12 Volt failure, Immobilization while driving, by Edmunds

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.

Captain_Zap | 20 février 2014

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.

KidDoc | 20 février 2014

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.

jbunn | 20 février 2014

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.

hillcountryfun | 20 février 2014

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...

J.T. | 20 février 2014

@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!

shop | 20 février 2014

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...

carolinagobo | 20 février 2014

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

shop | 20 février 2014

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.

nickjhowe | 20 février 2014

+1 @shop | 20 février 2014

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.

brandtlings | 20 février 2014

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... | 20 février 2014

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.

TeslaLandShark | 20 février 2014

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.

L8MDL | 20 février 2014

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"?

Pungoteague_Dave | 20 février 2014

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.

Pungoteague_Dave | 20 février 2014

@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.

Captain_Zap | 20 février 2014


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.

Mathew98 | 20 février 2014

@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.

Mark K | 20 février 2014

+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.

Mark K | 20 février 2014

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

triss1 | 20 février 2014

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.

brooklynrab | 20 février 2014

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.

Car t man | 20 février 2014

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..

AmpedUP | 20 février 2014

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.

AoneOne | 20 février 2014

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.

L8MDL | 20 février 2014

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?

Pungoteague_Dave | 20 février 2014

@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.

GeekEV | 20 février 2014

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

Koz | 21 février 2014

@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.

jkn | 21 février 2014

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.

NKYTA | 21 février 2014

Driving a 90's Subura at 75mph, in the left lane on Hwy 101, in traffic, my pistons (remember those?) seized. Most scary 20 seconds of my life attempting to get to the right lane and (fortunately) a downgrade exit.

All cars have instant issues, all I'm sayin'.

TeslaLandShark | 21 février 2014

I also had my alternator in my old ICE fail at night driving on highway 880 in Oakland in a spot where there was no shoulder. Thankfully I was able to reach a nearby exit and coast into a gas station parking lot before the car completely quit.

Pungoteague_Dave | 21 février 2014

ICE cars don't just stop when their alternators fail. Just sayin'. The battery will keep the car alive long enough to get it stopped safely unless the driver completely ignores all warning lights. And if an engine seizes, there's this thing called a clutch in a manual transmission car, or the shifter in an automatic transmission car. Any car can be immediately disengaged from its propulsion system. Which is why the claims of unintended acceleration in Toyotas are strange - the cop whose entire family was killed couldn't figure out how to stop the car from accelerating, but all he had to do was take it out of gear. We tend to freeze up in unfamiliar emergency situations.

Wonder how many Model S owners know the secret to turning it off in an emergency? Or how many steps it takes on the screen? Or are capable of remembering it when in a crisis?

rd2 | 21 février 2014

My old ICE BMW 'just stopped' multiple times due to various reasons. While driving. The battery did not, in fact, keep the car 'alive' long enough to get it stopped safely, unless you think the 5 seconds I had to pull to the side of the highway were long enough. So I disagree with Dave on this point. I'm not an ICE expert, but those experiences I remember quite well.

That being said, this episode sounds concerning, but it also seems exceedingly rare. I have over 25k miles in my S, and haven't had a single problem of significance. My 12V battery was replaced in November as part of the annual service. My S has gotten faster, smoother, quieter, and more capable with software updates and an annual service adjustment to the panoramic roof. My ICE only got worse with time.

I think Edmunds got a lemon, unfortunately. Hopefully Tesla learns to correct these errors, and few, if any, more lemons are produced.

AmpedRealtor | 21 février 2014

What happened to Edmund's concerns me very much. This could happen to any of us, with our friends or family in the car, and in a situation where an accident could result. This should not be acceptable under any circumstances, sorry.

I don't agree that just because this happens with ICE vehicles that it's okay for Model S. This is a clear weakness in the Model S design that could result in injury or death, should not be acceptable under any circumstances because Tesla can and should do better. Tesla has tried to exceed ICE cars in every way with Model S design, so I'm not quite sure why a design deficiency is deemed okay simply because the same may also happen to ICE cars. If we used ICE cars as our benchmark, we wouldn't even have EVs let alone Model S.

