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"Proactive" 12v battery replacement - good idea or overkill?

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There have been a great deal of discussions about 12 Volt battery replacement, which kind to use, when to do it and proactive or not. Here is my most recent experiences and what I have learned.

First, when my model 3 was new in 2020 I replaced my 12 volt AtlasBX with an Ohmmu. The idea of having a lithium battery that could run for years vs. a basic lead acid seemed an easy decision. The Ohmmu worked flawlessly for months until Tesla started messing with the charging software.

Ohmmu developed a fix and replaced batteries. Well done.

Then Tesla hired a 12 volt battery engineer (Ohmmu knows the name of the engineer) who decided to add a battery over charge test to the software. The Ohmmu's Battery Management Computer (BMC) seeing the over voltage during the test would disconnect the Ohmmu to protect it (as it should) for about 5 minutes. But this caused multiple error messages. Back to the drawing board.

Ohmmu issued version or gen 3 of the Ohmmu. Many have stated worked great than about a month (including myself) then suddenly all kinds of messages again. Ohmmu is now working on Gen 4. My understanding is preliminary tests good expanding test group.

In the mean time, since I still had my factory AtlasBX on the shelf (now 2 years old but only cumulatively 10 days worth of usage) I charged it up (still had 95%) put a tester on it, it tested good and reinstalled while waiting for an Ohmmu fix. Messages gone and no warnings.

About 2 weeks after the install of the AtlasBX, I was having work done (seasonal brake maintenance) and was told by Tesla some battery messages were noted and they were going to "Proactvely" replace my AtlasBX. None noted by me either as warnings or notifications but maybe there is something they see that I can't. Battery replaced - no charge.

Which now raises the question:" How reliable is the AtlasBX". Now before everyone piles on with success stories there have been too many that have posted that warning to failure was either minutes to a day or so. That got me wondering if while waiting for a Ohmmu solution (I still think Lithium is the best way to go - so did Tesla on later 3/Y builds) what would be the best battery choice should it take months for an Ohmmu solution? AGM, EFB, or regular lead acid battery? AGM's are built for cycling (they are used on cars for example the have start/stop features even some have alternates that go offline until a certain voltage drop then re-engage to charge things back up to help mileage). EFB batteries are like a hybrid - they are a lead acid but designed for greater cycling. Then standard lead acid batteries (size 51R is what is needed). If one looks at the owners manual under specifications it will say the 12 volt must be 33 Amp/Hr rating or greater. The AtlasBX is 45 (and 625 CCA although CCA is not needed).

I was at Electrified Garage yesterday in NH (knowledgable good folks there). I asked which alternative battery to Ohmmu (which they used to install). I discussed the EFB (Enhanced Flooded Battery - see AutoZone for an example). AGM and regular. I pointed out that Orielly's for example published on the AGM it needs 13.8-14.6 volts to charge and 13.4 to 13.6 volts to float voltage. Otherwise with testing or monitors on the 12 volt have reported the charge voltage is 14.55 and the float is 13.1-13.2. The EFB had no such limits. So I asked the question to Electrified Garage "If a customer came in right now what battery would you put in?" Without hesitation the answer was "AGM". But I said "What about the charging requirements?" There answer: "the AGM is designed to cycle and all that will happen is the total charge will drop and at some point the cDC-DC charger will step up and recharge it". They had done some Tesla retrofits for a police department and got errors with the AltlasBX was loaded with accessories so they swapped out to AGM and no more warnings. I asked if others that had the AGM installed had any warnings and the answer was "no". They also said the Model 3 float charges to about 13.5v and Tesla has been trying to get the software right for charging since the Model S.

Another poster in a different thread stated he had gone to Orielly's because it was a weekend and put in an AGM a while ago. After something like 3 years 50,000 miles finally replaced it as a matter of routine maintenance. I think he replaced with the AtlasBX.

So yesterday I decided to put the AtlasBX on the shelf (as a backup) and install an AGM. I chose Orielly's but any of them meet spec of exceeding 33 Amp/Hrs. So far, no warnings (other than the ones that occur during removal process). Checked today, nothing overnight either. Prior to install, it was a 95% as delivered so I charged to 100% and tested. Tested good. We shall see but I have more confidence in the AGM than the AtlasBX while waiting for the Ohmmu solution.

So in conclusion I am running an AGM while waiting for the Ohmmu solution. As I has said earlier, I still think a lithium like Ohmmu is the best solution but at least I have more confidence in the AGM than the AtlasBX. I would caution that if Ohmmu had BMC issues, other lithiums SHOULD have the same problem as they all use a BMC. Some are claiming "no warnings" with their Lithium batteries but I will wait for an Ohmmu solution.
Thanks for sharing. Very informative. I don’t know why captain grumpy pants below is attacking you but there’s nothing in your post that justifies his rude response.
 
