Model 3 12v Battery issues, monitoring, Aftermarket replacement

[DubP]

Okay, went to the Hankook battery site, and EFB is Enhanced Flooded Battery, which gives 3x the life of regular MF, Maintenance Free, batteries.

View attachment 655468
The Atlas battery is the one I underlined. Note, it's a MF, maintenance free, not an AGM. Also, note the that the 3 batteries marked as "for Tesla", two are MF, and one is AGM, so it's not unique nomenclature for the Tesla battery. A MF is not an AGM.

Thanks for the correction. I just assumed the original Atlas battery was AGM because I couldn't hear any liquid sloshing. Maybe it was empty lol.

 

[Kevy Baby]

Anyone looking into replacement 12V should also check out this thread: Model 3 12v Battery issues, monitoring, Aftermarket replacement

The second post has links to several threads on the topic (including to this thread) - thanks to @jjrandorin for compiling that list.

 

[Mrcarcrazy]

Just got the 12v battery warning so I scheduled with mobile service as it should still be under warranty (22months, 30k miles). They are coming to my work on Monday.

 

[danelle1126]

I just experienced my 3rd power failure within a year for my M3LR purchased in 2018. Not sure which of the below options to choose. Please advise:

1) Let Tesla handle everything. It failed at my home (won't start, doors won't open) this time, so I would need to tow it to dealership. Earliest available appointment was May 13 with no mobile option.

2) Attempt to jump start by popping trunk with 9-volt and buying portable jump starter, then hopefully drive it to dealership May 13. Better logistics-wise if it works.

3) Try to replace battery myself. Worried that this may void warranty if I make a mistake or risk potentially declaring car a lemon (or, get myself electrocuted). Plus, sounds like I should go to Tesla dealership anyway to get their particular battery for replacement.

FYI, before the first failure, the 12 volt battery warning came on around April/May 2020 and a Mobile Tech came out and did something to temporarily remedy the issue. Then the first power failure occurred in June 2020 when I just finished supercharging and was attempting to drive away. Tesla installed a brand new 12 volt battery in September 2020 after the 2nd failure. The 3rd failure occurred Friday after I had supercharged the last time that I drove it. I am wondering if there is a correlation with supercharging since I only do that every few months. Anyway, I've just about lost faith that Tesla can fix this issue.

 

[KenC]

I think choice 1. Hope they can ID the actual problem.

 

[DonTom]

Even though I had no issues with my 12V battery, I just replaced it a few minutes ago with a new lithium 12 Volt battery and did a lot of testing, because I was curious about things. There must have been a recent update that changed a lot of things related to the 12V battery.

Here is what I discovered:

There seems to be no need for the 12V battery these days. With it disconnected, I could still get in the car, even listen to the radio. Use the FOB. No need for the 9V battery either. There was a message on the screen that the 12V battery is disconnected. I have no idea how that is detected, because here are the facts:

Battery voltage unconnected to anything=13.20 volts (lith 12V batteries are a higher voltage than L-A).
Battery cable voltage not connected to battery=13.20 volts
Tesla powered down, and car powered off under "security" , 13.20 volts on cable to battery NOT connected to battery. This is unloaded testing, so it is possible that the current capacity is very low. But this voltage doesn't drop, so I don't think it's a capacitor holding the voltage or anything like that.

Even tested with trunk down using leads, 13.20 volts. Just wanted to make sure all was "normal",

13.20 Volts at all times, no matter how it is checked, with or without battery.

I will make the assumption that the 12V battery doesn't do much these days, if anything at all. Seems a DC2DCC is now really doing ALL the work, even with the car off and powered down.

I no longer see a need for the nine volt battery to be carried.

If the DC2DCC is on at all times, why is the 12V battery even needed? Am I missing something here?

I assume a recent FW update changed a lot of things WRT the 12V stuff.

Car I did the above testing on is my 2018 Tesla M3, LR, AWD.

Can anybody here explain these unexpected results from my testing?

-Don- Auburn, CA

 

[Tz00]

Can anybody here explain these unexpected results from my testing?

Simple: The car wasn't powered down.

When you change the battery you are supposed to pull the high voltage connector under the rear passenger seat. Do that with no battery connected and I guarantee you won't have voltage on the battery wire.

 

[DonTom]

Simple: The car wasn't powered down.

