Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

12V Battery Problem

This site may earn commission on affiliate links.
I'm curious as well, my 12V AGM battery doesn't seem to charge beyond 13.7V but then again my 12V replacement warning has been on over the last 8 months/4K miles.I
I believe a fully charged AGM battery will read 12.85V, so it sounds like you are reading the charging voltage e.g. the car is not asleep?

 
The stock original replacement is about 175. Mine lasted 8 years. I don't see an ROI in a very expensive Lithium battery.
It seems by all the post on here, the 12 v battery is a crap shoot. I had to wait two months for mine. They r made in China, boat ride, distribution mess.
Help desk said 13v battery should be above 13.5 all the time. It runs entire car. Litterly the entire car. Only heater unit, Cooling compressor are 400 volts DC. Rest is 12v as a normal car. That is a lot of strain on that battery, but mine lasted 8 years.
 
  • Informative
Reactions: aerodyne
I had the same issue today. My 1 year old Model S had the 12v battery die in a parking garage. In the last 6 months I've had the glove box motor replaced, temp sensor replaced, and 6 months of nothing after paying for a winter wheel/tire package they said was in stock. With over 100 grand spent on my Model S, I think I'm done with Tesla

Latest updates allow you to access service mode in which you can see both 12V and HV pack stats and health.

I suggest you had a case of infant mortality on your 12V lion batt.

Avoid service if you can, sure to be a less than good experience.
 
Help desk said 13v battery should be above 13.5 all the time. It runs entire car. Litterly the entire car.

This is incorrect. The battery is not used when the car is awake, only when it is asleep at which time time the load on the battery is minimal. If you turn on Sentry, HVAC, charge the car, etc., the car wakes up. The DC-DC converter is what “runs the car” except for the motors and HVAC.
 
I believe a fully charged AGM battery will read 12.85V, so it sounds like you are reading the charging voltage e.g. the car is not asleep?

Yes. I'm reading it from my Anker battery monitor via the "cigarette lighter" port. Next time, I'll try the to measure with my multimeter from the remote battery posts behind the nosecone. My original 12V battery lasted over 4 years; this current one gave off "replace the low voltage battery" warning right at the 2 year mark. Our 2013 Fiat 500e with 84K miles on it is still on its original 12V battery.
 
Yes. I'm reading it from my Anker battery monitor via the "cigarette lighter" port. Next time, I'll try the to measure with my multimeter from the remote battery posts behind the nosecone. My original 12V battery lasted over 4 years; this current one gave off "replace the low voltage battery" warning right at the 2 year mark. Our 2013 Fiat 500e with 84K miles on it is still on its original 12V battery.

You got the idea, the outlet is only available when the car is awake and is powered via the DC-DC converter. But when you measure at the battery you will still need to ensure the car is asleep, otherwise, you will be reading the charging voltage.
 
  • Like
Reactions: maximizese
Picked up the car Monday morning. Tesla charged me $195 for diagnosis fee. They replaced the 12v battery at no charge (it was under warranty since they had just installed it 11 months ago). My only serious complaint is the fact that it took a week to get a 12v battery!
I’m always curious as to why Tesla charges a diagnostic fee when the issue found is related to an item under warranty.

I was told that if the problem is under warranty, then the diagnostic fee isn’t charged. So is this up to the SC’s discretion?
 
Hmm. I guess that means my default should be taking my car to Electrified garage vs the SC since my warranty only covers DU and battery. Both are about the same distance driving-wise since SC is technically closer but traffic is a pain most of the time.

Two different occasions, took me weeks to get a 12v, even when I paid for it.

Last time, showed up and they had none after a 45 min wait. Had to drive to a different SvC.

Really hard to understand why parts are such a problem.
 
Hmm. I guess that means my default should be taking my car to Electrified garage vs the SC since my warranty only covers DU and battery. Both are about the same distance driving-wise since SC is technically closer but traffic is a pain most of the time.
I would prefer Electrified Garage given that I have more reason to trust their work and insight. I've been flat-out lied to at Tesla SC 2 of 4 visits.
 
  • Like
Reactions: aerodyne
Stacklina. It's called greedy incompetent Service Center. According to post here, some do, some don't. Six years ago Jax SC did diagnosis over the air. FREE,. Sent me invoice for repair. Thanks folks ,. It was water pump number 2. Changed it for $50. They stopped doing that because us gearheads can fix the car without them. Just need to know what is bad. We can rent their entire diagnostic SW for $30 a day or $3000 a year. But it's hard to run. There is a YouTube video on it.
 
I’m always curious as to why Tesla charges a diagnostic fee when the issue found is related to an item under warranty.

I was told that if the problem is under warranty, then the diagnostic fee isn’t charged. So is this up to the SC’s discretion?
They told me they charge the diagnostic fee if they perform a diagnostic check, no matter what the issue turns out to be.
 
They told me they charge the diagnostic fee if they perform a diagnostic check, no matter what the issue turns out to be.
Yea, it seems like there are inconsistencies with this, much like everything when you visit a SC. There's no real continuity. Even something simple like the MCU 2 upgrade seemed to take multiple advisors input on how to input the cost into the estimate.
 
  • Like
Reactions: aerodyne
Yea, it seems like there are inconsistencies with this, much like everything when you visit a SC. There's no real continuity. Even something simple like the MCU 2 upgrade seemed to take multiple advisors input on how to input the cost into the estimate.
The other part that really bothered me was their refusal to offer me a loaner car, even though they admitted it was a warranty repair. I appealed to the SC manager, but he still refused. I was without my car for a full week, all because of a 12V battery.
 
The other part that really bothered me was their refusal to offer me a loaner car, even though they admitted it was a warranty repair. I appealed to the SC manager, but he still refused. I was without my car for a full week, all because of a 12V battery.

Loaners have been scarce for a while now. Make sure they credit you for Uber and towing.

Still awaiting reimbursement from Sept.

Just be glad they did not break anything...that you know of....
 
The other part that really bothered me was their refusal to offer me a loaner car, even though they admitted it was a warranty repair. I appealed to the SC manager, but he still refused. I was without my car for a full week, all because of a 12V battery.
Yea the loaner thing is very much up the advisor as well. I took mine in for low coolant warning, turned out to be just a valve issue but they did my MCU2 at the same time and sent me home with a loaner even though I'm waaaay out of warranty so I applaud them for making a decent impression my first visit but the advisors contradict each other constantly as you're handed off if yours happens to have a day off.

The thing is, why don't they just keep ordering 12v batteries and have them in stock? It's that a normal thing for a service operation? I feel like I need to keep one on hand now..
 
From my understanding, Tesla designed a system that uses the 12V system relatively extensively compared to ICE vehicles and other BEVs. Vehicles with theft deterrent systems, thermal management, internet connectivity, or remote access can experience quite a bit more "vampire drain." It's been long chronicled that Tesla has had issues with the demands of their 12V system and relied on auxiliary batteries that could handle the load and cycling without the need for a belt driven alternator. Many manufacturers seem to have similar problems while others do not. Our old 2007 Lexus Rx400h would predictably need a new 12V battery nearly every 2 years to the day (the tell was that the power windows would slow, lights would dim, and the multimeter would register <12.2V). VW has had issues with their 12V systems on their EVs as well:


Here are some random articles about the issues over the model years:





However, our 2013 Fiat 500e with 82K miles on it still has its original Mopar 12V battery...granted this battery is a rather large group 47.