FirstF80InSpace

My 992 is currently stored for the winter in my garage. I don't leave it on a trickle charger. I just top up the battery every couple of weeks. (I know, I should just leave it plugged in). I have the Li-Ion battery.

I didn't charge for a month and came out to a completely dead 992. I popped the hood via the fuse panel method. Connected the trickle charger and it wouldn't charge.

I then managed to start the car with a spare car battery. The car started fine and there were all these error messages on the dash. I let it run for around 10 minutes and then all the messages went away.

I turned off the car and connected the trickle charger back to the battery. The trickle charger showed the battery was fully charged.

My question is it possible for the battery to be completely charged with the car running for just 10 minutes? I find that hard to believe.

kim9701

Fully charged from 0 to 100% in 10 minutes? I say "no way".

F8Driver

The lithium battery will shut down around 10.6V IIRC, it's not zeroed out. Dead car will require the requisite procedure to unlock door, jump fuse box, open trunk and charge. CTEK Li charger has a special mode that will overcome the battery's reluctance to accept a charge with the dead battery scenario. A suggestion. install the charging cables so that they're accessible from outside the car (there are several methods posted here), no hassle hooking up the charger.

I suspect the 10 minutes run time just got the battery to a charge level where it could restart the car, not 100%.

andreas722

Two recommendations:
1. Just letting the car run at standstill for 10 minutes after the battery is dead will not be enough. You need to drive the car for 20-30 minutes allowing it to get up to high speeds 60+ mph. This will recharge the battery.
2. Take your car to the dealer - Porsche released a fix in November 2022 that addresses battery drain issues. Essentially the PCM was draining the battery, and they need to do an update.

CodyBigdog

Excellent post 👍

GoCards67

Does the fix you mentioned affect all batteries in cars with PDK or only Lithium? I don't have RWS but have constant issue with radio forgetting settings I think because of excessive drain. Wonder if that is related?

andreas722

My car is a 2020 992 4S without RAS and does not have Lithium Ion battery, and the "WNN3 Re-programming of the connect control unit" fixed my constant battery drain issue.

FirstF80InSpace

Question for you. I'm still having the same issue. And my car is scheduled to have the WNN3 recall done in a couple of weeks. When I hook the charger up, the battery is showing full charge. So the battery is not drained. Yet I keep get a battery low warning on the PCM and my battery is putting itself to sleep.

Were you having an issue where your battery was actually draining, or were you just getting a low battery message even though your battery was full?