12 volt battery failure

12 volt battery failure

So it happened to me yesterday. I was on the way to work and I got a "12 volt battery failure" error message, then "your car needs service", then "pull over safely". Only thing is, it happened so fast in like 10-15 secs I had no time to do anything before the car shut itself down and I was at a standstill. It was rather embarrassing - I was blocking traffic out of the parking lot and I had to direct traffic around my car. Fortunately the local service center sent over a guy with a car for me. And the service guy let me go off to work while he waited for the tow service. But I'm traumatized by the whole experience. I'm a physician and I had to get to the emergency room, but I had absolutely no warning and the car just shutdown. It could have been in the middle of traffic on the freeway or in the middle of an intersection. What's likely the problem? Did my battery fail?

Thomas N. | 03. juli 2014

I've heard and read about many 12v battery failures on the Model S. Most of those happened to the very early cars due to an out of spec lot of batteries that have since been sourced from another manufacturer.

I've heard of a few failures since then but most have been proacively identified by Tesla and replaced before anything happened.

Your situation does sound frightening. I wouldn't be happy if that happened to my wife on the freeway - especially if we had to be someplace. It's akin to breaking a belt on an ICE which has happened to me one time.

Please let us know what Tesla says about this incident.

J.T. | 03. juli 2014

@alang As Thomas N said the 12 volt issue is usually resolved proactively, mine was. My car's VIN was 12192, and many in that batch either failed or were replaced as soon as possible. So, I'm curious what your VIN is to see if it's another batch problem that Tesla isn't aware of.

Sorry for your frustration.

Captain_Zap | 03. juli 2014

Be sure that your contact information with Tesla is up to date and check to make sure that Tesla e-mail is not going to your junk mail file. (I had that happen.)

Tesla has contacted me proactively for 12V replacements. There hasn't been any problems since my replacement about almost a year ago.

nickjhowe | 03. juli 2014

+1 JT
@alang - Sorry to hear about your problem. what's your VIN? Do you have an older car?

minervo.florida | 03. juli 2014

This really concerns me as a safety issue.

Maybe we need to talk to Tesla about this, car shutting down in just such a short time could be very dangerous at speed.

carlk | 03. juli 2014

I'm sure Tesla have more data, including what actually has or has not happened, than any of us do.

dr_gko | 03. juli 2014

I have an older car, VIN 4295 with more than 25K miles on it. Had my 12V replaced a year after delivery, if I remember correctly. Last week I got 2 warnings that my 12V is low, in a span of a few days. Took it to Bellevue service center and this is what they found:

Concern: Alert appeared: "12V battery power low, car may shut down unexpectedly"
Pay Type: Warranty
Corrections: 12V Battery & Fuses General Diagnosis
Found alert for DC/DC not communicating, determind with logs the DC/DC is faulty.
Corrections: DC-DC Converter - 1st Generation
Replaced DC/DC Converter
Part Quantity
12V BATTERY (1024463-00-A) 1
Parts Replaced or Added

jordanrichard | 03. juli 2014

To the OP and any others posting problems, it is very helpful to others to list your VIN. As it has been stated the "early cars" had 12v battery issues. However, there is no clear definition of what an "early car" is. Mine is 32897 and thus far I have had no issues other than minor software glitches that caused phantom reboots, but those problems went away with further updates.

hamer | 03. juli 2014

Mine is 8808, and I got a 12 volt battery message while on the way to the airport on a trip. I called Tesla and they said to leave it at the airport and bring it to them when I got back. I did, and they replaced the battery quickly. I don't know if that makes me an early VIN.

SCCRENDO | 03. juli 2014

My vin is 77xx and got a proactive 12V battery replacement at 25000 miles

AmpedRealtor | 03. juli 2014

VIN 16186 - no 12v issues and no proactive replacements needed.

JPPTM | 03. juli 2014

VIN P09667--proactive replacement in May at 12k miles.

PBEndo | 03. juli 2014

I had a virtually identical scenario happen - little time to pull over and I ended up blocking a parking lot entrance. Though I had the 12v battery alert, it ended up being the main battery (85kwh), not the 12V battery. When the main battery goes bad, you can get an alert about the 12V since it is charged from the main battery. I also had a loaner on the scene in 25 minutes and the driver waited for the tow truck so I could go on my way.

Captain_Zap | 03. juli 2014

I think the OP's car is over a year old.

dglauz | 03. juli 2014

my VIN 11298, 12 V battery was replaced with no sign of problems.

