12 Volt failure, Immobilization while driving, by Edmunds

See this article by edmunds this morning as part of their long term Tesla ownership:
Basically, the 12v battery appears to have died with practically no warning while driving on the freeway, and they couldn't even put it in neutral to push off to the side of the road! I've read about 12 volt replacements on the boards, but never about a drive time failure. This is scary and dangerous, and is worrisome in terms of planning a road trip through decidedly non-tesla country. Has anyone had an issue like this? If they did and were on the road, did tesla take care of getting you back on the road if you were in mid-trip?
One of the things I really look forward to doing with this car is road tripping. Things happen with ICE cars, but not like this.

Of course things like this happen with ICE vehicles. I had a radiator fail and dump its contents. I had to coast to the side of the road. As a matter of fact, I had multiple failures in that car in different systems.

I wonder why they didn't get alerts to replace the battery. Did they miss a message or notification as the car changed hands internally? Did they miss an update?

I find it interesting that they bothered to release the article at earnings time without completing the article and telling the reader what the fix was and why the notifications failed.

I had an old ICE car that blew a waterpump and overheated in the middle of nowhere, this is nothing new but the lack of a warning is disturbing.

I had a brand new Ford Explorer only a month or two old. Driving up into the Snoqualamie Pass, the serpentine belt broke. Made a huge bang. Lost power steering, power brakes, and engine cooling. The car overheated after a minute, and needed to be put on a flat bed and taken to an autoparts center so I could get a belt and wrench set.

So these things do happen, even on a new car. The replacement belt lasted 200K and never failed again.

Edmunds tends to publish negative Tesla/EV articles...part of their package.

I was told that Tesla has switched to a deep cycle 12V battery from a much better supplier but I wonder what kind of monitoring features they have for that battery?

It seems like an owner should be able to go to a series of screens that display system status. One of those status' could be the 12V system. Could be useful...

@brooklynrab, You are right that these things don't happen to ICE cars if you mean to say that a 12 volt battery issue won't immobilize your ICE car while in motion. But look at all the moving parts that can go kablooey!

I've never ever liked how dependent the Model S is of the 12V battery. Even the much bigger 12V car battery that ICEs use is unreliable. The Model S 12V battery is puny by comparison. Relying on it working 100% of the time is nuts. IMHO, Tesla needs to redesign that entire part of the car...

Tesla should use Integrated Lithium Ion Battery-Ultracapacitor as a 12V battery, it won't fail, check the link.

That particular ultracapacitor/battery hybrid is the wrong physical shape (as I mentioned, the Model S 12V battery is very small in comparison to a typical ICE battery) and optimised for the wrong application. The Model S has a deep cycle battery instead.

BTW, it isn't clear that it was the 12V battery itself that failed in the Edmund case. It could be any number of other modules in the 12V charging system - it could be the DC-DC converter, for example.

But yes, a better 12V battery and 12V system overall is what is needed.

+1 @shop

Wow! You want to redesign the car over one reported failure! Yes, I suspect there may be a few more similar failures, but it's been rock solid reliable for me and every owner I've talked to.

All cars have critical components that should they fail, you'll be stuck. On an ICE car there are far more of these critical components - any one fails and you'll be dead on the road. It's sort of amazing how reliable ICE and EV cars are.

I've never seen a Model S on he side of the road (and we have a lot of them here in the Bay Area (CA). So many, it's rare to go out on short errand and not see at least one.

OK, this is ridiculous. Tesla notified me and had me schedule a ranger to replace the 12V battery in my S. Tell me they weren't monitoring Edmund's car. I don't believe it. Broder comes to mind...

I've found Edmunds to be on the level and quite reasonable. They report what happens, often good, and sometimes bad. I was impressed that of all the media outlets, they were the first to actually buy a Model S (even before Consumer Reports). They have also had very good things to say about the Model S.

While some users have gotten pro-active notices from Tesla to replace the battery, it's not even clear this was a battery issue. Since the warning lights worked for 30 minutes, it sounds like something else may have failed. For example if the contactor failed (which connects the high-voltage battery to everything else), you'll have no power and nothing to charge the 12v battery. Until we know more it's just speculation.

