992 Turbo Dead Battery Charging

Tech and talk about the 991 and 992
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Tom
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The 992 Turbo S comes from the factory with a lithium battery. On these batteries, special circuity detects when the charge is getting too low, and then completely 'deactivates' the battery. The battery still has power, but it's essentially disconnected from the rest of the car. When this happens, you won’t be able to pop the trunk to jump the battery, and you might be locked out of the car entirely. Ask me how I know! If you find yourself in that situation, here’s what you need to do!

1. Getting into the Car. To get in the car, there is an emergency (physical) key inside the key fob, which is used to open the driver door using the hidden key hole under the door handle.
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2. Emergency Trunk-Opening Terminal. Once inside, you then need to supply 12 volts to a special terminal inside the fuse box, which allows you to pop the trunk open using the button in the door sill. The special terminal is located in the driver footwell fuse box. It’s red with a drawing of an open trunk on it. You need to pull this red terminal all the way out, and put the red/positive jumper cable on it, and the black/negative jumper cable on the exposed metal catch in the door jamb (or any good chassis ground point). Once power is applied, it will allow you to pop the trunk using the button in the door sill.
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3. Getting to the Battery. To get to the battery, you need to pull off the black plastic cover at the front of the trunk. See pictures below. No tools needed, very simple.

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4. Charging the Battery. To ‘reactivate’ the battery, you need to use a battery charger or jumper cables from another car to charge the battery, using all standard safety precautions. Red/positive goes on the positive battery terminal, and the black/negative clamp goes to the special chassis ground post show in the pictures below. It should only take 10 minutes or so for the car to spring back to life. At that point, you can start the car and drive it to further re-charge the battery.
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5. Warning about Trickle Chargers. One word of caution: most trickle chargers don’t deliver power if they don’t detect a battery, meaning they don’t work well (if at all) for reactivating a lithium battery once it’s shut down. Read the manual for your charger, as most (CTek and Porsche) have special modes that claim to deliver constant 12v even if no battery is detected. I tried for a long time and could never get my Porsche charger to do that, and finally gave up and used a 30-year-old (non-smart) 50 amp battery charger. Another car and a pair of jumper cables would work just as well.


6. Check for Warning Lights. Depending on circumstances, you may or may not need to get dash warning lights cleared at the dealer. In my case, once the battery woke up, all was fine with no warning lights on the dash. Others have reported warning lights remaining on, which the dealer had to clear. Still others say they had warnings for a week or more, which eventually cleared themselves. Either way, driving to the dealer after reviving the battery beats towing it to the dealer. 😊


#1

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RAD911
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Thanks for this. It is very similar for the 996, 997, and 991. I had to do this for 996TT this weekend. The battery was extremely dead. I had put a new battery in this April and have not used it for maybe 2 months. I am thinking there must be something draining it while in my garage. But I do know that for the 996TT, that arming/locking the car will allow the car to use less battery power when sitting. But that does not seem to be necessary for the 991 and probably not for the 992.


Current: 19 9Y0 S, 17 991.2 Carrera, 04 996TT Cab, 80 911SC Targa, 21 Hellcat RE, 21 Ram 1500, 20 JT Rubicon
Past: 99 996 Cab, 06 997 Carrera S, 13 991.1 C4S, 11 970 TT, 05 955 TT, 08 957 S, 12 958.1 S, 12, 958.1 TT, 13 958.1 Diesel , 16 958.2 Hybrid

#2

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This happened to me a few weeks ago.
In my case, the "battery low" light did not go off after a week of driving.
I went to the dealer, and they tested the battery. The battery itself was holding a charge well and performing properly, but the aforementioned BMS (battery management system) that resides inside the Lithium battery was malfunctioning. This can't be fixed, so they replaced the battery under warranty.
Since then, I've bought a NoCo battery booster pack in case this every happens again. As well as the Porsche Pro charger.

M


#3

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Tom
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Mikster wrote: Mon Feb 14, 2022 12:35 pm This happened to me a few weeks ago.
In my case, the "battery low" light did not go off after a week of driving.
I went to the dealer, and they tested the battery. The battery itself was holding a charge well and performing properly, but the aforementioned BMS (battery management system) that resides inside the Lithium battery was malfunctioning. This can't be fixed, so they replaced the battery under warranty.
Since then, I've bought a NoCo battery booster pack in case this every happens again. As well as the Porsche Pro charger.

M
Out of morbid curiosity, did they tell you how much that battery would cost if you had to buy it yourself?


#4

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Nah they didn't.
I know you can buy the OEM battery for $1700 USD in the USA.
Here in Canada, from the dealer...I'm guessing it would've cost $3500 CAD.

M


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Thanks Tom for this guide! I was going to put on the Bezels you sent me and the battery died after 2 months in the storage - no power there at my spot :-(

One thing I would add to this thought which took me a while to figure out.
When connecting the 12V battery to the red fuser, the negative has to connect to a metal part of the car. However, seems the hinges are either insulated by the paint or the lubricants. I was not able to pop open the boot. Then I tried to connect the negative to the bolt (picture attached) and it worked!

Anyways, thought I’d share this.
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#6

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Tom
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Good call. I'll point that out in this post. In the PDF I posted below in the instructional section, it does mention this and says to attach the ground to the metal catch in the door jamb, since that's what the manual suggested iirc. This thing...
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Also, sorry that happened -- quite the nerve-racking pain I know....


#7

myjc
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Tom wrote: Wed Feb 16, 2022 6:31 pm Good call. I'll point that out in this post. In the PDF I posted below in the instructional section, it does mention this and says to attach the ground to the metal catch in the door jamb, since that's what the manual suggested iirc. This thing...

IMG_0260.jpg


Also, sorry that happened -- quite the nerve-racking pain I know....
Haha! There goes how carefully I read the guide and the user manual lol


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myjc
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Tom wrote: Wed Feb 16, 2022 6:31 pm Good call. I'll point that out in this post. In the PDF I posted below in the instructional section, it does mention this and says to attach the ground to the metal catch in the door jamb, since that's what the manual suggested iirc. This thing...

IMG_0260.jpg


Also, sorry that happened -- quite the nerve-racking pain I know....
I think the metal catch is a better place to connect the negative, much better grip


#9

Cowher
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Very helpful and well documented thanks I had a Porsche trickle charger on my 2021 911 Carrera S - but plugged into the passenger side "outlet" - which I have used on my previous 911s... I was not aware that this was no longer a working option on my new 992 !! I think it may actually have drained my battery instead of keeping it charged !?? Anyway - the dealer informed me of this change - so today I will give your instructions below a try.... wish me luck !
thanks Mel


#10

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