My guess as to why you were able to be shut down at the driveway and block traffic is the car figured you had followed instructions and were now safely not moving, so it could shut down. Inconvenient that the car did not know that you were stopped in the middle of a traffic lane. :\

nickjhowe | 03. juli 2014

@dr_gko - ah ha!!

There were always two battery problems - one was the bad batch of batteries; the other is the DC-DC converter. Looks like there might be issues with the 1st gen DC-DC converter that happen sporadically.

@alang - maybe you were a victim of that. The surprising thing is you didn't get more warning - from the car or from Tesla. They've been pretty good at proactively alerting owners to 12V problems.

johncrab | 03. juli 2014

If it's any consolation, this same thing happened with my first Prius but it did not give me any warning. I started up fine, drove to work and when I wanted to go home, nada. The car would not even unlock. I could get in with the manual key but then had to crawl to the back to release the hatch manually do the 12v could be jumped. It was also from a bad batch and was replaced under warranty. At the 3 year point an Optima replacement was available and I installed one myself and never looked back. I'd like to see an Optima for the Model S because it is a superior battery. | 03. juli 2014

@minervo.florida "This really concerns me as a safety issue."

This is valid, but seems to be a rare occurrence. I've had two different ICE cars die while driving before (one actually caught fire while driving). These were both relatively new cars that were well maintained. I never got any warnings from these cars until it happened.

So my take away is any car can die while driving due to a huge number of reasons. The Tesla has a lot fewer of these reasons, and it's nice that it at least warns you and let's you stop while under control.

Lessmog | 03. juli 2014

Re: belt in an ICE
I had annual service done on my aging Saab a couple years back, including the aux belt. After less than 1000 km the belt suddenly erupted into little black strips and all the warnings came on. Fortunately, I had just stopped for a red light on a four lane street with a bus stop right beyond the traffic lights. Confirmed the damage and drove on to dinner with Daughter. (Had made a detour to visit ancient Mother.) Driving much harder due to lack of servo for steering and brakes, and also for having to also override the servo with my servo-weakened muscle power, while battery not charging. Although this was Sunday evening, Daughter meanwhile chased up a local garage to have car fixed next day, and lent me her car if I drove her to work. (I had a dentist appointment early Monday.)

Moral: The less moving parts in a car the better. Anything can break and it will, at the least suitable moment.

But I'll never revisit the garage that charged me for the bad belt.

alang | 03. juli 2014

Ok- I got the verdict back from tesla service center. FYI: My vin number P12164, I have car for about 9 months now, only 13k miles Battery was replaced today due to contactor failure. I confirmed that they really had to give me a new battery to efficiently fix problem. Original error code I saw: 12 v battery failure.

So what's the bottom line as far as my car? Is my vin number suggestive of an older car? It was a demo car with about 3k miles when I purchased. Shipped out to New Jersey from California store.

Is my problem like some of the other guys above? Really freaks me out- no warning at all -system shutdown on road blocking traffic.

donaldmeacham1 | 03. juli 2014

VIN 26001 so far no warnings and no 12v battery issues.

J.T. | 03. juli 2014

@alang You're vin and mine are only 28 away. My 12 v was switched out when they replaced my charge port for a malfunction. Yours was overdue to be switched and due to the nature of your purchase you might have fallen through the cracks. Hopefully, your problems are behind you.

alang | 03. juli 2014

After reading some of the posts above, I just wanted to add -

I just had my car serviced for the 12K annual checkup last month and nobody advised me that the 12V should be proactively replaced. My email address is current and I would have gladly had them replace the part proactively if they had asked.

But bottom line, is my problem solved? Do I have to worry that the model s has this flaw that can happen again at any time with little or no warning?

SCCRENDO | 03. juli 2014

Most of us did not have any problem to start and the 12V was just swapped out at a service because of the vin. Apparently the newer batteries are better. So far no problems with the new battery 14000 miles later. However I don't see this as a guarantee. | 03. juli 2014

The OP found out the 12V battery was fine (even though the error message indicated a 12V battery problem). It was the contactor in the main battery pack. The contactor connects and disconnects the high voltage between the pack and the car. So actually no batteries had failed. Since the contactor resides inside the main battery pack, so service just replaces the entire pack. Through the forums, I've heard of a few other similar instances, but it seems quite rare. Not something I'd be concerned about.

minervo.florida | 04. juli 2014

You might be concerned if your wife was driving with the grandchildren on the freeway and it just shut down with little or no warning.

