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Model 3 12v Battery issues, monitoring, Aftermarket replacement
- Thread starter hcdavis3
- Start date
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- 12 volt 12 volt battery
My testing several months ago seemed to indicate the car might simply wake up and top off the battery after X hours have passed. I had a 12V battery Smart Charger attached during my testing which stops charging when it see the car providing a charge voltage. With the charger attached the voltage never dropped below 12.8V which should have keep the car from needing to top off the battery; however, after some X hours the car woke up to top off the battery even though the voltage was above around 12.6V. A time based solution could work by checking the voltage when the car first wakes up (before starting the top off) and adjusting the time before the next wakeup to top off accordingly. IE.. the voltage was somewhat below 12.6V so need to wake up sooner next time. The 12.6V was about the voltage level when the car awoke to top off the battery without the Smart charger attacked. The 12.6V level might not be exact voltage but I hope you understand my logic.
I have just over 2 years on my original battery, thinking its probably smart to replace it soon but it just keeps on chugging.
I figured I'd see the message this winter that it needs replacement, and I still might. Luckily I live in the land of Tesla so I should be able to get a battery pretty easily.
I figured I'd see the message this winter that it needs replacement, and I still might. Luckily I live in the land of Tesla so I should be able to get a battery pretty easily.
I installed an Ohmmu Li Ion 12v in March. Did it myself because I like that stuff. Ohmmu is made outside of Phoenix. Comes with 4 year 100% warranty. Not prorated. Some users report over 5 years of service. Live in Tucson where 12v wet cells are dead in two years. Ohmmu is an outstanding company too deal with.
There's not one thing that points to a bad 12v battery. Some last less than 2 years, a few go for 7. If you smell eggs, that's one sign. If its bulge, that's another sign however hard to view under all the plastic. corrosion is a sign of a bad battery but again, hard to see under all the plastic.
JCtx
Member
I'd absolutely replace it if more than 3 years. I'm even thinking of replacing it at 2 
. But will continue to monitor this thread, in case Tesla changes (or changed) the charging logic. My guess is the battery is getting cooked by overcharging, but could be wrong.
. But will continue to monitor this thread, in case Tesla changes (or changed) the charging logic. My guess is the battery is getting cooked by overcharging, but could be wrong.My wives M3 just had a "12V battery need replacement" warning (or something like that). The car is 20 months old. Mobile Service came and replaced the battery under warranty but attributed the failure to my dash cam which is plug into 12v outlet. He said next time if I keep the cam and the battery fails, it is not covered by warranty. Have anyone heard that? I assume the cam is on when the car is on and the 12V battery is being charged. Another ploy to not provide warranty fix?
if you are plugged into the Tesla provided 12V outlet located under the center console lid, I can't imagine that hurting anything. Unless something has changed, the 12V power is only available when the PCS is operational which provides the power. When the car enters sleep mode no power is available to the center console outlet. The PCS can deliver somewhere around 200A, so the Dashcam power draw would be in the noise. Now if you are using a 12V outlet you or someone else installed that could be a different issue. If your Dashcam is drawing 12V power while the car is sleeping, you are adding at least slightly more charge/discharge cycles to the 12V battery. I you are using the center console outlet, I would remove the Dashcam before Tesla arrives to repair any car issue.
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I want to qualify my slightly more charge/discharge comment in my last post. It is my understanding the power draw on a typical Model 3 while sleeping is around 7W; therefore, if you had a dual DashCam setup that was using power during the car's sleep state, you could be pulling several watts. If that power draw is near 7W, you are potentially doubling the number of allowed lifetime charge/discharge cycles on the 12V battery. I am not familiar with power usage of the different Dashcams sold maybe someone more knowledgeable can weigh in? So this might be why Tesla makes the blanket statement to the Ranger/repair personnel , Dashcams are bad? Now the same thing could apply to ICE vehicles. Do ICE vehicle manufacturers have the same exception regarding their 12V battery warranty?
I know there are other threads about this 12V battery problem. But I got some good insights into this issue.
First my story.
Model 3 stealth performance is 8/2018 model - one of the first off the production line. Love the car.
About 4 days ago, I got the 12V battery issue warning. IMMEDIATELY i scheduled a service appt via the app
There were ZERO appointments within 2 weeks. So I scheduled it at the earliest time slot available. (This is the SF bay area so service department is likely busier than most locations)
I thought about calling tesla about this to get an earlier appointment but got busy with life. Also, I was curious how long the 12V battery would last after the warning and if Tesla has a good system to fix it.
Conclusion: 12 V battery lasted 4 days after warning. Thankfully died at home in my garage.
Tesla does not prioritize or recognize this 12V battery replacement as an urgent priority in terms of appointments (this can be fixed with just software)
My model 3 is about 2.5 years old and 36,000 miles.
I spoke with the towing guy who had to tow away my car to the service center after jumpstarting the car. Once the 12V battery dies, the doors cannot be opened from the outside, trunk cannot be opened, and even the charging port cannot be unhooked if you are plugged into charge.
Towing guy said, he's seen increasing model 3, 12V battery failures and rare cases of even 2020 models have this issue. Only seen one model Y with this issue (Which means little since so few model Y on the road currently).
So as soon as you see the warning, I would CALL tesla and demand a service appointment within 1-2 days MAX. 12V battery failure can be dangerous especially in the winter if you cannot even get back inside your car!!!