A weakness has been identified and should be addressed ASAP.

NKYTA | 21 février 2014

@PD, @AR - btw, I wasn't disagreeing that this needs attention, it certainly does. I was just sharing my anecdotal experience in an ICE. When you are in a large moving vehicle at speed, a lot of stuff can go wrong and cause injury, either ICE or MS.

I very well could have died and/or caused injury on 101 that day.

But, I am an exceptional driver.
;-p | 21 février 2014

Is this 1 out of 22,000 cars or something more frequent? No matter how well engineered an item is, things break, die or otherwise cause problems. If you're concerned about the Model S being an unsafe car - sell it, but I wouldn't recommend getting an ICE car or any car. Better not take a airplane ride either. If fact, sitting at home could kill, although rather rare.

We all live with risks. This seems blown way out of proportion. Serious yes - disconcerting maybe, will it hurt you, very unlikely.

Now most luxury ICE cars use electronic transmissions. While I've not tried it, I wonder if you can get these cars into neutral if the battery dies while driving. Of course if the transmission with it's hundreds of moving parts fails, no telling what happens or what you'll be able to do.

Lastly, Edmunds has documented burnouts, has pulled the car apart to look and photograph insides, and has put a lot of aggressive miles on their car. Perhaps they contributed to the problem. Sort of nice that Tesla has overlooked all this and covered all the repairs under warranty. I suspect most other car companies would say "Sorry, here's the bill".

AoneOne | 21 février 2014

From the article: "I simply had to coast to a stop on the onramp of a Los Angeles freeway, well after dark."

As I read it, the car was not stuck: it had no power, but it could have been pushed, if necessary, to move it to a safer nearby location.

The way many are responding to this made me wonder if the wheels had locked due to the battery failure. That would have been far worse, outside of the normally expected mode of failure, and certainly unacceptable.

Tesla could have included a redundant power system for the 12V, with diode isolation and separate charging paths. We do similar things in my industry (enterprise class storage servers), but that seems quite far beyond the normal levels of reliability, complexity, and cost expected for a car.

Brian H | 22 février 2014

Perhaps it's part of Edmunds' way of "testing to destruction", a time-honoured engineering principle.

jkn | 22 février 2014

He mentions that car was stuck: "we couldn't get the car out of gear." I guess gear selector went into 'P'. If ICE transmissions breaks situation could be same. In EV this should not happen because it is preventable.

12 V system could be made almost absolutely certain with minimal cost:
Every device in 12 V system should be protected by a fuse. 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. Only short in 12 V power cable could disable this quickly.

What really happened? Was there a short in power cable?

brooklynrab | 22 février 2014

This makes me think about the difficult balance tesla finds itself in, with regard to customer communication. More so than with a normal car company, we feel very proprietary about tesla, almost as if we own it (many of us do) and expect a level of communication and interaction with tesla as it hits its speed bumps and (hopefully) gets better. I'd love for them to issue a periodic statement about incidents like this, the 12v issue in general, why it happened, how they are engineering to make it better. But they would prefer not. They obviously don't want to focus people on the negative, or to talk much about deficiencies "to be fixed in the future", because that will lead to people putting off their purchases until these problems are fixed (I did that for a while, waiting for blind spot detection, which I believe will be out by summer, but couldn't wait any longer -- I'll pray that I can retrofit it when it comes).
So let's all keep our fingers crossed that Tesla, and hopefully Elon himself, are reading these postings and taking them in.

redacted | 22 février 2014

"Things happen with ICE cars, but not like this." @jkn is right. In an ICE even if the engine were to lock up you could still put it in neutral and take off the parking brake.

Since the Tesla doesn't have a gearbox with Park in it the problem here seems to have been that the car turned on the parking brake and it couldn't be turned off. Which gives you a rock in the middle of the road rather than something you can push off to the side.

