Model 3 12v Battery issues, monitoring, Aftermarket replacement

[Ravire]

After reading some more on another forum, including replies from the Ohmmu founder himself, I plan to buy one of their batteries sometime after my car hits 50k miles. That should be in about 12-13 months, after which my OEM battery will no longer be warrantied. If it can really last 4 years, that's worth the extra price IMHO. It should also reduce phantom drain, which is a nice bonus.

It’s only worth it for the extra life imo the difference is phantom drain in minuscule

 

[RKBA]

It’s only worth it for the extra life imo the difference is phantom drain in minuscule

Thanks for the first-hand info! I'm gonna claim I got it right when I said it was just a bonus.

 

[smatthew]

Thanks for the first-hand info! I'm gonna claim I got it right when I said it was just a bonus.

How much phantom drain do you think the 12V battery causes?

Let's do the math. Self-discharge on lead acid batteries is about 5% per month.
The Model 3 battery is 45Ah. 45Ah x 13 volts = 585 watts capacity
585 watts x 5% = 29.25 watts a month.
Or less than a watt a day.

Charing your cell phone at home will have more of a difference.

 

[RKBA]

What I read (in either this thread or one elsewhere) was that the phantom drain savings wasn't due to self-discharge but because of the vampire loads while the car is parked. Those loads take more from the SLA battery and therefore it needs to be recharged more frequently. The claim was that the 12V SLA battery gets recharged 2-4 times per day whereas the ohmmu was only being charged once per day at most. To be clear, I have no idea how reliable that information is.

 

[miimura]

What I read (in either this thread or one elsewhere) was that the phantom drain savings wasn't due to self-discharge but because of the vampire loads while the car is parked. Those loads take more from the SLA battery and therefore it needs to be recharged more frequently. The claim was that the 12V SLA battery gets recharged 2-4 times per day whereas the ohmmu was only being charged once per day at most. To be clear, I have no idea how reliable that information is.

The discharge curve for most LiFePO4 batteries is flatter than an AGM Lead-Acid battery. The Tesla vehicle is going to use it's own voltages to decide when to recharge the 12V battery. Just to pull some numbers out of thin air to illustrate the point, let's say the Tesla normally does 50% DoD (depth of discharge) and those same start and end voltages result in 80% DoD on the LiFePO4 battery. The factory battery is 45Ah and the Ohmmu battery is ">40Ah". 50% of 45 is 22.5Ah and 80% of 40 is 32. So, for these imaginary figures, if the factory battery recharged 3 times per day, the lithium battery would recharge 2 times per day. The self-discharge of each battery is inconsequential, the vampire drain is caused by 12V loads in the car that persist when the car is parked.

 

[GSP]

How much phantom drain do you think the 12V battery causes?

Let's do the math. Self-discharge on lead acid batteries is about 5% per month.
The Model 3 battery is 45Ah. 45Ah x 13 volts = 585 watts capacity
585 watts x 5% = 29.25 watts a month.
Or less than a watt a day.

Charing your cell phone at home will have more of a difference.

You forgot to include the higher round trip (charge + discharge) efficiency of Li-ion vs. PbA batteries. All of the vampire drain has to cycle through the 12 V, resulting in more energy loss from the HV battery for the less efficient PbA 12 V. This is how Li-ion reduces vampire drain.

You are correct about the 1 Watt-hour per day self discharge of the PbA battery being negligible.

GSP

 

[dcm3]

Is something like this useful?

Innova Battery Tester (Free Shipping)

 

[sh0719]

I decided to change the 12 volt battery before it left me stranded as the car is coming up on 2 years old this summer. After much measuring I figured that an Odyssey PC1100 would fit. I perfer Odyssey
batteries as I have received 10 plus years of service in several motorcycle applications. Also with standard battery prices going out site these are now reasonable. Battery cost was 226.79
Top post lug kit was 15.25 and shipping was free. The new battery fit in with no modifications. Specs are 45ah and 500 cca.View attachment 535663

Hi, I just purchased the same battery (Odyssey PC1100) and try to find the well-fit terminal stud post on the battery. Can you let me know which one did you successfully fit on? (I already failed to fit with 2 terminals and I am about to buying my 3rd trial one...) help me please.

