Model 3 12v Battery issues, monitoring, Aftermarket replacement

[rrolsbe]

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.

The following comments are correct AFAIK. Since you have low mileage on your 2+ year old car, the 12V battery has probably seen many more charge cycles than the norm; therefore, there is a chance it might be nearing the end of it's useful life.

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.

The wires behind the tow hook cover only open the frunk to give access to the 12V battery area. Tesla made a firmware change several months back that disallows opening the frunk,, via the tow hook wires, when the 12V battery is functional.

Anytime the car is awake the DC-to-DC converter is operational. In fact, you can disconnect the 12V negative cable anytime the car is in the awake state and everything works fine (you will get a message on screen that the 12V battery is disconnected). The 12V battery is required to close the HV contactors to transition from the sleep to operational awake state.

Is it really possible to use a small 9V battery there? If so, I guess I should keep one in my pocket!

Yes, last time i tried it. Maybe someone else who has tried it recently can confirm?

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

 

[rrolsbe]

Its definitely something routinely done through Mobile Service, so being 120 miles from a Service Center shouldn't be a major concern.

Your absolutely correct about the Rangers replacing the 12V batteries. Since the cost is about the same, I might purchase a spare AGM battery from Tesla in lieu of a Jumpstarter battery. I would keep this battery in the frunk along with a 10MM wrench to allow change out and a 9V battery in my pocket. If I am stranded due to a 12V battery failure, I would much rather install the spare battery and get on down the road in 10 minutes. I can deal with Tesla regarding the failed battery later. If Tesla declined to cover the failed 12V battery under warranty so be it. Even though the 12V battery should be warranted for 4 years or 50K miles, the hassle factor of waiting for roadside assistance would probably not be worth it (unless I am parked in my garage and do not need to go anywhere). When I go hiking in the mountains I almost never have Cellphone service, so calling for Roadside service would be a problem; likewise, even if road side assistance would come to a mountain trailhead, how long might that take.

 

[Brock-WI]

Your absolutely correct about the Rangers replacing the 12V batteries. Since the cost is about the same, I might purchase a spare AGM battery from Tesla in lieu of a Jumpstarter battery. I would keep this battery in the frunk along with a 10MM wrench to allow change out and a 9V battery in my pocket. If I am stranded due to a 12V battery failure, I would much rather install the spare battery and get on down the road in 10 minutes. I can deal with Tesla regarding the failed battery later. If Tesla declined to cover the failed 12V battery under warranty so be it. Even though the 12V battery should be warranted for 4 years or 50K miles, the hassle factor of waiting for roadside assistance would probably not be worth it (unless I am parked in my garage and do not need to go anywhere). When I go hiking in the mountains I almost never have Cellphone service, so calling for Roadside service would be a problem; likewise, even if road side assistance would come to a mountain trailhead, how long might that take.

My thoughts exactly. I can change it myself easily enough and if it happened during a snowstorm while out shopping, that wouldn't be fun. Also waiting on the time for a ranger to come and replace even if the car happened to be at home seems silly. I wouldn't want them to waste 5 hours of their day when they could be helping someone who needs something now when I can change it myself.

Heck I might just get one and swap it right away for piece of mind. Now to see if I can just pick one up of if I have to order it or?

 

[DonTom]

And when you get the warning, don't dally. Make an immediate appointment with Tesla through the application to get it replaced.

I plan on replacing it myself. A lot less hassle. I usually fix my own problems even during the warranty period at my own cost, when possible.

Replacing the 12 volt battery is a very simple job:

 

[DonTom]

Mine is also a Oct 2018 build. I carry a 9volt battery in all my coats. I don't think it opens the doors, but opens the frunk, so you can access the 12V. When will you need a new battery? Of course when you least expect it.

In that case, I will carry the 9V battery AND keep a new spare 12V battery in the Frunk. Just for the fact that the lithium should have a very long shelf life and is lighter and can be stored in any position, that makes it good idea to keep in the frunk if I do not want to replace it before the stock battery craps out.

-Don- Reno

 

[KenC]

In that case, I will carry the 9V battery AND keep a new spare 12V battery in the Frunk. Just for the fact that the lithium should have a very long shelf life and is lighter and can be stored in any position, that makes it good idea to keep in the frunk if I do not want to replace it before the stock battery craps out.
-Don- Reno

Sounds like a plan. I keep a Noco lithium starter in the frunk. The car doesn't need much from the 12V, so I hope the Noco will have just enough power to get the car going, if the 12V fails somewhere. Then I can run over to Sams or Walmart to get a 51R to replace it, after checking with Tesla and finding out how long it will take to get a warranty replacement via mobile ranger.