"Sure this can happen to ICEs, I blew a rod" or whatever. Don't people read the original article and understand it? It seems clear as day.

J.T. | 22 février 2014

@Brooklynrab After I relearned how to set my side view mirrors I no longer had a blind spot to detect. Search for "How to adjust rear view mirrors" and you will see that blind spot detection is completely redundant.

AmpedRealtor | 22 février 2014

+1 jtodtman

Until I owned Model S, I didn't realize that I had my rear view mirrors adjusted incorrectly on all of my previous cars. Most people use the wrong metric by which to adjust their side view mirrors, leading to blind spot issues. Blind spot detection is absolutely unnecessary - the only reason the feature exists is because people don't know how to adjust their mirrors.

Here is a link to a simple instructional video, you may be surprised that you haven't been doing this all along:

Pungoteague_Dave | 22 février 2014

it is very clear that this is not one out of 22,000 or 30,000. All Tesla Model S vehicles have 12 volt batteries with this problem, either manifested already, or waiting to happen. These aren't lemons, it is a design flaw. Tesla has been doing a slow, unannounced recall to replace virtually all of the 12 volt batteries, along with changing a part of the wiring. MANY owners have already had three batteries. Virtually all will have them replaced at least once, and most twice, if and when Tesla can figure out the engineering problem.

As it stands right now, they acknowledge the problem, are trying various fixes, and are still working on it. Elon initially blamed the problem on a rash of improperly made batteries from a supplier. While he wasn't intentionally misleading, it does turn out that this was not true. TM eventually redesigned the entire 12 volt battery system and rolled out a replacement program with a different battery chemistry and monitoring system. That apparently has not worked well, and they are now trying to find another approach.

The two service centers that I have visited have huge inventories of three things: replacement 12 volt batteries, replacement high voltage batteries on stacked pallets to replace the main batteries on cars that have had 12-volt battery problems (these are sometimes related and apparently interact, creating "anomalies" in the main battery), and replacement motor/inverter assemblies. Replacement of these items with more recent designs is being reported regularly and constantly, and the design failures, couched as upgraded hardware, are well known and understood immediately at the Service Centers. This isn't some small thing to be brushed aside as just a few lemons or specific cars. It is inherent in the original design and is the process of being aggressively fixed.

Iowa92x | 22 février 2014

That's a little disturbing to hear service centers have stacks of replacement motors and inverters queued up. Expensive components there, what's the deal?

Agree the 12v battery issue persists, Tesla is trying and will eventually figure it out. Interesting that of all the hard engineering problems Tesla had to solve to build an electric car, a low tech lead acid is a thorn.

RedShift | 22 février 2014

I agree with P_D that the 12V battery dependency is a design flaw that is being addressed by Tesla.

On a side note: turning on the rear camera at night eliminates my blind spots. I have learned to place the car by looking at it's image on the screeen. Very useful for those with tinted windows, like me. During the day time, I dont need that, I just turn and check.

brooklynrab | 22 février 2014

Ampedrealtor and Jtodtman -- that mirror trick is cool. Why didn't they teach me that in driver's ed 35 years ago? Why am I learning it from a pimply faced kid now? thanks. | 22 février 2014

Everyone seems to think the Edmunds issue was the 12 V battery, when I didn't see anything about that being the cause. The 12 V battery was working after the car stopped and continued to run the emergency blinkers for 30 minutes.

The parking brake was energized when the car stopped (not clear if Edmunds put it in Park or not). When the main propulsion system is down should the parking brake be allowed to be released? I don't have an answer for that. I can see both reasons to override it and reasons not to. What if it was stopped on a hill (and most on-ramps are a hill), should it allow the parking brake to be released? The car might roll away and cause a far bigger problem!

Yes, they did replace the 12V battery when the car was repaired, but it was drained to zero keeping the emergency flashers going, not healthy for any battery. I'd expect the same in an ICE car - drain the battery to zero, then it should be replaced.

J.T. | 22 février 2014

@brooklynrab. I felt the same 6 months ago.