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12V Battery Failure Experience

Jdcorbitt3

Member
Feb 10, 2016
222
201
Ocala, FL
What convinces you it's a software related issue?
My experience with about 10 other Teslas. Prior to this, All the Teslas have given us a warning that the battery was failing. The two of us, after doing a software update, have the same failure, with no warning. Then I jumped my battery, and left the driver’s door open for about an hour. This kept the DC to DC convert running to charge the 12V battery. Later that day I drove it around the community. The “replace battery soon” message displayed until they replaced the battery.
Therefore, the “replace battery soon” message functions properly. I have to conclude that my battery drain was overnight where the car was not awaken. The neighbor went several days without driving. He did not know how to jump start his to get it online again.
I am sure more data points will be showing up soon enough.
 

SWFlaM3

Member
Apr 21, 2020
24
15
Florida
I only recently picked up my M3 so I don’t know much about It yet. This forum helps me learn more. Why can’t I replace the 12v battery myself? Are there any instructions anywhere?
 

XLR82XS

D M C
Jul 26, 2019
3,126
1,762
SWFL | Vegas
I only recently picked up my M3 so I don’t know much about It yet. This forum helps me learn more. Why can’t I replace the 12v battery myself? Are there any instructions anywhere?
You can. Disconnect terminals, remove battery, install new battery. Instructions really not needed for anyone with any car aptitude.
 

vickh

Active Member
Dec 16, 2018
3,106
485
az
You can. Disconnect terminals, remove battery, install new battery. Instructions really not needed for anyone with any car aptitude.

It's easier to access than the S, but still not as easy as other ICE cars

We should have a battery gauge on the display. Wonder if they can do it as a software OTA ? There are aftermarket gauges in the interim
 

vickh

Active Member
Dec 16, 2018
3,106
485
az
My experience with about 10 other Teslas. Prior to this, All the Teslas have given us a warning that the battery was failing. The two of us, after doing a software update, have the same failure, with no warning. Then I jumped my battery, and left the driver’s door open for about an hour. This kept the DC to DC convert running to charge the 12V battery. Later that day I drove it around the community. The “replace battery soon” message displayed until they replaced the battery.
Therefore, the “replace battery soon” message functions properly. I have to conclude that my battery drain was overnight where the car was not awaken. The neighbor went several days without driving. He did not know how to jump start his to get it online again.
I am sure more data points will be showing up soon enough.

This convinces me to drive the car at least once a week.
 

lUtriaNt

Member
Mar 16, 2020
624
551
Los Angeles
https://34c9c8a1-7edd-4e5b-8d85-78f...a10dd8bd324d1bb3b0537bf065ea86.pdf?index=true

these (upgraded for the model 3) instructions state you have to disconnect the HV cables under the rear seat. a bit different story than this jan 2019 produced video....

EDIT: reached out to this company to inquire and they state doing this additional procedure is mainly for the DC DC circuitry to properly "re learn" the new battery. a small percentage of cars were showing a "check 12v battery" alert and doing this procedure would rectify that. i asked why it was not included in the 2019 video and they simply stated they learned about this over time and that is why the updated install procedures were added. they also said if you did not have the alert you may not need to do this step.

After all that, the install is at least easy, but ill need to give this more thought. love the benefits gained.. tough call..
 
Last edited:

SWFlaM3

Member
Apr 21, 2020
24
15
Florida
Here’s a thought. How about if you connected a 12v source to the vehicle’s cables before disconnecting the 12v battery cables. Then, disconnect the battery, replace it, reconnect the vehicle cables to the new battery. Finally remove the temporary 12v source. That way the vehicle never looses it’s 12v source. Thoughts?
 

Jdcorbitt3

Member
Feb 10, 2016
222
201
Ocala, FL
I drove my car the night before the failure. When I powered it up, the car wanted to do another software update after the battery was replaced. I suspect Tesla pushed a mandatory update, as the car did not ask for my permission to do that update. My car has been fine since. I have gone 24 hours without it plugged in, as well as plugged in. Both cases, when powered up it was fine.
 

TMThree

Active Member
Mar 28, 2019
1,116
1,611
USA
Yeah I saw that, not sure how long they last in storage. My 3 is only 8 mo.s old.

mine is 13 months. I'm not going to replace the factory battery till its at least 2 years old, but at this point, no reason to replace it while we're all under house arrest with cv19.
 

vickh

Active Member
Dec 16, 2018
3,106
485
az
mine is 13 months. I'm not going to replace the factory battery till its at least 2 years old, but at this point, no reason to replace it while we're all under house arrest with cv19.
Yeah, but I wanted to take advantage of the covid deal at ohm. Only if they last in storage though?

Also batteries don't last in our AZ heat to warranty standards. I would get them replaced routinely under warranty. I wonder if Tesla 12 V will be the same

This reminds me I have to figure out Sears Diehard warranty now that we only have franchise homestores here.
 

TMThree

Active Member
Mar 28, 2019
1,116
1,611
USA
for some of us, its a regular day and we gotta head in to the office. ;)

I get to work from home. It's like a dream come true. I could have always worked from home, but the company prefers we go into the office. I'm loving it. My house is like a resort. I was on a conference call this afternoon from the pool.

On the flip side, company is losing business. Shortfall of about 100 million and they plan to take it out of contractors and cutting projects. So this is about to get ugly, real fast.
 

luke68bird

Member
Mar 22, 2019
203
114
Houston TX
My 2018 August build has been acting up over the past few weeks with a service apointntment in a week. Tesla does not provide a human to talk to or answer any of my text questions but I'm fairly certain the 12V is failing. Car is at 27k miles in Houston TX heat. This thread convinced me to advise the boss lady that she might get stranded. I'm on repair number 8 for a car less than 2 years old.
 

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