When you change the battery you are supposed to pull the high voltage connector under the rear passenger seat. Do that with no battery connected and I guarantee you won't have voltage on the battery wire.

Well, that explains part of it. I watched a you-tube WRT replacing the 12V battery that never mentioned the cable under the rear passenger seat. Doesn't seem to be necessary anyway--as long as we don't short out anything!

So it looks like the 12V battery has a trickle charge at all times. Even when the car is parked and everything is off.

BTW, when we select "power down" on the screen, what is it powering down?

-Don- Auburn, CA

 

[alee]

Well, that explains part of it. I watched a you-tube WRT replacing the 12V battery that never mentioned the cable under the rear passenger seat. Doesn't seem to be necessary anyway--as long as we don't short out anything!

If you have a 12V replace battery warning, that warning doesn't clear unless you disconnect under the rear passenger seat, wait a few min and reconnect. As best I can tell, the car remembers all the faults unless it loses power from the penthouse 12V connector. It's as close to a "fresh start" as you can get. In fact, when Ohmmu batteries were throwing false 12V errors, the workaround to do updates and temporarily clear the error was to disconnect the negative terminal, then disconnect the penthouse connector, wait a few min, and then reconnect.

The 12V battery is really just life support for the car when it's "asleep", and a way for the car to regulate power demand on the 12V system.

Upon exiting the car, the car will eventually go into a deep sleep mode. When you power off, it's basically the same... tapping the brake will "wake" the car again, so clearly the 12V is still on-tap. In fact, unless you disconnect the rear seat connector, as far as I can tell, an "Off" car still knows to top off the 12V battery so often.

 

[DonTom]

If you have a 12V replace battery warning, that warning doesn't clear unless you disconnect under the rear passenger seat, wait a few min and reconnect. As best I can tell, the car remembers all the faults unless it loses power from the penthouse 12V connector. It's as close to a "fresh start" as you can get. In fact, when Ohmmu batteries were throwing false 12V errors, the workaround to do updates and temporarily clear the error was to disconnect the negative terminal, then disconnect the penthouse connector, wait a few min, and then reconnect.

The 12V battery is really just life support for the car when it's "asleep", and a way for the car to regulate power demand on the 12V system.

Upon exiting the car, the car will eventually go into a deep sleep mode. When you power off, it's basically the same... tapping the brake will "wake" the car again, so clearly the 12V is still on-tap. In fact, unless you disconnect the rear seat connector, as far as I can tell, an "Off" car still knows to top off the 12V battery so often.

OIC. I did NOT have the message. I decided to replace the battery anyway with the lithium. But I did get the message that the 12V battery is disconnected when I had it disconnected. Byt that message went way as soon as I connected it back up.

When the car is "powered down" by the screen, it also says to tap the brake to wake up. I wonder if that activates the sleep mode but either I didn't give it enough time or woke it up via other means.

How long does it take for the car to go into deep sleep mode after it's locked up?

-Don- Auburn, CA

 

[Tz00]

wonder if that activates the sleep mode but either I didn't give it enough time or woke it up via other means.

How long does it take for the car to go into deep sleep mode after it's locked up?

When you use the screen to power off the car, you have to have the doors closed and at least 120 seconds without touching any controls or opening the door.

You can tell if the vehicle is asleep by listening for the loud sound of the high voltage contactor opening. You probably hear this sound most often when getting into the car after it has been asleep and the high voltage contactor closes.

The time for it naturally to sleep varies a lot, but Sentry mode and climate keeper all have to be off and the car locked and the cabin temperature not too hot.

Regardless, you won't be able to operate the vehicle without the 12V battery.

 

[alee]

How long does it take for the car to go into deep sleep mode after it's locked up?

I use TeslaFi, and the general behavior seems to be (I also have the Ohmmu):

If the car isn't driven (mine hasn't been driven for 4 weeks), the car wakes once a day for 1-2 minutes, and goes back to sleep. Presumably, it wakes, does some health checks, checks the 12V system, looks for any updates, and goes back to sleep.



Once a week, the car wakes for roughly 1-2 hrs, presumably to top off the 12V battery, and then goes back into deep sleep.



Here's another look at what the weekly top off looks like on a more fine resolution:

 

[smatthew]

When you use the screen to power off the car, you have to have the doors closed and at least 120 seconds without touching any controls or opening the door.

You can tell if the vehicle is asleep by listening for the loud sound of the high voltage contactor opening. You probably hear this sound most often when getting into the car after it has been asleep and the high voltage contactor closes.

