I have a 992.2 Carrera that was delivered to me November 2024. It has 6000 miles on it. It seems like every 2-3 days it has a dead AGM battery. I do not have any aftermarket parts plugged into any USB ports. It is all stock so no parasitic drain from anything like that. The Volt meter on the dash says the alternator is charging at 14.2-14.5.
I seems like every time my wife and I are dressed up for a night out I have to jump start it. Now I have to keep it on a tender on a daily basis.
I know I should take it to my authorized dealer but it is a 4 hour drive to the nearest one so I have to take off work to get any work done on my car.
I took it to an auto parts store and THEY say the battery is fine but I am not sure about that.
Has anyone else had this problem before I start getting hotel reservations?

 

There have been problems with lithium batteries but I have not heard about anything widespread with AGM. If battery is "fine" it must either not be charging properly or something is draining it while parked. Has this has been happening for 1.5 years?

 

2 weeks after I got my car another car at a red light bumped the back of my car with their winch on the back of their jeep. It took 8 months of sitting at the Porsche authorized body shop to replace the bumper/back end. I fear that may have drained and damaged the battery from all of Porsche's PCM cycling. The voltmeter on my dash is always in the 14v range.
Do you think this may be the problem? I tested it at Oreilly and they said it was fine but I fear their non Porsche specific testers may not be reliable

 

992's are notorious for battery issues. Every single one of our development cars has had to have the battery replaced. In fact, our 992 Turbo is on battery #4. We also had our 992.2 GTS 12V lithium battery go dead after only 300 miles on the odometer. This is a known 992 problem unfortunately.

-Charles@M

 

Something is obviously wrong. I think your only course of action is to take it to the dealer. Give them the background, battery always needs a jump, and see what they can find out.

Bottom line, your car should not need a battery tender for a few days non-usage.

 

AGM batteries lose a lot of life after they have been severely discharged. If you're still on the same battery after it's been discharged several times, it's likely now damaged. This would explain why it's dying every few days off a tender.

Replace the battery with a new one and keep the replacement on a tender if the car is not going to be used for more than a day or two.

 

You will probably need to buy a new battery and a battery maintainer. Put it on a maintainer if the car will sit for more than a few days and / or after repeated short trips.

Porsche's solution to this is language in the owners manual....

 

If your AGM battery has been fully discharged at some point, I agree with others here that it likely has been damaged and won't hold a charge for that reason.

Just as a point of discussion, you say that your car is stock and has no parasitic drains. Do you have Stargard? Many dealers mandate installing this anti-theft tracking device to new cars and since it is hooked directly to the battery it does create a small load that is always present. Also, do you keep your key someplace near the car? If so, it may try to continuously communicate with the car which can also cause a small drain. Either of things could stress an already weak battery.

 

Both of my 992s have had zero battery issues. Both are S models, 2020 and 2024. Neither have lithium batteries. I do use a battery maintainer for winter storage and when I will not be driving for more than two weeks. But a few days should not cause a problem. I suggest getting a new battery and keeping it on a maintainer for a few weeks to see if the problem recurrs.

 

You either have a parasitic draw of some sort or the battery has an internal bent wire short or a defective weld between two cells.
Test for a parasitic draw (see below). If it's less than 30 mA (0.030 Amperes) replace the battery. You can use an inexpensive test light instead of an Ammeter. FWIW, It takes roughly 100 mA to make the filament glow just barely enough that you can see it. If you're OCD about such things replace the word "Test Light" with "Ammeter" and you'll rest easy.
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1. Obtain physical access to the Battery. Ex: Hood/Frunk Open, any Access Covers or Beauty Panels removed.
2. Turn everything “Off”. This includes: Doors Closed, Lights “Off”, any and all Accessories “Off”, the Ignition must be “Off”, no foot on the Brake Pedal, Manually Trip the Frunk Latch (Frunk Light) if you have the hood open, etc. Basically, if it has a switch, it needs to be “Off” and untouched by human hands. It needs to remain this way for the duration of a “Parasitic Draw” test.
3. Now place any Key Fob(s) in a Faraday Cage or place all Key Fobs a very long, long way away from the car. Ex: If clicking the lock/unlock button on the Key Fob is recognized by the car, that’s to close.
4. Wait for ALL systems to time out and go to sleep. (~7 Minutes on my 2021 C2S)
5. Attach a redundant Ground Wire between the Battery Negative and a known good Ground Point. Verify your redundant Ground Point is in fact part of the car’s ground system before proceeding.
6. Remove the Battery Negative Cable from the Battery or from where it attaches to the vehicle. You must do this without disturbing the redundant Ground Wire. (Plan ahead.)
7. Connect an Automotive Test Light (12V/3W) between the Battery Negative and a known good Ground Point.
8. Remove the redundant Ground Wire
9. Test Light Bulb:
   • > Light On= Bad (Or not all timed systems had gone to sleep.)
   • > Light Off = Good
10. Re-attach redundant Ground Wire
11. Reconnect the Battery Negative.
12. Remove redundant Ground Wire.

 

Yep, you answered your own question. It died in the shop. A new battery should be covered by insurance.

 

I have never heard mention of any tracking device installed in my car. Do they put these in cars that are leased or financed? Mine is not leased nor financed so I doubt it.
By all you and others' help, I am starting to really believe it is because the full discharge theory. I am sure through the 8 months it sat at the Porsche authorized body shop waiting for the rear bumper cover to come in from Stuttgart they must have jumped it and moved it around and then let the battery drain completely several times.

 

FWIW, my car was purchased for cash but the dealer still installed the Stargard unit on arrival and then insisted that I pay for it. Another form of last-minute ADM which p*ssed me off but wasn't worth cancelling the transaction over. I know some other dealers do this as well and I'm not the only person this has happened to.

I removed the unit as soon as I got the car home. Glad you didn't have to deal with that. Good luck with your battery situation.

 

Most of the points above are covered well and quite correct. If the AGM battery was deeply discharged, it has likely been permanently damaged. It’s also common for dealers to install tracking devices—sometimes without clearly disclosing it—which can place a continuous drain on the battery.

Once a lead-acid or AGM battery experiences a deep discharge, it loses capacity and its ability to hold a charge effectively. In many cases, the simplest solution is to replace the battery. From what you said that the battery was deeply discharged at the Autobody shop that is probably a given...and might be the simplest solution.... then you can also check the other issues like parastic draw after doing this... but all this was stated by others above so I'm just confirming our experiance with what others are saying also.

If you’re considering lithium (which is more expensive), there are several meaningful benefits. For example our Antigravity Lithium batteries are protected against deep over-discharge, so situations like extended storage or body shop use won’t/can't damage the battery. It includes built-in protection circuits for over-discharge, overcharge, and other conditions, called a BMS (Battery Management System).

Additionally, they feature built-in wireless jump starting, so you’re never stranded with a dead battery again. While the lighter weight is a nice advantage, the biggest benefits are significantly longer lifespan than AGM due to 3x more actual cycles (cycles means full discharge and recharges of a battry) offered by Lithium Batteries, built in protections that prevent those accidental over-discharges which can damage AGM/Lead/Acid Batteries. They also offer stronger starting performance, and the convenience of integrated wireless jump starting, which as you have seen yourself can prevent you from just being able to easily start your car and drive away no matter what.

 

This happened to our RS6 with an AGM battery. Brand new car , sat and battery got discharged. Wouldn't hold charge after that.