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Very informative. I don’t know why captain grumpy pants below is attacking you but there’s nothing in your post that justifies his rude response.
Look at Flybyglass' post history. Literally 1/3 of his posts include the word "Ohmmu" and over half are about 12V batteries, and he repeatedly posts the nonsense that the reason the Ohmmu has an issue is that the BMS takes it out of the circuit, and acts like it's something special that Ohmmu knows the name of the engineer that is improving Tesla's 12V tests. Yet he can't show any evidence why he's so worried about his 12V battery failing that he's willing to spend $600+ to "prevent" it. He even posts nonsense like the fact that we have to go to Ohmmu because the stock battery will no longer be produced, while himself heading to AutoZone and claiming he found a better battery on the shelf a few weeks later.

Don't fall for the FUD. Your 12V battery is fine. Especially don't go replacing it with some other chemistry than the one Tesla engineered into the car and expect it to work with fewer issues. For every battery that has failed within 4 years, there are 100+ that are just fine.
 
Maybe you should settle down and let people share about their experiences and stop being a bully. I see numerous posts in other Tesla groups about the issues he’s describing. You act like you are personally harmed by someone else sharing what they’ve learned, tried, etc. Switch to decaf or something. You’re embarrassing yourself.
 
I see numerous posts in other Tesla groups about the issues he’s describing.
Please link to one in the last 6 months, where the owner was stranded by a dead 12V battery. I keep asking, nobody responds.

Yes, it happened in the past. Tesla fixed it in firmware. This fix messed up Ohmmu batteries because a LFP "12V" battery IS a messed up 12V lead acid battery. The correct path here is not to petition Tesla to support LFP batteries, and stick an AGM in your car until that magically happens. It's to put the stock battery in your car and forget about it. His posts are not his "experience" - what experience is there in telling us all he stuck an AGM battery in his car this weekend? For all we know it will cause him issues in 3 days or 3 months. One experience he did share for sure is that he cheated Tesla out of a new 12V battery all because of his bad LFP battery, and then immediately put that one on the shelf, just like his previous one that was perfectly healthy. That's exactly the kind of stuff that will make Tesla even more sensitive to modifications to the car.

But since experiences are key: I've "experienced" that the LFP BMS is not the issue, since I have run an LFP battery without a BMS and it did the same thing. I also have 2 Teslas, one with a 4.5 year old battery and one with a 3.5 year old battery, and they both are working completely fine.
 
Please link to one in the last 6 months, where the owner was stranded by a dead 12V battery. I keep asking, nobody responds.

Yes, it happened in the past. Tesla fixed it in firmware. This fix messed up Ohmmu batteries because a LFP "12V" battery IS a messed up 12V lead acid battery. The correct path here is not to petition Tesla to support LFP batteries, and stick an AGM in your car until that magically happens. It's to put the stock battery in your car and forget about it. His posts are not his "experience" - what experience is there in telling us all he stuck an AGM battery in his car this weekend? For all we know it will cause him issues in 3 days or 3 months. One experience he did share for sure is that he cheated Tesla out of a new 12V battery all because of his bad LFP battery, and then immediately put that one on the shelf, just like his previous one that was perfectly healthy. That's exactly the kind of stuff that will make Tesla even more sensitive to modifications to the car.

But since experiences are key: I've "experienced" that the LFP BMS is not the issue, since I have run an LFP battery without a BMS and it did the same thing. I also have 2 Teslas, one with a 4.5 year old battery and one with a 3.5 year old battery, and they both are working completely fine.
Just because you don’t have a problem doesn’t mean others don’t. Every week there are posts in the numerous Fb Tesla groups about this issue. I personally know a few who were stranded because of zero warning when their 12V died while driving.

Furthermore, the entire purpose of these sites is to share information and ideas to help people solve things they’re dealing with. If you’re here to just attack people for what they experience because it’s different than your experience then you’re in the wrong place.
 
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Just because you don’t have a problem doesn’t mean others don’t. Every week there are posts in the numerous Fb Tesla groups about this issue. I personally know a few who were stranded because of zero warning when their 12V died while driving.
Yet again, nobody can link to one of these ubiquitous posts.

Like I keep asking, did it happen to the people you personally know in the last 6 months? Nothing before that is relevant, Tesla completely re-vamped their 12V failure detection and behaviors.

Super interesting that you suddenly came alive today after I pushed back and found this topic the first thing you needed to post was that flybyglass's post was very informative and all but one of your posts is about this.... And that flybyglass was able to react so quickly with a thumbs up... I see you are very passionate about this topic as well! You and flybyglass should get together, you both live very close to one another.
 
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Yet again, nobody can link to one of these ubiquitous posts.