The time for it naturally to sleep varies a lot, but Sentry mode and climate keeper all have to be off and the car locked and the cabin temperature not too hot.

Regardless, you won't be able to operate the vehicle without the 12V battery.

Some vehicles no longer power off. My 2018 LR RWD has not opened the contactor on power-off in over a year. Tesla is unwilling to troubleshoot the issue - I've had phone agents tell me the car no longer opens the contactor on power-off which is complete BS.

 

[DonTom]

My 2018 LR RWD has not opened the contactor on power-off in over a year.

Mine is also a 2018, LR but AWD M3.

I've had phone agents tell me the car no longer opens the contactor on power-off which is complete BS.

How do you know it's BS? Seems they can change just about anything with those FW updates. I don't think my contactor ever goes open. In fact, I didn't even realize there was one. Is this contactor built inside the battery as it is with my Zero electric motorcycles?

-Don- Auburn, CA

 

[Brock-WI]

I can see in teslafi our powered down between 15 and 45 minutes, not sure why it changes sometimes, but eventually it goes to sleep and it is obvious, you can hear the main contactor "clunk" open and no more whirring, pump or fan noises.

smatthew I am guessing you tried turning off sentry mode (that will for sure keep it awake) and remote connection to things like teslafi or other remote monitoring software can keep it awake as well.

As long as the car is "awake" it supplies power from the big pack for all the 12v stuff. Which always confused me that some people have had the car shut off with a bad 12v battery, maybe if a cell or two fails and it starts pulling to much power the car shuts off so it doesn't melt the bad 12v battery or becasue it can't maintain the 13.2v?

 

[ULEWZ]

The wife went into the Tesla and it opened the door, then rolled down the divers window and would not move. The DRLs were flashing, and the panel was dead. I had to show her the emergency release handle to get her out LOL. Then I called for service. After a while, the car app would show connected, and then the car said, need to replace battery soon. No warning up until then. The build date was 9/18 and now it is 6/7/21, so less then 3 years from install before it was dead. It was covered under warranty, so yay for that. The battery sides were bulging and there was a faint rotten eggs smell. All good for another 3 years I would imagine.

 

[TheCaptain67]

Same here. Got car in April 18 and got the 12V needs replacing message yesterday.

App said mobile service not available, and next SC appt was over 2 weeks out. Techs texted same day and converted to a mobile appt the following day. Swap only took the tech less than 10 mins. No charge, as still under warranty.

 

[DonTom]

As long as the car is "awake" it supplies power from the big pack for all the 12v stuff. Which always confused me that some people have had the car shut off with a bad 12v battery, maybe if a cell or two fails and it starts pulling to much power the car shuts off so it doesn't melt the bad 12v battery or becasue it can't maintain the 13.2v?

I heard something about a Tesla FW update (in another forum) that now keeps the DC2DCC always on, so perhaps we no longer have the need for the 9V battery. FWIW, my own experience with shorted cells in L-A batteries is that a shorted cell shows normal while being charged, but the voltage drops 2.1 volts as soon as the charging is removed, regardless of how long it has been charged.

-Don- Reno, NV

 

[Brock-WI]

Yes it would be nice if the software saw an error or problem with the 12v battery it would just keep the DC2DCC on all the time while continuously showing you the warning. While it is less common if a cell actually shorts out, the max you can charge it would be ~2v less that what it should be but I suppose a 12v with a bad cell could sit at 12v even with shorted cell.

I did have our front control arms replaced under warrantee about 2 weeks ago (no more squeaking, yaaaaa) and asked the service tech if I should just purchase a spare 12v battery, just in case, since we are 120+ miles from the service center. He suggested not to do that and that once the warning comes on you should have at least a week to replace it. And if I bought one it could sit for a year unused (even thought I would keep it charged).

 

[Oil Freedom]

A couple of weeks ago, I set up an appointment with Tesla mobile service to proactively replace the factory lead acid 12 volt battery in my Model 3 with a lithium ion 12 volt battery. It was partly a question to find out if they could do that now. Service said it's not available, so I cancelled the appointment. However, now I see that that refreshed Model S comes with a lithium ion 12 volt battery, which is terrific!

Soooo.... Does anyone know if Tesla is at least planning to offer lithium ion 12 volt battery replacements instead of lead acid batteries?