I've been following the Edmunds long term road test posts and I agree that they are reasonable. Unfortunately they've had more issues than probably most owners. I haven't had a single issue other than the proactive 12 volt battery replacement that Tesla did when I came in for service.

Once the car is diagnosed and fixed, Edmunds will do a follow up post and tell us all what the actual issue turned out to be.

The follow-up post is posted. Tesla replaced the main battery, the 12 volt battery, and the main drive (for the third time). Can you say "lemon"?

They did follow up and report that the high voltage battery, 12 volt battery and some other stuff had to be replaced. You conspiracy theorists need to re-think. Edmunds experience exactly tracks my own - They are on their third drive motor/inverter, like me, and have had their main battery and 12 volt batteries replaced, and have had the standard widespread maladies reported here, like the door handle design failure. I have had each of these issues, plus dozens more, all now fixed and the car is great.

They are huge fans of the car - no Brodering going on there. If you read the reporter's story, it was a scary experience. In many years of car ownership, I have never owned a car with so many fundamental and expensive repairs (my repairs now far exceed the original purchase price), and design-in-process issues. I have also never had a car so dramatically strand me like happened to the Edmunds reporter. No need to sweep anything under the rug when nothing happens. I still love the car, and am getting another, but lets stop trying to deny reality or suspect the timing on every report when it might affect your stock price.

@brantling - apparently the Tesla Motors alert system isn't 100%. My two 12-volt battery failures came without any call or knowledge from the mother ship. In one case, I was alerted while at home, in another, while in the middle of a long trip. In the first, they saw it in their remote diagnostics system only AFTER I called - then they could see it immediately. They sent a Ranger five hours each way to pick up the car (stranding me because they could not bring a loaner on the flatbed) and discovered a wide range of maladies, ultimately resulting in replacing the entire drive train, from both batteries, to the drive motor and inverter, to the brake rotors.

TM can't monitor and catch everything. And it does not make it intentional when a customer breaks down without seeing a warning notice, or if TM does not catch it in the monitoring systems. We're not all idiots. These things DO have a tendency to break down in certain ways and we are now seeing the trends in terms of which areas are prone to have issues, as well as the solutions. Unfortunately the solutions and redesigned parts are fundamental to the car, and very expensive to replace.


Did your 12v batteries fail before the update that added the warning feature that contacts the mother ship? That is a fairly recent addition within the last few months.

No conspiracy theory. Just pointing out reckless and incomplete "reporting" of half a story. It isn't journalism. A follow-up isn't enough. That is like a "correction" in a newspaper.
Not many people go back to re-read it or look for a follow-up.
No one has bothered to post it here either.

@PD - You were one of the few drafted beta testers that made the later production MS a better car. Be proud that you chose to stick with TM for addressing all your issues. Now you're an expert in most things MS and can share your vast experience with the rest of the owners.

You should be commented for having reactions vastly different than some who would thump on their chests and declare mutiny on the TM ship if anything go awry.

Thanks for sharing with us Dave.

+1 shop

As more than one us have posted before, the single-point-failure dependency on the 12V battery is not an optimal architecture.

A small, redundant backup cell, (maybe with deliberately different chemistry - like Li-Ion), with an automatic fail-over circuit, would be a wise upgrade to the architecture.

They can still preserve those cut-off intervention access point for first responders if the backup is integrated intelligently (which I'm confident Tesla would do).

Tesla was quick to recognize and act on the 14-50 plug heating risk, and went ahead and designed a thermal fuse in the plug head as some of us had also suggested as wise. That was a smart play by TM to protect customers even from faults outside Tesla's control. In my opinion, their fast-turnaround software then hardware upgrade responses to address this were stellar. Never seen anything as good from Mercedes or BMW.

Others please chime in, but there are already some of us who feel this 12V vulnerability is a tier 1 issue to protect the great reputation of the car, and should be phased in as soon as practical.

All of this said, people should realize that gasoline cars have much more single point failure nodes and a higher risk of power loss during driving than a Model S.

Even with the current design as it is now, the car is way more reliable than the gas alternatives.

Adding a backup system is good idea that's about making the best design even better.

PD's comments here are totally fair, and the most compelling comment was his action - buying more of these cars.

Does anyone know if a 12v battery plugged into the cigarette-lighter power socket would solve the issue of a failed 12v battery? There are a number of devices on Amazon that are designed as emergency starters for ICE cars that can plug into a lighter socket (like the Clore ES5000) and power a car while the battery is removed.

