Jjcrawdad

Driving my '05 C4S and got a red warning message on the center screen something to the effect that the battery failed. Got it home and it now sits on trickle. The battery is dated 2018. Figure I should find a replacement. If I pull and replace it, are there any special resets or anything that I'll need to do?
Has the stock base sound system.

brontosaurus

Nothing to do.

While you are in there you could go with a slightly smaller battery (H5/Group 47) to save ~10lbs. Fits with no modification & was the OEM GT3 battery size.

allcool

Hmmm, never realized the h5 was the oem gt battery. Thanks, that will be my next battery. Now I've got agm h6 batteries, seems about a 4lb difference with the h5. great, I'll take all weight reductions I can find....

jmo

TheChunkNorris

Damn man I had no idea. My fat *** had to step into the frunk because the battery it came with was massive.

996-CAB

Did you notice the voltage level on the voltmeter in the days leading up to the battery failure? If it was hovering around 12 and sometimes below, your real issue is likely the Y cable or the starter/alternator cable. If you don't recall the voltage falling leading up to the failure. when you put in the new battery, keep your eye on the voltmeter. Hovering around 12 when the engine is warm is a sure sign the cable is going. For comparison, when you have a new alternator, Y cable and battery, the voltmeter starts out at 14 and hovers above 13 when the engine is warm and all the fans are on. It never goes below 13.

Jjcrawdad

Thanks for the tip! I was watching the voltmeter and didn't see it get down to 12. Was 13 warm. Hope it's the battery and not alternator or y cable. The new battery was expensive enough! And yes, looks like I'll be standing in the frunk to do the swap!

Mike Murphy

I’m not aware of any 996 warning light for the battery. Does one exist? I thought the light was for the alternator.

Jjcrawdad

Really hope not! After I complete the battery change I'll update this thread whether it's resolved.

GC996

yeah, i've had a couple of dead batteries over the years on my 996 and never saw a warning light. Don't know about the alternator because I haven't had one fail just yet.

Gary12000

You will likley have to reset your windows check your manual for a how to... its pretty simple i think... i think the radio code was only the earlier stereos...

Mike Murphy

Agree with this. I also went with the smaller battery.

Other than starting the car, a larger battery is really only useful for instances where you’re pulling a lot more power than the alternator can supply, or you like to run power, accessories, and lights with the engine off, which I never do. I used to do that kind of stuff all the time (car audio), and I went through a lot of batteries back then. Now I let the alternator run everything, and the batteries last way longer.

Jjcrawdad

Well, crap! I must not have noticed after the warning message. It was reading 13 warm just prior to the message; i watch my guages closely; so was a quick failure. Just started her and the voltmeter is sitting at 12 and not moving with a rev. Returning the new battery and talked to my indy shop. Going to flatbed it to him next week. He said with a fully charged battery and all electric items turned off, I could probably drive it the 45 mins to his place, but don't want to risk getting stuck on the highway.
Thanks for the tips!

isalos

have a look at this post:

https://rennlist.com/forums/996-turb...l#post19502331

if voltage drops after swapping the voltage regulator, go for the y-cable as suggested here:

https://rennlist.com/forums/996-foru...l#post19517734

FunWithPaul

If you have the E-throttle (DME ME 7.2 or later), after a battery disconnect, you need to turn the ignition on for 60 seconds, then off for 10 sec to reset the throttle position.
And do the window reset procedure, so your glass drops the few mm when you pull on the door handle.

From Bentley manual 27-2