 

[mikesyl27]

Had a 12 volt battery failure the other day. Had my M3 for less than 2 years. Fortunately I was at home and I needed to pull vehicle back in the garage. Got into the car and closed the door. No power at all. Had to use the door lever to open door. Contacted Tesla and they could not communicate with vehicle. They setup a tow to the service center. Battery was replaced quickly but did not think about the driver window after using lever. Drove the car home and did not immediately realize the window was down about 1/2 inch. The window would bounce down when rolled up. Setup a mobile service appointment. The window just needed a recalibration. Tesla does warn about using the lever and this is what could happen. Wanted to share this for others.

 

[jjrandorin]

moderator note: making this thread to consolidate the 12 volt battery failure discussion into a single thread going forward. I am not planning on moving historical threads into this one, as that would render it *unreadable.

Moving forward, experiences and discussion regarding the 12v Battery in the model 3 (failure, replacement, aftermarket options, etc) should occur here so people can find them in one place.

Some historical threads, so people can find previous discussions on the topic (which helped me decide to make a master thread on the topic).

Replace 12 volt battery
12 volt battery "back-up?"
Looking for a replacement 12 volt battery
Can a Tesla jump an ICE vehicle with 12 v battery? [Update: Tesla says NO]
How and when does the 12v battery get charged?
Vehicle shutting down please pull over safely [edit: 12v battery issue]
12v battery horror story
Replace 12 volt battery

Planning to replace 12V in M3 with Lithium Ohmmu battery.
What's with the Ohmmu 12V battery?
How does Ohmmu Battery perform in Hot Climate
Ohmmu Battery & 2020.28.6 update

*side note: In case people are curious on my statement on "not merging previous threads as it would make this one unreadable", I explained what happens in the following thread, the link below goes to the specific post. This is only for those who might be curious as to why I am not merging those threads above into this one.
Vehicle shutting down please pull over safely [edit: 12v battery issue]

 

[KenC]

Thanks to our moderator JJ.

If you are having a 12v problem or had one, it would be nice to track some basic info to see if there are any patterns to the premature failures.

vin - just the last 6 figs
Date of mfr on your door sill
Mileage
Any warnings, what were they?
If you had a warning, how long before failure?
Any other electrical oddities before failure?
Generally, how many hrs a day is your 3 unplugged?
Garaged, or outdoors?
State of residence to get an idea of the ambient temps.
Do you run Sentry?
Overheat protection?
Smart summon?
Anything else that might draw power while you’re not in the car? 3rd party dashcam? Radar?
Do you know your average phantom drain rate, miles/hr?
If you’ve looked at your 12v battery, what brand is it and date of mfr?

 

[Tz00]

If you are having a 12v problem or had one, it would be nice to track some basic info to see if there are any patterns to the premature failures.

And check the 12V battery with a volt meter to see what voltage it has when it is "dead". Is it low or open-celled at 0V.

 

[cruiserlarry]

My 2019 M3 got the "12V battery requires service" warning after it refused to boot up for about 10 minutes. Once I rebooted the car, everything fired up OK, but the warning continued, and a software update kept aborting (along with a "Driver window open" alert even though it's not open). I put a tester on the 12V battery, and it showed 14.2V and 92% capacity while connected to the car. I figured maybe the Voltage Controller was giving it a false high reading because it was still charging it - so I bought a replacement battery from Tesla, and installed it. No change, even after reboot - the "12V service required soon" warning stayed, as well as the window open alert. Put a tester on the new installed battery - 14.2V and 100% capacity. Tested the removed battery, and out of the car it shows 13.3v and 92% capacity; definitely not a bad battery, although the sides were a bit puffed out as if it had been overcharged...

Other than rebooting, is there something to reset after replacing the battery to eliminate the warning ?

 

[Tz00]

Other than rebooting, is there something to reset after replacing the battery to eliminate the warning ?

You have to fully power cycle the car (disconnect 12V battery, open contactor under back seat), to get rid of that warning, (or it may go away on its own eventually).

Here are detailed instructions: Tesla Model 3 Hard Reset | Mountain Pass Performance

 

[KenC]

Yeah, I would reset the HV contactor under the right rear seat.