Anyone at Tesla seeing this. Tens of thousands of model 3 will need 12V battery replaced- let's not wait to have some angry tesla owner or someone's life put into danger.
As a tesla shareholder, I'm going to call the customer service make sure they are aware this is a HUGE service issue.
First my story.
Model 3 stealth performance is 8/2018 model - one of the first off the production line. Love the car.
About 4 days ago, I got the 12V battery issue warning. IMMEDIATELY i scheduled a service appt via the app
There were ZERO appointments within 2 weeks. So I scheduled it at the earliest time slot available. (This is the SF bay area so service department is likely busier than most locations)
I thought about calling tesla about this to get an earlier appointment but got busy with life. Also, I was curious how long the 12V battery would last after the warning and if Tesla has a good system to fix it.
Conclusion: 12 V battery lasted 4 days after warning. Thankfully died at home in my garage.
Tesla does not prioritize or recognize this 12V battery replacement as an urgent priority in terms of appointments (this can be fixed with just software)
My model 3 is about 2.5 years old and 36,000 miles.
I spoke with the towing guy who had to tow away my car to the service center after jumpstarting the car. Once the 12V battery dies, the doors cannot be opened from the outside, trunk cannot be opened, and even the charging port cannot be unhooked if you are plugged into charge.
Towing guy said, he's seen increasing model 3, 12V battery failures and rare cases of even 2020 models have this issue. Only seen one model Y with this issue (Which means little since so few model Y on the road currently).
So as soon as you see the warning, I would CALL tesla and demand a service appointment within 1-2 days MAX. 12V battery failure can be dangerous especially in the winter if you cannot even get back inside your car!!!
Anyone at Tesla seeing this. Tens of thousands of model 3 will need 12V battery replaced- let's not wait to have some angry tesla owner or someone's life put into danger.
As a tesla shareholder, I'm going to call the customer service make sure they are aware this is a HUGE service issue.
tstolze
Member
Not sure what the warranty is on the 12v battery, but I would think being under 3 years it would be covered.
A 51R should fit. About $100 at my Sam's Club, (pictured below). Probably a touch more at Walmart. I don't see why using one as a bridge unit, until Tesla got around to putting in one of their $85 batteries. Seems like cheap insurance to me, much preferable to getting stuck somewhere, and having to call for a tow.
Before doing the above, please read up how to do it, since it requires disconnecting the HV battery.
As for Cyberjoe's experience, I would consider a failing 12V a safety issue, that should get priority from Tesla. I can't see how it's less expensive for them to have to pay for towing, when a 12V fails on the road. Sometimes Tesla needs to be more proactive. It's like Elon's blindspot. Safety has to be priority #1. It's bad optics for the company not to take this more seriously.
Before doing the above, please read up how to do it, since it requires disconnecting the HV battery.
As for Cyberjoe's experience, I would consider a failing 12V a safety issue, that should get priority from Tesla. I can't see how it's less expensive for them to have to pay for towing, when a 12V fails on the road. Sometimes Tesla needs to be more proactive. It's like Elon's blindspot. Safety has to be priority #1. It's bad optics for the company not to take this more seriously.
DonTom
Member
I only have 5,427 miles on my 2018 Tesla M3, LW, AWD purchased new in Oct 2018. I have a few questions about the 12 volt battery. I still am using the original.
I recall there are a couple of wires below the right side of the left headlight (driver's side) under that round cap. I know those are to activate the doors and such if the 12 V batteries dies. I think I heard somewhere that all it takes is a little 9 volt battery to activate so the doors can be opened--and I assume drive with a dead 12 volt battery as then the DC2DC converter will supply the voltage from then on, while driving. I am surprised to hear the DC2DC converter is not activated also while charging.
Is it really possible to use a small 9V battery there? If so, I guess I should keep one in my pocket!
Another question is it worth it to install the Lithium 12 volt battery for $479.00?
And does the warning usually come on before the battery dies? I had no idea there was such a warning until I read this thread.
So when I am I mostly likely to need to replace this battery?
-Don- Reno, NV
I recall there are a couple of wires below the right side of the left headlight (driver's side) under that round cap. I know those are to activate the doors and such if the 12 V batteries dies. I think I heard somewhere that all it takes is a little 9 volt battery to activate so the doors can be opened--and I assume drive with a dead 12 volt battery as then the DC2DC converter will supply the voltage from then on, while driving. I am surprised to hear the DC2DC converter is not activated also while charging.
Is it really possible to use a small 9V battery there? If so, I guess I should keep one in my pocket!
Another question is it worth it to install the Lithium 12 volt battery for $479.00?
And does the warning usually come on before the battery dies? I had no idea there was such a warning until I read this thread.
So when I am I mostly likely to need to replace this battery?
-Don- Reno, NV
M3BlueGeorgia
Active Member
Yes, no, no, yes.
And when you get the warning, don't dally. Make an immediate appointment with Tesla through the application to get it replaced.
Brock-WI
Member
Is it true I can just buy a "spare" or replacement 12v battery from a tesla service center? I looked at the battery swapping procedure and can do that no problem. Our closest service center is 120 miles from here but we are occasionally near there and would like to just get one as a spare, especially if the replacement from Tesla is less than the $120 for the 51R from Walmart.
M3BlueGeorgia
Active Member
Its definitely something routinely done through Mobile Service, so being 120 miles from a Service Center shouldn't be a major concern.
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