12 volt may or may not die before I can get it replaced🤷‍♂️

[Mesogreat]

Woke up to the screen saying my 12v is dying. Hell of a coincidence this happened the day I got fsd. Now it’s looking like I can’t get a mobile appointment until Thursday. Do we think my battery going to die before my appointment . If so what’s the procedure after my car turns in to a giant paper weight. The tesla service center has been pretty cold and heartless about the whole thing. I’m kind of freaking out as my car is needed for my work. Lives are actually involved with the sudden disappearance of a vehicle. I’m just trying to work out the what if’s.

 

[brkaus]

Drive to the Tesla service center and see if they can replace it in the spot. If not, purchase battery and DIY.

If none of above, report back and let us know if you make it a week.

I suspect they have made software changes to make detection better and possibly keep the DC2DC on once a bad 12v is identified.

 

[InDaClub]

Woke up to the screen saying my 12v is dying. Hell of a coincidence this happened the day I got fsd. Now it’s looking like I can’t get a mobile appointment until Thursday. Do we think my battery going to die before my appointment . If so what’s the procedure after my car turns in to a giant paper weight. The tesla service center has been pretty cold and heartless about the whole thing. I’m kind of freaking out as my car is needed for my work. Lives are actually involved with the sudden disappearance of a vehicle. I’m just trying to work out the what if’s.

When my 12v battery failed, I contacted Tesla Roadside and they came to my house and swapped out the battery in about 15 mins. Excellent service with no fuss.

 

[jjrandorin]

My own single hearsay sample is that of a pretty early S owner

So, now can we say the sample size on the other side of the ledger is one, not zero?

No, we cant, because your 1 example is from a model S and this is the model 3 subforum where we are talking about model 3s.

You can search this subforum for more threads about 12v dying with or without warning, there are more than a couple.

 

[AlanSubie4Life]

I suspect they have made software changes to make detection better and possibly keep the DC2DC on once a bad 12v is identified.

I can confirm they have as of beginning of 2022. Was a non issue. Car tells you it is keeping the DC-DC on (not in those words though).

 

[RoBoRaT]

I can confirm they have as of beginning of 2022. Was a non issue. Car tells you it is keeping the DC-DC on (not in those words though).

From the service manual - electrical precaution regarding 12V battery says this and more:

CAUTION
The HV battery in Model 3 will support a damaged/over discharged 12V battery whether or not the vehicle is being driven. However, upon detection of 12V battery degradation, the vehicle provides alerts indicating that the 12V battery needs replacement. If these alerts are ignored for a considerable period of time, the HV battery can become discharged to the point of no longer supporting the 12V battery (and the vehicle will have to be jump-started), or the 12V battery may become overheated due to nearly continuous charging.

CAUTION
Over discharging a 12V battery can cause permanent damage to the battery and increase the likelihood of overheating during charging. If a vehicle has an over discharged or "dead" 12V battery, always replace the 12V battery. Even if an over discharged battery is charged again successfully, the damage incurred is likely to cause future reliability problems.

CAUTION
Prevent unnecessary 12V battery replacement. If a vehicle is unable to support the 12V battery, or has a low HV State of Charge and is unable to be recharged, disconnect 12V power (refer to Service Manual procedure 17010200). Keeping the 12V battery connected might result in damaging the 12V battery through over -discharge.

 

[AlanSubie4Life]

From the service manual - electrical precaution regarding 12V battery says this and more:

CAUTION
The HV battery in Model 3 will support a damaged/over discharged 12V battery whether or not the vehicle is being driven. However, upon detection of 12V battery degradation, the vehicle provides alerts indicating that the 12V battery needs replacement. If these alerts are ignored for a considerable period of time, the HV battery can become discharged to the point of no longer supporting the 12V battery (and the vehicle will have to be jump-started), or the 12V battery may become overheated due to nearly continuous charging.

CAUTION
Over discharging a 12V battery can cause permanent damage to the battery and increase the likelihood of overheating during charging. If a vehicle has an over discharged or "dead" 12V battery, always replace the 12V battery. Even if an over discharged battery is charged again successfully, the damage incurred is likely to cause future reliability problems.

CAUTION
Prevent unnecessary 12V battery replacement. If a vehicle is unable to support the 12V battery, or has a low HV State of Charge and is unable to be recharged, disconnect 12V power (refer to Service Manual procedure 17010200). Keeping the 12V battery connected might result in damaging the 12V battery through over -discharge.

Yep, that all makes sense, and demonstrates that Tesla is indeed handling this. Sounds like nothing to worry about - as long as the failure mode is detected.

A sudden catastrophic internal short of a 12V may occur too fast to be detected, so I would expect some failures to still not be handled. Depends how good their software is; probably in most cases it is recoverable before it becomes unrecoverable.

Just be sure to plug in that Tesla if your 12V has failed (and has been detected), and should be good, according to the manual.

 

[roblab]

I always figured you could go to any gas station and get a new 12-volt battery. No?? This battery does not have to have deep charge or high cranking amps, it simply has to be recharged by the main battery when it gets low enough to need it to operate the wipers, radio, etc. I don't plan to spend extra money on a Lithium battery when I don't need it.

 

[KenC]

So, after all these discussions of changing one's 12v battery, I finally gave up waiting for a car warning, and swapped mine out after 50months.

Took less than 15mins. Not really all that different than a regular 12v swap, other than you have to take a few more precautions, like leaving a window down or your door open, disconnecting the HV battery and doing a shutdown. An experienced battery tech probably could do it in 5mins.

Anyway, I did a battery test on my old battery just to see how it was doing:

So, it only scored a 62% SoH, and resistance was up 5.74mOhms. I guess it was good to change it out now, rather than having to do it in the middle of a winter storm.

 

[3sr+buyer]

I always figured you could go to any gas station and get a new 12-volt battery. No??

It needs to be the group 51R size.

Also, there is a vent hose attached to the OEM battery. Not all group 51R batteries have a vent that matches the vent hose.

 

[ucmndd]

I always figured you could go to any gas station and get a new 12-volt battery. No??

What gas stations do you go to that have a broad selection of 12v lead acid batteries?

The gas stations in your area carry 20x more varieties of cheese than they do 12 volt batteries.