Dead 12v Questions

[Commish]

About 5 days ago I had a bricked 3 because the 12v went dead. After about an hour, I returned to the car and it magically went back on. I did have the "Low 12v battery" message, so I made a service appointment, the first one being a week away. I did call the service center to come in, but I could not talk to a live person at all.

The car has bricked 2 more times since then and then suddenly turned on again after waiting it out (this was frustrating when I was in the middle of a forest at one point). Then, yesterday, I got a message from Tesla Service that there were no 12v batteries in stock and they needed to push my appointment out another week.

I knew my car wasn't going to make it that long, and sure enough, today my car is completely dead and after hours of sitting there will not turn on.

What are my options here? My 3 is my ONLY car and I need to get around. Correct me if I'm wrong, but I can't just grab any battery from the auto store to temporarily put in there. Everyone here has been downing the Ohmmu battery. Can I get a quick jump pack that connects to the 12v port in the Tesla?

It's Sunday officially so I can't talk to Service of course. Even if I could, it's not like they are going to give me a loaner car.

Seems to me my only option is to rent a car and pay for it myself. Is this correct? It's like a Tesla tax and that's BS.

 

[mattack4000]

Have you tried this?

MPP Lightweight Lithium Battery Kit | Mountain Pass Performance

 

[android04]

You can find a battery that will work at any auto parts store or big box store. The battery is Group Size 51R and is common in many Hondas. The only problem is that they are starting batteries designed to put out a lot of power to start an engine and then be charged up right away when the engine is running. Teslas need deep cycle batteries that are designed to be discharged more profoundly and then charged up. A starting battery will work, but will probably not last a long time (if you drive the car a lot it will probably last longer).

It's up to you whether it's worth the $150 for one of these starting batteries that may not last long so you can keep using the car. The OEM battery from Tesla costs $80 or free within warranty (when they have it in stock).

 

[Johnny Mac]

Love my ohmmu 12v battery!!!

 

[EnrgyNDpndnce]

You can definitely buy and install your own 12V at any auto parts store, I did so last month (also on a Sunday!). Just make sure you get an AGM battery. Can’t remember what AGM stands for but it’s specially designed for the heavy duty cycle Tesla demands. There are different sizes of AGM so best to take yours with you to make sure it’s the same size. @MTN Ranger has a good YouTube video on opening the frunk if your 12V is completely dead.

Oh, and don’t be surprised if the parts store isn’t helpful. I went to the O’Reilly in Mt Pleasant, SC and the guy there wanted to search his computer for me to find the exact match. So he was like, “What’s the make and model of your car?” And I said “Tesla Model 3.” And with a puzzled look he said “But what’s the make?” And I said “Tesla.” And again he said “yeah but what kind of car is it?” And I said “Tesla.” Then he said “but who makes it, like Ford or GM?” And I was like “Dude, it’s a Tesla.” Finally the guy working with him told him Tesla in fact is a manufacturer of cars and together they concluded Tesla was not in O’Reilly’s system. So I gave them my dead battery (removed and drove my wife’s car there) and they went to their stockroom and found an AGM of the same size.

 

[Margaritaboy]

Just swap out the battery yourself. You need a 10 mm socket and about 10 minutes to do it.

 

[Idkorcare]

Tesla really needs something that displays the 12v battery current voltage. I think when that warning pops up the car is assuming a fault with the battery and no longer charges it so if you keep driving it you will just run it down and brick it.

you could probably just charge the battery back up and do a hard reset to get it back to working till you can get the battery checked.you would want to charge it directly at the battery and slow charge it till the battery is prob at least 12.4 before turning on and resetting the Tesla.

 

[AxlxA]

Would you guys disconnect the HV battery before replacing? I see it in some but not other videos.

 

[lUtriaNt]

disconnecting the HV connector is not necessary when replacing the 12v.

Everyone here has been downing the Ohmmu battery

who is this "everyone"? I certainly did NOT down the ohmmu battery. have had it since april with no issues. let's not be dramatic.

 

[RayK]

disconnecting the HV connector is not necessary when replacing the 12v.

Everyone here has been downing the Ohmmu battery.

who is this "everyone"? I certainly did NOT down the ohmmu battery. have had it since april with no issues. let's not be dramatic.

