car? I assume the 40AH is the miniumum we should go with for a typical Daily Driver with no charger being driven at least once a week?

Tier1Terrier

My 8 year old original OEM battery just died yesterday. I think you will have a hard time finding a battery closer in spec to the OEM Banner than the Interstate 80 ah 94R 850 CCA. Picked one up at a nearby Costco yesterday for $169 with free 3 year replacement. I expect it to last significantly longer than that, but for that price and 20 minutes of work, that sure beats spending $600+ at the dealer. I literally just posted this video detailing the installation procedure and what information you'll need to update the BMS using an ICarSoft POR V2.0. I assume the process and required information will be similar for other OBD tools.

Porsche_nuts

Good vid, but you should unhook the negative terminal first and then positive. To install, positive terminal first and then negative.

IXLR8

Maybe the owner wanted to be a "welder". Like so many on the planet earth, even some so-called experts, too many with very low technical skills or aptitude that are wrenching or in the trades. Ask me how I know having had to repair jobs in a new house that I bought done by "licenced" tradesmen. Amazing how an un-licenced person can do a far better job...damn those water pipes have not leaked in 27 years since I soldered them.

IXLR8

For those registering a H7 battery with the same specs as shown below, here are the numbers on my 2015 Banner battery:

Banner AT Made in Austria
12V 80 Ah 800A EN
*205 BA24F4PR0CQ*
Porsche Part Number: 999 611 080 12.

And instead of relying on some tech feeding you bad info due to a lack of knowledge, maybe invest in a battery tester. They go for well under $100. Sure, not as good or possibly as accurate as some of the high priced test equipment we used in the battery lab I worked in before retiring, but it is better than nothing and can be used to monitor a trend in battery health. Note, battery testing should be done under the same "fully charged conditions" to be accurate.

Test performed recently on my 9+ year old Banner battery...

Antigravity

Unfortunately it won't be until Labor day, which is a 15% discount, but we do have a standing 12% discount for Rennlist members, so you would email us to get the code. scott@ or chad@antigravitybatteries.com

DR911s

Excerpt from earlier post by Antigravity Battery sponsor: Just stay with a reputable brand, and the Walmart Platinum Series is a great battery and is the same on with a different lable as some of the other top brands.

Last fall [2023] as preventative maintenance after the even older battery in another of my cars failed totally without any warning, I replaced the OEM BANNER brand battery in my 2017 C2S with an H7 size AGM battery from Walmart which came with a 4-year replacement guarantee. The replacement battery was in stock at one of the local Walmart stores in my area, and was less than 2 months old from its date of manufacture in Germany. Cost including sales tax was about $200. Fitment was perfect. I reset the Battery Maintenance [charging] system using a scan tool. No issues thus far.

DOUGLAP1

Lots of good advice here. I would add that in my experience, the batteries at a retail store are almost always in a state of low charge. I suggest charging over night to at least 12.8 Volts, or whatever the battery mfr. recommends for a fully charged battery before putting into service.

IXLR8

Exactly why when buying a battery I look at the date code and bring a pocket sized Digital Multimeter (DMM) with me to measure the voltage prior to buying.

This past May, some of the AGM batteries at Walmart had a date code of 3/24 (March). AGM batteries have an extremely low self-discharge when sitting on the shelf, much lower than a conventional FLA battery.

When buying a battery, I look at life span vs cost and when I get 9+ years out of them (so far), $200 vs $1200 makes battery choice much easier.