 

[DonTom]

Sounds like a plan. I keep a Noco lithium starter in the frunk. The car doesn't need much from the 12V, so I hope the Noco will have just enough power to get the car going, if the 12V fails somewhere. Then I can run over to Sams or Walmart to get a 51R to replace it, after checking with Tesla and finding out how long it will take to get a warranty replacement via mobile ranger.

Is the 12V required to drive the car if you can get in it?

-Don- Reno, NV

 

[cyberjoe]

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

the warning came and the car lasted only about 4-5 days. But I would literally get on it within 48hrs TOPS. The car is like a dead brick when the battery goes. you cannot even open the door!

This is why I'm worried as a tesla investor EVEN more than as a driver. Huge safety issue and PR issue. Thousands of people will start having this issue in the coming months as 2019 model 3 will start getting dead batteries - how many were sold in 2019 - A TON of model 3s!

 

[cyberjoe]

Is the 12V required to drive the car if you can get in it?

-Don- Reno, NV

The car is completely DEAD. you cannot get inside the car, you cannot open the door or trunk. Could be dangerous situation in the winter and if babies/toddlers inside the car when the car battery dies.

 

[DonTom]

The car is completely DEAD. you cannot get inside the car, you cannot open the door or trunk. Could be dangerous situation in the winter and if babies/toddlers inside the car when the car battery dies.

I realize we cannot get in the car as the locks are 12 volts. But I was wondering what would happen if we could. Seems to me if we can get the car on, the DC2DC converter will supply the 12 volts. But is the 12V also required to get the car turned on?

-Don- Reno

 

[rrolsbe]

If the 12V is dead, you use the 9V battery to open the frunk. Then remove the cable from the negative 12V battery terminal using a 10MM wrench. Then either swap in your good spare battery or connect your jumpstarter between the positive post and the removed negative cable. You could connect the jumpstarter without removing the negative side but if the failed battery has developed a short you would have a problem. When power is connected to the battery cables, the HV contactors will close allowing you access to the car and it can then be driven. The 12V battery is only needed to close the contactors and run the 12V accessories while the car is in the sleep state. I recommend watching the battery swap out video someone listed above. You would not need to lift the connector under the back seat because the contactors would already be open due to the failed 12V battery. Also, if you do not understand what/why you are doing the steps outline above, contact Tesla Roadside service.

 

[JCtx]

I heard somewhere that all it takes is a little 9 volt battery

I didn't know that, so learned something important today. However, I saw under my car, and there's nothing. The only round part is the one for the tow hook... but I couldn't remove it. Can somebody please post a picture of the '9-V' battery cover? And how to remove it, exactly? Thank you.

I plan on replacing it myself. A lot less hassle. I usually fix my own problems even during the warranty period at my own cost

Me too, and will probably replace the battery pro-actively with a Tesla one (since it's the cheapest). Having said that, your linked video doesn't mention anything about removing the connector under the rear right seat. It'd be dangerous to remove the battery as shown on that video if it has even a little current, so I'd always remove the seat connector before removing the + post. I need to re-check the procedure, but I remember it was remove '-' cable, remove rear seat connector, then remove '+' battery terminal, and replace battery.

If the 12V is dead, you use the 9V battery to open the frunk. Then remove the cable from the negative 12V battery terminal using a 10MM wrench. Then either swap in your good spare battery or connect your jumpstarter between the positive post and the removed negative cable.

Thank you for that important information. So I guess it's important to also have one of those Li-Ion small jump-starter battery packs, to re-start the car, and get to your destination. The only thing we'd have to put somewhere is a '9V' battery. I'll take care of doing all of that soon, but need to learn where exactly is the 9V plug, and how it's removed. Thank you.

EDIT: Looked at a video on Youtube, and the wires are behind the tow-hook plug. I had a hard time removing it for the first time, but could do it without damage. The hook is at the 1:30pm position (where you need to push), and the clip at the 7:30pm position, which is where you need to stick a plastic trim tool to pop out the cover. In my car, the '-' wire was attached to the cover, rather than the '+', but checked voltage after waking up the car, and there's no voltage, so no risk of a short. Will try to fit a 9V battery in the hole there (with terminals taped up), and see if I can close the cover; it'd be the perfect solution. By the way, read that if the car is locked, you CANNOT open the frunk like that, so that'd be a problem if true.

 

[rrolsbe]

I didn't know that, so learned something important today. However, I saw under my car, and there's nothing. The only round part is the one for the tow hook... but I couldn't remove it. Can somebody please post a picture of the '9-V' battery cover? And how to remove it, exactly? Thank you.


Me too, and will probably replace the battery pro-actively with a Tesla one (since it's the cheapest). Having said that, your linked video doesn't mention anything about removing the connector under the rear right seat. It'd be dangerous to remove the battery as shown on that video if it has even a little current, so I'd always remove the seat connector before removing the + post. I need to re-check the procedure, but I remember it was remove '-' cable, remove rear seat connector, then remove '+' battery terminal, and replace battery.


