shammerman

@UH2 - Batteries+ would have done it for you while there…. They did my Z8 a few years ago.

UH2

Yup I saw that on the door as I walked in but..I was driving my Macan and not the 911 and honestly I have trust issues lol.

UH2

You're right it doesn't, but like I said there were other signs and data points that led me to the conclusion I did. The fact that it cranked slow after not being driven and then was somewhat better after driving it for a while, plus the PCM wigging out plus a 10 year old battery ...well..all signs point to the battery.

IXLR8

In your case, yes but in the case of the 997, it would start when the engine was at ambient temperature (first drive of the day), but would hardly turn over once the engine was warm on re-starts. A lesson RLers might keep in mind should they come across that scenario. Of course our 991s are newer, but as they age...

UH2

That's a bit different than my "slow cranking". Like, if you had heard my car turn over and had never heard another 911 with a newer battery turn over, you wouldn't think anything was wrong. It had been like this for years but it started without fail every single time. It wasn't until I put the new battery in that I was like "Oh...it actually cranks faster than I thought was normal".

What you're describing sounds like you were crossing your fingers that the car would actually start when it cranked slow? If that's the case then yeah, that's not what I experienced. And actually in my case the restarts improved the cranking speed...just not to the same level I'm experiencing now...which is normal for fully functioning battery.

MingusDew

These cars are so finicky about voltage levels, it doesn’t seem to take much from the battery being all “it’s 5+ years old, the original, doing great!” To yet another “weird error message and dash lights are on, what’s wrong?”-post. One day fine, next day stranded without warning. YMMV of course, but why risk it?

Levy

agree 100%. after reading all the crazy crap a not so good battery can cause, i'll be replacing mine every 4-5 years regardless of how it functions. DIY so cost won't bother me much compared to the nightmares i read others going through when the battery gets iffy.

barncobob

ive found 5 years is the sweet spot for replacement

bkrantz

After 5.5 years the original battery in my 2017 started showing signs (a few unprovoked error messages, like for bad L and R tail lights, and auto stop/start not kicking in). I replaced it with a Antigravity H6 Group 48. It has worked perfectly so far.

garthg

Don't replacement batteries now have to be registered with the car's ECM?
I know BMW/MINI have a computer-controlled alternator that requires such. And I think I saw somewhere the same for Porsche.

IXLR8

I changed my mind after seeing the sensors on the negative post on my vehicles. My 2015 991.1 has it and so does my 2017 Acura RDX have that sensor. Maybe my previous 2013 VW Jetta TDI had one but if it did, the sensor must have been elsewhere.

I might be wrong, but I can see it only needing the Ah rating of the battery and the battery type (FLA, EFB, AGM, GEL, etc). The serial number and manufacturer of the battery is probably unimportant. I doubt very much the ECU will have a list of endless battery manufacurers and serial numbers.

JimEb

My 2014 had the OEM battery until i replaced it last spring.

It was working fine but when I checked it with a load tester it said “REPLACE”.

IXLR8

Was it a carbon-pile load tester or one of those small conductance testers?

GSIRM3

I just replaced my OEM battery on my 2015 GTS. It still started fine and tested OK, but I was getting concerned it might strand me somewhere, but it was 8 years old and still strong. These AGM batteries last longer.

na4life

Just replaced my battery on my '15 GTS as well. It completely died (wouldn't even jumpstart and the trickle charger refused to charge it). Swapped to a lithium anti-gravity battery and it's MUCH better. Not only is the lithium battery way lighter it also has jump starting built in. Was really simple to do at home. Just need some metric socket wrenches (ideally with an extender) and some ratcheting wrenches and a torx screwdriver. These batteries used to have some gotchas but they're all ironed out now. Plug and play.

The main thing is after replacing the battery if it was completely dead you'll have to deal with some warning lights and oddities for the first few drives. For example, I got a warning about the steering range. Just had to move the steering wheel back and forth to both extremes and restart then repeat and it went away. Also had to reset windows and PDK initially went into limp mode so had to warm the car up then do a PDK relearn. I think I only had to do all this b/c the old battery was completely fried. If your battery isn't dead yet I recommend keeping the car on a tender to avoid having to deal with this stuff (not a big deal but easier for sure).

You do not need to specially code the car to have a new battery. I believe it does reduce the charging speed if you don't code it but not a big deal. Also, if using a lithium battery remember to only use a lithium trickle charger.