However, according to the Ohmmu installation video on YouTube, they do recommend disconnecting the HV pack. My assumption is that it's for safety reasons and not critical to do so if you know what you're doing. I used to work on my CRT TVs all the time back in the '70s and '80s. I would always pull the power plug from the wall and discharge the high voltage section. Did I need to do that when I was just working on the tuner section? No, but it was safer that way. Your call.

 

[Commish]

who is this "everyone"? I certainly did NOT down the ohmmu battery. have had it since april with no issues. let's not be dramatic.

No intention of being offensive. It was a bad use of semantics. "A LARGE number of TMC forum participants" have been unenamoured by the alternative battery offerings on the market.

... is something I would have written if in a more cognitive state.

 

[Commish]

You can find a battery that will work at any auto parts store or big box store. The battery is Group Size 51R and is common in many Hondas. It's up to you whether it's worth the $150 for one of these starting batteries that may not last long so you can keep using the car. The OEM battery from Tesla costs $80 or free within warranty (when they have it in stock).

This was very helpful, thanks. Right now I have the option of renting a car for a week at $150/day or putting in this battery... so battery wins.

You can definitely buy and install your own 12V at any auto parts store, I did so last month (also on a Sunday!). Just make sure you get an AGM battery.

Thank you! Again, very helpful... and a funny story!

 

[xcat]

I spoke w a Tesla mobile ranger on the need of disconnecting the high voltage battery prior to the 12 V. The book calls for it to be disconnected aside from safety by disconnecting will clear the service 12 V battery soon message.

 

[android04]

I spoke w a Tesla mobile ranger on the need of disconnecting the high voltage battery prior to the 12 V. The book calls for it to be disconnected aside from safety by disconnecting will clear the service 12 V battery soon message.

All you have to do is disconnect a harness under the rear seat to disable the 12v output from the DC-DC converter since if you short the positive battery cable to ground you will cause some sparks. See here for details on the harness under the rear seat Tesla Model 3 Hard Reset | Mountain Pass Performance

 

[fseir]

I swear reading this thread jinxed me, lol!

Walked into my garage last night and noticed a strong smell of sulfur. Thought it was some butane camping stove canisters leaking, so I moved them outside, but the odor didn’t clear, and after a little while, figured out it was coming from the car.

Tried to open the driver door, and it was dead, but oddly, the window was down slightly and the mirror was folded out. The rear driver’s side door was also unresponsive, so I started worrying about how I was going to get into the car. Fortunately, the passenger door opened, but the window actuation was slow, and it was acting like it had very low power. The foot well ambient light on the passenger side was flickering like a horror movie, but the light on the driver’s foot well was off completely. No other signs of life in the car.

Since the driver’s window was down a little, I was able to use the emergency handle to open the driver’s door without damaging the window.

Next, I tried to remove the charging cable, but there was no power, so I couldn’t. I tried to open the trunk, but it wouldn’t open. I could hear slight sounds of electrical motor actuation when I pressed the trunk lid button, so I kept trying, and eventually, the lid opened and I was able to pull the charging cable release cord. Interestingly, the passenger side light in the trunk was also flickering on and off, but the driver’s side light was totally off. It was like the passenger side of the car had some power, but the driver side had none.

I contacted roadside assistance and they sent a flatbed truck out (a contracted towing company). First they tried hooking up a battery to the 12V, but it did absolutely nothing. If anything, it seemed to kill it completely, as the right sided flickering stopped and all electrical motor sounds ceased. Then the guy started trying to figure out how to get the car onto dollies, and it was obvious he didn’t really know what he was doing, and he wasn’t being very careful. Since it was getting late, and I didn’t want him to damage the car, I told him to just leave it, and I would contact Tesla and try to get mobile service out as soon as possible.

So now that it’s the weekend, I have to wait until Monday to call, and hopefully they can send someone out to swap out the battery. And I really hope the weird 1/2 of the car not having any power, doesn’t mean anything more ominous about the electrical system. Haven’t heard anyone report that before.

I’ll post an update if it turns out to be more complicated than a battery swap.

 

[iwannam3]

You can definitely buy and install your own 12V at any auto parts store, I did so last month (also on a Sunday!). Just make sure you get an AGM battery. Can’t remember what AGM stands for but it’s specially designed for the heavy duty cycle Tesla demands..