To the uncritical Tesla fanboys -- Edmunds has been fair to the MS in its postings, in my opinion. This is scary -- to have the car die right in the middle of the road. Sure things happen with other cars, but that doesn't make this any better. I literally got my "finalize order" email today, so this incident was jarring to read. I know Tesla will make it right and is still learning. Superb customer service is the reason so many of you took the early plunge, and I will now, but they MUST make this a priority. Sure, I'd really like blind spot detectors ASAP and I'd like my IPhone's music interface to work as well with a Tesla as it will with a Jeep (and for all those Apple rumors....), but this 12V battery is mission critical. At least add a monitor function so you know when that battery, literally the heart of the car, is fading.

Tesla, find a simple workaround for the 12 battery. If not for more poised approach, two separate smaller 12 batteries..

Anything but this. So no one gets strangled by a lame old 12v lead acid
batt failiure. And make it a lithium battery, while at it..

For those who want to attack Edmunds in any way, please read their posts before doing so. In my opinion, they have been extremely fair. I'm confident a fix can be created for the dependence on the 12V battery, but this failure was larger. I recall reading last week about another main battery failure that involved the primary relay. I hope that we're not looking at some sort of systemic main battery problem. 'Sure curious as to the vintage of the Edmunds car...especially whether they have an "A" or "B" battery pack.

If the 12V battery fails shorted, which can happen suddenly, any car, ICE or Model S, might stop dead in it's tracks. The short prevents the alternator or power converter from keeping the 12V available and so most of the car electronics will cease operation.

My main concern with this failure was the fact that apparently Edmund's could not move the car after it stopped. On a major highway, after dark. Then the flashers failed. I have never seen that problem with an ice vehicle - just put it in neutral and push it off the road. A non-movable car, in a lane of traffic, unable to be moved by the driver, is NOT ACCEPTABLE,PERIOD! Did the driver not know some procedure for getting the car to a neutral position in order to push it - or is it not possible due to some type of electronic gear lock?

@captainzap, you apparently are either unawares re of how Edmunds operates or chose to not read their Tesla pieces. They don't write full articles on cars that they own and evaluate over time. They essentially blog experiences as they occur. When the car broke down without warning, they reported that immediately, fairly and without analysis or opinion. When the car was taken in, they reported that immediately. When the car was repaired, they reported that, with some added analysis, giving Tesla a break for how this played out. They did nothing more or less in any of their pieces on the Tesla, and they were not irresponsible, reckless, or incomplete in any way. They simply reported the facts that they knew when they knew them. They do not owe you or Tesla anything. Their threads on the car are sequential and you can go back and forth through the history of their ownership. In my opinion they bent over backward to be fair when bad things happened. Please read before reaching conclusions and making uninformed comments.

To answer your question, there was no new call-home feature added to the car recently according to the Rockville SC. It was always there as part of the car's overall self-aware systems monitoring software. I had other unrelated alerts that did make it back to Fremont last May. My car experienced both an early and a late 12 volt battery failure, and now needs a third, none found proactively by Tesla. One of my homes is in an area with no cell phone service, so that could be a factor. Further, many people park in underground garages where no communication can occur. My car often spends a day in underground garages in Baltimore and DC. Remote monitoring is not close to being a fool-proof system, especially for safety-related functions like this one.

WRT to the new 12v batteries, I had mine replaced and the service paperwork said the new one was an Excide.

@Aone One

Exactly and an alternator failure itself will kill the battery on a modern ICE while underway. It happened to me in an Audi 90. Alternator died, battery depletes then dies. Once an ICE battery dies on a modern car, all electronics go including electronic control of the engine, power steering, dashboard, etc.

My thoughts:
Every device in 12 V system should be protected by a fuse. System has two power sources: battery and DC-DC converter. Converter should be connected through a diode, so short in it does not immediately deplete battery. Battery should be connected with a fuse. Converter must have enough extra power to blow this fuse.

If battery breaks, then car operates normally, but cannot be started.
If converter breaks, car operates normally until battery is depleted.
If something else breaks, fuse blows and only one system is dead.

I guess Tesla does not use lithium in 12 V system, because it burns when crushed.

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