Thank you for that important information. So I guess it's important to also have one of those Li-Ion small jump-starter battery packs, to re-start the car, and get to your destination. The only thing we'd have to put somewhere is a '9V' battery. I'll take care of doing all of that soon, but need to learn where exactly is the 9V plug, and how it's removed. Thank you.

It is not a 9V plug it is two wires located behind the front tow hook cover. The car users manual shows using a 12V battery but user have found out a brand new 9V battery works.

The are several videos on Youtube showing how to open the frunk using a 9 volt battery, I recommend watching some of them. The tow hook cover can be hard to remove as can retrieving the wires. Watch the video(s) and try it for yourself before you are in a pinch.

 

[DonTom]

I didn't know that, so learned something important today. However, I saw under my car, and there's nothing. The only round part is the one for the tow hook... but I couldn't remove it. Can somebody please post a picture of the '9-V' battery cover? And how to remove it, exactly? Thank you.

It's the front of the car, not under:

 

[DonTom]

That was the first time I removed that cap. I am glad I did, because I cannot figure how to use it. There is only a single wire. How is that going to work? What do we used for the return path or ground with our 9 V battery?

Edit: Disregard. See posts below.

-Don- Reno, NV

 

[DonTom]

 

[DonTom]

I didn't quite understand that. What do we do it the 12 volt battery is 100% dead and we cannot use the phone to unlock it????? And if we can unlock the doors, why do we need to use the 9 volt battery to unlock the Frunk?

EDIT:I just now watched it again. I now see the 9V will work when the 12 battery is dead, but not now work when the 12 Volt battery is good (unless the car is unlocked anyway).

Also, I couldn't find the positive wire in my hole. I will look again now that I know that it should be in there somewhere.

Edit: I Just found the positive wire, it Ys with the wire on the cap 4.5 inches from the wire on the cap. It was stuck in there very tight.

I had no trouble removing the cap with a straight slot screwdriver from around 7 or 8 o'clock on the cap.


-Don- Reno, NV

 

[DonTom]

I just now used my FOB to unlock my Tesla M3 and used the 9V battery to open the Frunk. Worked perfectly. So then I locked the doors with my FOB and tried the 9V battery again and it did NOT work, just as as it shouldn't,

I guess the only way we can do a real test is either wait for the 12V battery to go dead or disconnect (using the correct procedure to to turn off the car--Safety & Security--Power Off). I will just assume it will really work when the 12 V battery really goes dead, regardless if the car is locked or not.

BTW, I just discovered turning the car "off" does NOT disable the 12VDC. I could still use the auto windows and FOB with the car turned off. But only the brake pedal turns the screen and car back on.

IMO, everybody who owns a Tesla M3 should try a 9V battery to open the Frunk to be sure they can when the battery really goes dead. Car has to be unlocked (unless your 12V Battery is dead!).

-Don- Reno, NV

 

[JCtx]

Okay gang, went to the garage and popped the plug; it was a PITA the first time. I did it THREE times, to loosen the plastic a little bit, and now I can open it without any tools, which is the goal. In addition, I wanted a solution to the 9V battery issue, and this is what I did (pics below): I shoved a brand new battery (with the posts double-taped) in there, positioned so I can push on the 1:30pm position, cut off the part of the cover plug where one wire was attached (which is not needed IMO. Plus if somebody is going to steal it, prefer the thief to take it easily, rather than pull on those wires), and taped the 2 wires together, separated with tape, although there's no voltage on them. Now, I don't need to remember carrying a 9V battery . And it's good to know we can open the frunk with it even if car is locked with a dead battery.

Finally, to 'start' the car, we still need a 'jumper' battery, correct? So will buy one of those light portable packs I have on my ICE car ($100), and a 10mm wrench, and permanently leave them in the frunk, to be able to drive off if the 12V battery craps out.

 

[JCtx]

Hey gang, the edit time elapsed, so need to start a new post. My wife asked how exactly to 'start' the car, and I didn't have an answer. By the way, I added a yellow zip-tie to the cables, to fish them out easily, in case they hide, since I removed the part where one of them plug to the cap. Super easy to open now, and I have the battery there, so no worries anymore.

After you open the frunk, I have the following questions:
1. It should be 99.99% safe to just jump the battery like an ICE car, without the need to remove negative cable, no? But is it best to attach negative to the battery itself, or to a chassis ground, like on an ICE car? And yes, always attach positive terminal first, then negative (either to ground, like on ICE cars, or battery terminal, depending what the experts say). Or is the negative terminal absolutely has to be removed, and attach the jumper terminal there? Then turn on battery pack as a jumper.
2. After car is energized, and you open the door, what's next? Can you remove the jumper pack at that point? Or do you need to actually put the car in D, before removing jumper device? Please provide details. Thank you .