AGM = Absorbed Glass Mat the acid is not free to slosh around, it is absorbed on a mat of fiberglass fibers and held close to the lead plates. They don't release hydrogen gas like regular battery does. They are sealed with no caps on top to add water too. They are required when in living spaces like inside an RV or in the trunk of my Mini Cooper and Prius and other cars. They usually have a little vent hose to vent in case of overcharging.

 

[android04]

I swear reading this thread jinxed me, lol!

Walked into my garage last night and noticed a strong smell of sulfur. Thought it was some butane camping stove canisters leaking, so I moved them outside, but the odor didn’t clear, and after a little while, figured out it was coming from the car.

Tried to open the driver door, and it was dead, but oddly, the window was down slightly and the mirror was folded out. The rear driver’s side door was also unresponsive, so I started worrying about how I was going to get into the car. Fortunately, the passenger door opened, but the window actuation was slow, and it was acting like it had very low power. The foot well ambient light on the passenger side was flickering like a horror movie, but the light on the driver’s foot well was off completely. No other signs of life in the car.

Since the driver’s window was down a little, I was able to use the emergency handle to open the driver’s door without damaging the window.

Next, I tried to remove the charging cable, but there was no power, so I couldn’t. I tried to open the trunk, but it wouldn’t open. I could hear slight sounds of electrical motor actuation when I pressed the trunk lid button, so I kept trying, and eventually, the lid opened and I was able to pull the charging cable release cord. Interestingly, the passenger side light in the trunk was also flickering on and off, but the driver’s side light was totally off. It was like the passenger side of the car had some power, but the driver side had none.

I contacted roadside assistance and they sent a flatbed truck out (a contracted towing company). First they tried hooking up a battery to the 12V, but it did absolutely nothing. If anything, it seemed to kill it completely, as the right sided flickering stopped and all electrical motor sounds ceased. Then the guy started trying to figure out how to get the car onto dollies, and it was obvious he didn’t really know what he was doing, and he wasn’t being very careful. Since it was getting late, and I didn’t want him to damage the car, I told him to just leave it, and I would contact Tesla and try to get mobile service out as soon as possible.

So now that it’s the weekend, I have to wait until Monday to call, and hopefully they can send someone out to swap out the battery. And I really hope the weird 1/2 of the car not having any power, doesn’t mean anything more ominous about the electrical system. Haven’t heard anyone report that before.

I’ll post an update if it turns out to be more complicated than a battery swap.

The lights and power flickering one one side and completely off on the other are nothing to worry about. Most likely it's due to VCLEFT and VCRIGHT having slightly different thresholds for what voltage is enough to power them. VCLEFT and VCRIGHT are the vehicle controllers that power and control things in the car. One is on the left side of the car beside the driver's dead pedal, and the other is on the opposite side where the passenger's feet are. They receive power from VCFRONT located on the firewall under the frunk. Since the 12v battery is low, they are right on the edge of having enough power or not to work correctly. Yours have slightly different thresholds (or slightly different power wire lengths) that affect how much voltage gets to them and that would explain the difference.

 

[fseir]

The lights and power flickering one one side and completely off on the other are nothing to worry about. Most likely it's due to VCLEFT and VCRIGHT having slightly different thresholds for what voltage is enough to power them. VCLEFT and VCRIGHT are the vehicle controllers that power and control things in the car. One is on the left side of the car beside the driver's dead pedal, and the other is on the opposite side where the passenger's feet are. They receive power from VCFRONT located on the firewall under the frunk. Since the 12v battery is low, they are right on the edge of having enough power or not to work correctly. Yours have slightly different thresholds (or slightly different power wire lengths) that affect how much voltage gets to them and that would explain the difference.

Awesome, that’s very reassuring. Thanks!

And it was lucky that I was able to still open the passenger door and trunk because of this variation in voltage threshold.

 

[fseir]

Guess another question, is why all of these 12V batteries are failing so soon? The 12V in my leaf lasted 6 years.

I was lucky that my model 3 bricked inside of my garage, especially since two of the windows are part way down and can’t be raised.

 

[dmd2005]

Have you tried this?

MPP Lightweight Lithium Battery Kit | Mountain Pass Performance

I’ve had the MPP Lightweight battery for the last year after getting a Tesla 12V battery replaced under warranty after 9 months of ownership. I didn’t want to get stranded with a dead 12V and I got the MPP kit that is used in small planes.