That is my only concern.

J.T. | 04. juli 2014

@minervo I'm always concerned when my wife and kids are driving. But I'd be less concerned if they were driving a Tesla.

PBEndo | 04. juli 2014

Can you confirm that they replaced the MAIN battery pack, not the 12V? Your post is vague in regard to which battery was replaced, though I agree with TeslaTap, it sounds like the main battery pack. If so, your experience is almost identical to mine.

PBEndo | 04. juli 2014

Also, did you get a new or remanufactured battery? And which version?

alang | 04. juli 2014

General HV battery pack replaced due to contactor failure. I was told it was a new battery. Silver lining: battery power definitely more robust, range 5 miles greater for same 80% charge. This would appear to be from the new battery. I guess nothing to complain about

PBEndo | 04. juli 2014

If you look at the sticker on the battery (behind passenger side front tire) it will show version and if it is remanufactured.

I also had improved range since my original battery had 25K miles and a daily charge (90%) was down to 218-220.

All things considered, I was impressed with the service. Tesla took a problem and made it a positive experience for me.

AndyO | 04. juli 2014

I had tried to find my battery label several times with no luck. When having new wheels put on at an independent high-end car repair place, I was able to get under the car and hunt. The decal was rolled up between the battery and the side frame in a 1/8" crack. I pulled it out and scanned it for future reference. I didn't want it to fall off. I keep a copy in my glove box.

PBEndo | 05. juli 2014

AndyO - If that sticker ends in B,C or D, you might be able to sell it to an A owner;)

lhaase | 05. juli 2014

I just had this happen to me yesterday, and my car is only 40 days old with 1,100 miles. VIN 41932. Same warning messages with no time and the car shutoff. Had to be towed. Still waiting for Tesla's response/service center to come get it, which will apparently be Monday. I had a 2013 Model S for 15 months and never had this happen. This one is a brand new P85 and this was frustrating to have happen 100 miles from home on July 4.

PBEndo | 05. juli 2014

For anybody that has this happen to them:
Initially I had several alerts, the shutdown warning and my car stopped responding to the go pedal. After coasting into a parking lot, I pushed it myself into a parking spot to get it out of the way. It is surprisingly easy to push given its weight, but remember you have to put it in Tow mode if there is no one in the driver's seat.

I spent 10-15 minutes outside the car on the phone with Fremont, the local service center, and my wife making arrangements for the tow. When I got back in the car I noticed that the alerts all cleared and the car was functioning as if nothing ever happened. Throughout the entire event, the car never "shutdown" - the dash stayed on, the A/C was running, etc. After the alerts cleared, I could drive in both forward and reverse. I may have been able to continue driving all the way home, but I didn't want to risk it stopping again in a worse location.

So if this happens and you stop in an inconvenient/dangerous location, the car may be driveable again in a few minutes. This may allow you to move it to a safer location while waiting for the tow.

Tesltoronto | 05. juli 2014

lhaase: you have got me worried now. My VIN is very close to yours. Am curious to know what Tesla says about this. Is it another 12V battery recall? | 05. juli 2014

@Tesltoronto - This has nothing to do with the 12V battery. The contactor is a safety device to disconnect the high-voltage battery and is required by law (although Toyota is trying to get around it on their fuel cell vehicles). This is a mechanical device, and while quite reliable, if it fails - you'll have no power for the primary motor and the HVAC. The rest of the car will operate off the 12v battery - and is why the displays still work, assisted steering and assisted brakes operate, etc.

I can imagine a bad contactor might drop out if it jarred (i.e. pothole), but may also reconnect. It's bad so it may not fail completely or it may never connect again. I agree the best is to have Tesla fix it rather than trust it's not going to drop out again. It does mean the primary battery pack needs replacement, as the contactor resides in the pack (again for safety reasons). | 05. juli 2014

@alang - Perhaps the title should be changed, since the problem is a contactor and not the 12v battery? Perhaps "Contactor failure (resolved)". Might also be nice to make it private too.

You can edit your message by clicking on edit near the top-left (only you get this option).

jacobp | 05. juli 2014

I had the same problem as the OP. My VIN is 22590. I took delivery in late October 2013. My car was parked underground in my office parking garage at the time of the incident. After work at around 6pm, I came out to the car and it would not start. I got the 12v battery message and the message to pull over.

