Model 3 completed dead in my garage. 12v the issue? Mobile service can’t come for a WEEK! what should I do?

[brkaus]

Just an update, last night I completely removed the 12v battery from the car. There was a strong smell of sulfur in the garage and the 12v battery had bulging sides and was hot to the touch in areas.

Definitely a failure . I had an ups that failed like that…. So hot I couldn’t touch it.

Tesla might want to check the charging system if under warranty. But it’s probably just a battery failure.

 

[brkaus]

Im still surprised it popped the frunk from the app. Good to know!

 

[stopcrazypp]

Just an update, last night I completely removed the 12v battery from the car. There was a strong smell of sulfur in the garage and the 12v battery had bulging sides and was hot to the touch in areas.

Cheapest option if you are out of warranty is to buy a 12V battery from Tesla for $85 at a SC. No third party battery as far as I know is that inexpensive for the given size, especially if looking for one with a vent hose port.

 

[Tronguy]

Not that I'm doubting the possibility of a dead battery, from your description. Heck, some years back I helped the lady of a family that we were good friends with Save Her Vehicle: The battery had actually cracked, spreading leaking battery acid over everything. Once I realized what had happened, I got her to find some of those rubber gloves one has below the kitchen sink, found some big-ass pliers that they had around, loosened and removed the terminals, and moved the battery, very carefully, up and out of the car and onto the driveway somewhere.

We then got out a garden hose and rinsed the heck out of the engine compartment for some 20 minutes, attempting to remove all traces of the acid from the car, then turned it on the cracked battery, likewise. Concentrated surfuric acid is nasty stuff. Not only will it go through a lot of materials, leaving holes behind, it'll do the same to you.

However, as in all things of this nature, there's still Other Possibilities. As I said before, batteries up and die on their own all the time. But, just to be persnickety, imagine that the battery charger circuit (DC->DC converter and all) is overcharging the battery. Real battery chargers are control circuits: They monitor the voltage of the battery. If it's too low, more current in. Too high, less current to No Current in. That feedback circuit involves components, wires, probably integrated circuits, and all that jazz. And, speaking as a EE who's done reliability engineering from time to time for a living, I can tell you officially, "Everything Breaks Eventually. Only the probabilities vary."

A seriously overcharged battery can, yes, fail catastrophically. After replacing the battery, I'd still chok the car over to a reputable, We Can Check The Tesla place, to verify all is sweetness and light.

Safety first.

 

[ethanfl79]

I just picked up the battery from the Tesla Service Center (tip: The parts department closes 1 hour before the actual service center).

Took it home, swapped it in, and the car now works perfectly.

Only $90 after tax!

Thanks for the help everyone!

 

[father_of_6]

Excellent!

Thanks for the heads up about the parts department... I'll likely be making the same run within the next year.

 

[AZAV8R]

My understanding is that all 12V stuff is powered by the 12V battery, as in, the "-" terminal is connected to ground, the "+" terminal is connected to 12V, and everything that's powered by 12V is connected to that "+" terminal. But that's not the only thing on that bus.

The architecture of the 12V battery circuit is bog-standard. In an ICE, the alternator in the car feeds a rectifier/charger that is also connected to the 12V bus. When the ICE is running, it spins the alternator which more-or-less keeps the 12V battery charged up. So, say that on this hypothetical ICE that we're talking about the 12V bus is using, say, 20A or something. When the car gets turned on (first click on the key) the battery supplies 20A plus whatever the starter motor needs to turn the engine over, thus discharging the battery a bit. When the engine starts, the alternator starts doing its thing, recharges the battery, and then, as the car is driven around town, supplies roughly 20A to the 12V bus both to keep the battery charged and keep everything else running.

Just so we're clear on this: If the alternator in the above scenario fails, it's possible to make it some distance down the road with the battery supplying 20A, so one can make it to a service center before the battery runs out of charge again and goes kaput. (Various shade tree mechanics have discovered this over the eons.)

On a Tesla, it's not much different. Instead of an alternator, there's a DC->DC converter that goes from the HV battery to the 12V bus and keeps the battery charged, as well as providing operating current.

What I don't know is whether or not that DC->DC is available at all times or if the car has to be some species of "on" in order for it to work. I suspect the latter.

Now, lead acid batteries can fail in interesting ways. A lead-acid battery's cell generates around 2V; six of them in series gives one the nominal 12V that people expect. (Fully charged, around 13 or so; fully discharged, 11 or so). Say that one one discharges the battery so it's in danger of going flat. (With an ICE, this is called, "leaving the lights on when one didn't mean to."

The six cells don't typically have exactly the same charge, there being manufacturing variations. At some point, then, one of the cells will become completely discharged while the rest are working. The voltage across this cell becomes flipped. If, at this point, one starts charging the battery again, that, "flipped" cell may not recover. So, instead of having a 12V battery, one has a 10V battery. There are a significant bunches of electronics that are designed for 12V and Won't Work at 10. Or will barely work. And if more than once cell gets flipped, that's all she wrote, you got 8V.

Thing is, as lead-acid batteries age, one of the things that happens is that individual cells can develop defects that cause them to self-discharge. You can see where this is going, a dead battery out of the blue. So, measuring the voltage across the battery is a Good First Step to make sure that it's the bus voltage that's messed up and not something else, like, say, a blown fuse.

However, there's a bit more than that. In the case of an ICE, a smart mechanic snags one of these multi-testers on a cart that repair shops keep around for this purpose and verifies that the charging circuit is running correctly. There's fuses on that charging circuit; dead alternators, due to bad or loose belts or just busted diodes, burned windings, and so on are Things. So, the first guess that the problem is a dead battery is generally a good one (and pretty common), but it's not the only thing that can happen. In fact, putting in a nice, fresh battery with a dead charging circuit will get one some miles down the road and the blame thing will simply fail again. Murphy says it will be in The Middle Of Nowhere, rather than, say, in your garage.

Again, a Tesla isn't much different, except that if the charging circuit is a goner, there are many possible causes, just like the ICE, but, of course, different ones. The DC->DC might be dead; I've heard of loose wires (!); and if the Pyro Fuze is gone, well, ain't got no HV in that case to charge that 12V battery.

To the OP: There's Request Service, and there's Roadside Assistance. The former often has weeks before they can see one; the latter involves speedy trucks and/or flatbed tow vehicles. One Day, some six months after getting our M3 back in 2018, the SO got into the car, put it in reverse, and largest collection of error messages you ever saw lit up the screen. She called me, we dinged roadside assistance, and, in an hour or so, a guy with a tow truck showed up. When jumping the car didn't work he somehow got the car out of our garage, onto the flatbed, and off to Tesla, with the SO in the passenger's seat.

Long story short: It was the pyro fuse, likely due to a short in the pagoda wiring harness. The moral: Roadside assistance works faster when you've got a non-driveable car.

Good luck!

I was under the impression that the 12v battery ran all, all the time, with the HV battery keeping it topped. Your version makes much more sense! In your scenario, is the 12v battery there just to keep the car in sleep mode until it gets called to close the HV contacts?

If that's accurate, now I know why my Ohmmu has been throwing 12v errors lately: the car has been sitting more than normal while I recover from back surgery. It had not erred out in 7 months and has bitched 3 times in the last 30 days. As soon as I wake the car to do the Ohmmu BMS reset procedure (low voltage threshold is lower than a lead acid), the error clears and stays away for a week or so. Assuming what I'm thinking is accurate, you solved a riddle for me. Thanks!!