Is 12V dead battery issue tied to PMCC and using profiles and timers?

rbt3

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I have had the dreaded 12V dead battery issue happen to my 4S, and the dealer took my PMCC and deleted all profiles and timers and told me not to use them as the communication between the car and the PMCC may have caused the problem? I have done what they said since the issue occurred and have not had any problems since. I am not happy about not being able to use the timers or set up home and trip profiles in my car/PMCC though and wondered if anyone else knows more about this 12V battery issue? I currently have a general charging setting that charges as soon as I plug in to 85% as my only charge profile. I just hit the "direct charging" button to immediately charge to 100% for longer road trips. My electric rates like most of yours are lower between 11pm and 6am, so I previously set my timer to charge at those times, but have been unable to do that per the dealer instructions. I was also told to use the phone app very little as it may have had something to do with my dead 12V battery? Anyone really know the causes and fixes? Thanks.
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daveo4EV

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@rbt3 the 12V problem can still happen with or without profiles/timers and app usage, but use of those items increases the chances you'll encounter the problem.

there is no one thing you can do to avoid the problem - but avoid use of certain "features" lowers the chance the problem will occur, but does not change the probability to zero.
 
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rbt3

rbt3

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Read this Bulletin: https://static.nhtsa.gov/odi/tsbs/2020/MC-10185117-0001.pdf

Your dealer followed the recommendations described there.
Thanks ChrisK, exactly what my dealer was telling me, wonder why they didn't give me this bulletin info.? It would have made me understand what was going on a little more. I guess I'll keep charging as I do currently, no problems since I stopped using profiles and timers. I use the app still to check the charge, etc. but I log off after using it every time now.
 

mikeyyn

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Thanks ChrisK, exactly what my dealer was telling me, wonder why they didn't give me this bulletin info.? It would have made me understand what was going on a little more. I guess I'll keep charging as I do currently, no problems since I stopped using profiles and timers. I use the app still to check the charge, etc. but I log off after using it every time now.
I may be completely misunderstanding how iPhone apps use use ‘Background App Refresh‘ but could this working in the background affect the car? If the app is constantly seeking info from the car for example. I might be totally wrong, don’t know. Maybe one of our tech gurus will know.
 

NC_Taycan

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First, your car has a low-power always-on cellular radio. By always on I mean it checks in periodically (seems to be about every 60-90 seconds). That check in sends telematics status (state of charge, GPS location, tire pressure, mileage, doors status, parking brake status, lock status). By low power I mean this radio can probably run for a year on the 12V battery. It also checks if there is anything that needs to be received by the larger PCM computer (and wakes it up if so). This is in your OTA module. Actively using the Connect app ONLY to check on things does not wake up the car. Same with background app refresh. Summary - no need to disable background app refresh or uninstall the app.

Second, the cause of 12V death while connected to a charger seems to be related the car and charger attempting to communicate but failing. Examples - car is done charging but charger doesn't shut off pilot connection; changing a timer or profile while the car is connected; Something causing the charger to re-activate the pilot signal when the car is done charging. The steps in the bulletin are like a big hammer for a little nail. They likely help, but you can help by doing less. Continue using your timers and profiles as you see fit but don't change anything while the car is plugged in, and unplug as soon as possible after charging, and keep the key fob out of range of the car.

I'll save Daveo4EV the trouble of pointing out that the above *might* help but are *not* guaranteed to prevent the problem.
 
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