I called the Rockville, MD SC and they said they couldn't connect to the car and pull the logs since the car was underground in the parking garage. So, they sent out a ranger who replaced the 12v battery. I asked him if i had the old or new style battery and he said that my car had the new style battery. He said that while the new style battery is better than the original battery, there have been some failures, like the one i experienced.

He said that once i moved the car out of the parking garage he would pull the logs and get back to me. He called later in the evening and told me that the logs (which apparently are stored in the car (I did not know that)) showed that the alert occurred at 3pm and then again at 4:30pm. Because the car was underground, it could not communicate that info to the mothership, so nothing could be done proactively. I have confirmed that the DC-DC converter is fine (ie no alerts were generated for that).

It sounds like the OP's car was also in a parking garage when he saw his alerts. I'd suggest you contact your SC and ask them to pull the logs to see when the car generated all of the alerts. It may be that earlier alerts were generated while the car was in the parking garage that could not be communicated to your SC because you were out of communication access.


Tesltoronto | 05. juli 2014

Teslatap - How did you determine it is the contactors and not the 12V battery? Just curious. It looks like, from jacobp's post, that it is the 12V battery. | 05. juli 2014

@Tesltoronto - The OP is alang not Jacob. Alang stated in an additional post in this same thread it wasn't the 12v battery but the contactor. Seems like everyone reads the title and thinks that was the problem, even though he clearly stated it was only the warning message. I'm not saying users haven't had problems with the 12v battery, but the thread sort of derailed from the original OP's post and later statements.

lhaase | 05. juli 2014

@TeslToronto, a ranger is on their way to grab the car, but they haven't told me much of anything yet. Hope to know more after the collect and fix and return the vehicle. All service folks have been very efficient and helpful, but none apologetic nor very knowledgeable about the 12V battery/contactor issue(s).

lhaase | 07. juli 2014

I suppose I should wait for the final verdict from service, but I believe at this point it WAS the 12V battery, as the displays did not function at all and would not function even after a "jump" of the battery by the service guy, who added that he has seen this happen with "several" Model S 12V batteries. I asked about the 'contactor' and said he was pretty sure it was the 12V battery that had failed. I will know more when I receive my car back. | 07. juli 2014

@lhaase - Sorry about the problems you've had. Hopefully you'll get the car back shortly. You're right that your car sounds like either the 12V battery, a primary 12V fuse, or the DC to DC charger died.

I'm surmising the DC to DC charger might die in a way to kill the 12 v battery, similar to a alternator with shorted diodes that may kill the 12 v battery in ICE cars. In this case, a jump will not work at all.

Let us know what you find out.

lhaase | 08. juli 2014

@TeslaTap, you were right. I just got notification. Here's what they said after reviewing my vehicle:

"It seems there may have been a miscommunication regarding the problem with the Model S. Originally, the car told you that the 12v was low on power and could shut down, correct? We found that this was caused by an internal fault in the high voltage battery. When the fault occurred it caused the 12v battery to lose support and that's when you saw the alert. The main contactor on the battery is not working properly.

We had a new high voltage battery shipped on Monday and it is slated to be delivered tomorrow."


J.T. | 08. juli 2014

@lhaase Thanks for keeping us up to date. Hope your issues are few and far apart when you get your car back.

N300pg | 21. juli 2014

Had the same issue. A shutdown while driving, stopped on the side, put in park and drive again, it was ok. Next morning car wouldnt start, Tesla towed it, told me they are replacing the contactor on the battery. Car has 6000 miles.

jai9001 | 21. juli 2014

I just had my 12volt battery replaced today. VIN #099xx.

Symptom: car wouldn't go into sleep mode because it was constantly charging the 12volt with substantial increase in vampire drain.

jordanrichard | 21. juli 2014

VIN 32897, 6,800 miles, knocking on wood, no battery issues.

ben | 14. oktober 2017

I've just had a similar problem.

My car just broke down. It stopped working altogether. I got a message that said the 12 volt battery is not charged. And to contact Tesla Service immediately. I had to walk home and leave my car at a restaurant, taking my ten-year-old son home with me! Not cool. The car was just charged and has nearly 200 miles of charge in it.
The error messages said
• Acceleration reduced
• Car needs
• Service
• 12V power low
• Car may not restart
• Unable to drive
• Etc

I just took this car in for service a few days ago. And I fully-charged it 2 days ago. I’ve read that this could be due to “faulty contactors in the battery pack.” See Any idea what is happening here?