Like I keep asking, did it happen to the people you personally know in the last 6 months? Nothing before that is relevant, Tesla completely re-vamped their 12V failure detection and behaviors.
Yep…a simple search in the first two Fb Tesla groups I’m in revealed no less than five posts each about problems with the 12v, all within the past 2-3 months. Why are you acting like a bully? It’s aggressive and rude people like you that make people think badly of Tesla drivers and make forums like this cringe-worthy. It’s one thing to disagree with someone but you take it to a bizarre level with rude, relentless attacks on people. Get some help buddy.
 
Yet again, nobody can link to one of these ubiquitous posts.

Like I keep asking, did it happen to the people you personally know in the last 6 months? Nothing before that is relevant, Tesla completely re-vamped their 12V failure detection and behaviors.

Super interesting that you suddenly came alive today after I pushed back and found this topic the first thing you needed to post was that flybyglass's post was very informative and all but one of your posts is about this.... And that flybyglass was able to react so quickly with a thumbs up... I see you are very passionate about this topic as well! You and flybyglass should get together, you both live very close to one another.
You’re creepy AF. How do you know where anyone here lives or how close they may be? I’ve been in this group for months and mostly search for information. I don’t need to post much since I find helpful info thanks to other users who share their experiences and learning. With your constant responses and following of people here it’s bizarre you don’t know that when someone replies or reacts to your comments and posts you get alerts. Why would it be odd for that person to react to a response to their post? It’s hard to believe the admins of this group allow you to be such a creep here. Total cringe.
 
The 12V battery can't cause this. She was able to unlock the car and get in, which means the 12V was working. Did you really have to do a hard reset (brake pedal, doors closed, etc), not a soft one? A soft reset only reboots the center screen, which again has nothing to do with the 12V.
Sounds like a simple software bug in the infotainment.
Car was unlocked in the garage. She only knew how to do a hard reset so went with that. You could be right about it being something other than a 12V problem that caused it, but after reading all the posts of failures leaving people needing a tow I just decided to get it done. I found it ironic (lucky?) that the error message appeared between the day I scheduled the appt and the appt itself.
 
She only knew how to do a hard reset so went with that.
Super interesting that you did get a 12V warning after, but as you can probably guess, you can't reset a car without power, so your 12V could not have hard failed like it has in other reports where it strands the vehicle.

I'm still interested what reset she did- two scroll wheels (soft), two scroll wheels with all doors shut, brakes, and longer press (full vehicle soft) or pulling the connector under the rear seat (hard reboot).
 
Super interesting that you did get a 12V warning after, but as you can probably guess, you can't reset a car without power, so your 12V could not have hard failed like it has in other reports where it strands the vehicle.

I'm still interested what reset she did- two scroll wheels (soft), two scroll wheels with all doors shut, brakes, and longer press (full vehicle soft) or pulling the connector under the rear seat (hard reboot).
Full soft from your description. Second time with this car, had to do it once about a year ago when the screen blanked out on us while on a road trip.
 
if that's in fact the case ... Tesla will pay for nearly every produced car with one mobile tech dispatch and 12V battery swap on their dime during the 4yr warranty period (assuming you aren't over 50k miles). doesn't seem true or sustainable as a component life. My guess is that under normal circumstances most batteries don't fail under 4yrs or 50k miles... 2018 and 2019 production cars are at the 3-4 yr mark and we would be reading about hundreds of issues here...
May not be a big enough sample size, but at my office, there are 4 of us who bought Model 3 AWD between 8/2018 and 11/2018. So far, 3 of us got the 12v need replacement soon warnings. The 4th guy hasn't got it yet, but he also rarely drive his M3 as he got 3 other cars and 7 motorcycles....
 
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May not be a big enough sample size, but at my office, there are 4 of us who bought Model 3 AWD between 8/2018 and 11/2018. So far, 3 of us got the 12v need replacement soon warnings. The 4th guy hasn't got it yet, but he also rarely drive his M3 as he got 3 other cars and 7 motorcycles....
i can deal with a "replace 12V soon" warning and a Tesla mobile tech stopping by a few days later. What i cant deal with is a full on failure and getting stranded somewhere with no warning. Didnt Tesla adjust SW for better 12V battery management in late 2019 ? So hopefully 2019 cars are less prone to early on failures as their batteries werent as abused as 2018 models (?)
 
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There have been a great deal of discussions about 12 Volt battery replacement, which kind to use, when to do it and proactive or not. Here is my most recent experiences and what I have learned.

First, when my model 3 was new in 2020 I replaced my 12 volt AtlasBX with an Ohmmu. The idea of having a lithium battery that could run for years vs. a basic lead acid seemed an easy decision. The Ohmmu worked flawlessly for months until Tesla started messing with the charging software.

Ohmmu developed a fix and replaced batteries. Well done.

