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Short lived 12v battery?

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I had also posted my concerns under the model S heading, but I am interested in getting a more local perspective on the expected 12v battery life. I have a model S 85D with 100000Km. First battery went at 65000km, 4 1/4 years. Second one just went at 100000k, 2 1/2 years later. Seems a little short considering our relatively mild climate. Also this is my daily driver, no sitting around collecting dust in the garage. Of note, I did have the MCU2 update during the last battery, maybe more strain.
Any comments from you "classic" driving tesla?
 
in the first week in 2018 I got a battery error. Battery was replaced so still on the replaced 2018 battery @94000km ( This is in contrast to my Kia Soul EV 2019 which at 45000km needed a new one. Seems to be a problem with Kia. )
 
Funny thing, when the car flags the 12v as needing replacement, software updates cannot be done. The car keeps prompting me to complete the update, then stops, saying the 12v needs attention. Kinda annoying until I get it replaced. The ranger cost for the battery has not changed since the last time 2.5yrs ago, but the labour/diagnostic fee has gone up.
 
when the car flags the 12v as needing replacement, software updates cannot be done


During the software update, the DC-to-DC converter shuts off for part of the time. There is a decent load on the 12V battery during this time. If the battery is weak, it could crash the computers in the middle of the update, which could be rather bad.

When my FSD computer was replaced by mobile service, he hooked a 12V car battery charger to my battery during the update, as it is a longer process, to ensure the 12V battery wouldn't be drained. You could do the same.

You can clear the battery fault by power cycling everything (pulling the connector under the back seat, and disconnecting the 12V battery). The fault will clear after that. Of course if the 12V battery is really bad, it won't fix that.