 

[jjrandorin]

My 2019 M3 got the "12V battery requires service" warning after it refused to boot up for about 10 minutes. Once I rebooted the car, everything fired up OK, but the warning continued, and a software update kept aborting (along with a "Driver window open" alert even though it's not open). I put a tester on the 12V battery, and it showed 14.2V and 92% capacity while connected to the car. I figured maybe the Voltage Controller was giving it a false high reading because it was still charging it - so I bought a replacement battery from Tesla, and installed it. No change, even after reboot - the "12V service required soon" warning stayed, as well as the window open alert. Put a tester on the new installed battery - 14.2V and 100% capacity. Tested the removed battery, and out of the car it shows 13.3v and 92% capacity; definitely not a bad battery, although the sides were a bit puffed out as if it had been overcharged...

Other than rebooting, is there something to reset after replacing the battery to eliminate the warning ?

Did you choose to self replace the battery instead of calling for service because you are out of warranty or something?

 

[cruiserlarry]

Did you choose to self replace the battery instead of calling for service because you are out of warranty or something?

No - I choose to do it because Tesla didn't have an appointment available for 2 weeks, and I need to be able to make sure the vehicle was safe to drive, and would not cause my wife to be stranded. Very frustrated that I wasn't offered a mobile service appt, or any way to request it. I emailed 3 service centers, left voicemails for previous techs I've worked with, and responded to the text messaging appt confirmation, but no luck so far. I am a licensed auto tech, own a company that custom builds vehicles, and have 45 years auto mechanical / electrical / design/ fabrication experience (including many hybrids, etc) so I didn't think it would be difficult (changing the battery took less than 10 minutes, actually, including watching YouTube videos for confirmation). I did research first for any special conditions, and found many videos, etc, showing no additional steps required, including from Ohmmu batteries (which is different than the Model S and X procedure, which I've also done successfully). I tested the existing battery (which actually checked out fine electrically, but had bulged suggesting overcharging might be occurring), and tested the brand new Tesla battery, which was OK, prior to installing it. The vehicle is driving fine, but the warning remains despite the battery being good.

I'll do the suggested hard reset to see if that eliminates the issue, or if not, it might be a voltage controller problem - I'll have Tesla check the system since I kept my appt.

 

[cruiserlarry]

You have to fully power cycle the car (disconnect 12V battery, open contactor under back seat), to get rid of that warning, (or it may go away on its own eventually).

Here are detailed instructions: Tesla Model 3 Hard Reset | Mountain Pass Performance

Thanks - that did the trick lol...

 

[jjrandorin]

No - I choose to do it because Tesla didn't have an appointment available for 2 weeks, and I need to be able to make sure the vehicle was safe to drive, and would not cause my wife to be stranded. Very frustrated that I wasn't offered a mobile service appt, or any way to request it. I emailed 3 service centers, left voicemails for previous techs I've worked with, and responded to the text messaging appt confirmation, but no luck so far. I am a licensed auto tech, own a company that custom builds vehicles, and have 45 years auto mechanical / electrical / design/ fabrication experience (including many hybrids, etc) so I didn't think it would be difficult (changing the battery took less than 10 minutes, actually, including watching YouTube videos for confirmation). I did research first for any special conditions, and found many videos, etc, showing no additional steps required, including from Ohmmu batteries (which is different than the Model S and X procedure, which I've also done successfully). I tested the existing battery (which actually checked out fine electrically, but had bulged suggesting overcharging might be occurring), and tested the brand new Tesla battery, which was OK, prior to installing it. The vehicle is driving fine, but the warning remains despite the battery being good.

I'll do the suggested hard reset to see if that eliminates the issue, or if not, it might be a voltage controller problem - I'll have Tesla check the system since I kept my appt.

Thanks for taking the time to respond. Thats super unfortunate that they couldnt take care of it for you before that time. I also find it interesting that someone in your field, with your experience has a model 3 as a vehicle, when its likely you could have (or build) just about anything you wanted to.

 

[cruiserlarry]

Thanks for taking the time to respond. Thats super unfortunate that they couldnt take care of it for you before that time. I also find it interesting that someone in your field, with your experience has a model 3 as a vehicle, when its likely you could have (or build) just about anything you wanted to.

I also have a Model S, and a couple of custom off-road focused expedition vehicles....but I love new tech, everything automotive, and being an early adopter - and it only took one drive in a Tesla to know I wanted one (my first was a 2015 Model S, now a 2017 Model S and 2019 Model 3 and we have 2 Model Ys and another Model S in my immediate family). Aside from my off-road / business related vehicles, I'll never by an ICE car again. I'm just hoping the Cybertruck and Rivian make it to production soon, so I can replace my ICE trucks as well, and convert my expedition vehicles to EVs...