Then Tesla hired a 12 volt battery engineer (Ohmmu knows the name of the engineer) who decided to add a battery over charge test to the software. The Ohmmu's Battery Management Computer (BMC) seeing the over voltage during the test would disconnect the Ohmmu to protect it (as it should) for about 5 minutes. But this caused multiple error messages. Back to the drawing board.

Ohmmu issued version or gen 3 of the Ohmmu. Many have stated worked great than about a month (including myself) then suddenly all kinds of messages again. Ohmmu is now working on Gen 4. My understanding is preliminary tests good expanding test group.

In the mean time, since I still had my factory AtlasBX on the shelf (now 2 years old but only cumulatively 10 days worth of usage) I charged it up (still had 95%) put a tester on it, it tested good and reinstalled while waiting for an Ohmmu fix. Messages gone and no warnings.

About 2 weeks after the install of the AtlasBX, I was having work done (seasonal brake maintenance) and was told by Tesla some battery messages were noted and they were going to "Proactvely" replace my AtlasBX. None noted by me either as warnings or notifications but maybe there is something they see that I can't. Battery replaced - no charge.

Which now raises the question:" How reliable is the AtlasBX". Now before everyone piles on with success stories there have been too many that have posted that warning to failure was either minutes to a day or so. That got me wondering if while waiting for a Ohmmu solution (I still think Lithium is the best way to go - so did Tesla on later 3/Y builds) what would be the best battery choice should it take months for an Ohmmu solution? AGM, EFB, or regular lead acid battery? AGM's are built for cycling (they are used on cars for example the have start/stop features even some have alternates that go offline until a certain voltage drop then re-engage to charge things back up to help mileage). EFB batteries are like a hybrid - they are a lead acid but designed for greater cycling. Then standard lead acid batteries (size 51R is what is needed). If one looks at the owners manual under specifications it will say the 12 volt must be 33 Amp/Hr rating or greater. The AtlasBX is 45 (and 625 CCA although CCA is not needed).

I was at Electrified Garage yesterday in NH (knowledgable good folks there). I asked which alternative battery to Ohmmu (which they used to install). I discussed the EFB (Enhanced Flooded Battery - see AutoZone for an example). AGM and regular. I pointed out that Orielly's for example published on the AGM it needs 13.8-14.6 volts to charge and 13.4 to 13.6 volts to float voltage. Otherwise with testing or monitors on the 12 volt have reported the charge voltage is 14.55 and the float is 13.1-13.2. The EFB had no such limits. So I asked the question to Electrified Garage "If a customer came in right now what battery would you put in?" Without hesitation the answer was "AGM". But I said "What about the charging requirements?" There answer: "the AGM is designed to cycle and all that will happen is the total charge will drop and at some point the cDC-DC charger will step up and recharge it". They had done some Tesla retrofits for a police department and got errors with the AltlasBX was loaded with accessories so they swapped out to AGM and no more warnings. I asked if others that had the AGM installed had any warnings and the answer was "no". They also said the Model 3 float charges to about 13.5v and Tesla has been trying to get the software right for charging since the Model S.

Another poster in a different thread stated he had gone to Orielly's because it was a weekend and put in an AGM a while ago. After something like 3 years 50,000 miles finally replaced it as a matter of routine maintenance. I think he replaced with the AtlasBX.

So yesterday I decided to put the AtlasBX on the shelf (as a backup) and install an AGM. I chose Orielly's but any of them meet spec of exceeding 33 Amp/Hrs. So far, no warnings (other than the ones that occur during removal process). Checked today, nothing overnight either. Prior to install, it was a 95% as delivered so I charged to 100% and tested. Tested good. We shall see but I have more confidence in the AGM than the AtlasBX while waiting for the Ohmmu solution.

So in conclusion I am running an AGM while waiting for the Ohmmu solution. As I has said earlier, I still think a lithium like Ohmmu is the best solution but at least I have more confidence in the AGM than the AtlasBX. I would caution that if Ohmmu had BMC issues, other lithiums SHOULD have the same problem as they all use a BMC. Some are claiming "no warnings" with their Lithium batteries but I will wait for an Ohmmu solution.
Excellent post.
 
Tesla Mobile Service came out this morning to replace the 12V. I timed it and it took him under 5 min from ringing my doorbell to finish the job. $85 for the battery and $34 for labor when they come to your house is really good price I think. My car just went over 50,000 miles in May. I wonder if it is under 50K, would they have replaced it for free? They did that for my Model X a few years back when it was under 50K miles.
 
One experience he did share for sure is that he cheated Tesla out of a new 12V battery all because of his bad LFP battery, and then immediately put that one on the shelf, just like his previous one that was perfectly healthy.
I fully informed the installer and he stated that Tesla insisted on replacing the battery due to a message. Since I can't see what they see for all I know there is some kind of recall. I didn't ask for it, they insisted on doing it. What am I supposed to say "Stay away and don't touch?" That is all the time I will spend on this.
 
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