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

[brkaus]

BMW says hold my beer.

BMW Battery Registration​

BMW Intelligent Battery Sensor (IBS)​

On the plus side with Tesla at least you don't have to buy a scan tool to change the 12V battery. The BMW varies the charging based on the age and health of the battery. If you don't tell it you've put in a new battery it will assume it still has the old one in and won't charge it with a proper curve and will shorten the life of the replacement.

Friend of mine had an early one before you could get the aftermarket tools to reset. It had all sorts of problems. Hopefully better now.

Ahh yes, the ever reliable "Tesla service" who are definitely completely up to date on exact details on the newest firmware behaviors and can be asked any question about Tesla vehicles and you'll get a correct answer.
Did you ask them how many cars they have come in on a tow truck because of a dead battery in the last year?

I would expect there are still some 12v battery issues that could cause problems, like shorted cells. Keeping the 12v system held at 12v (or 13.8) in this instance might cause the battery to get hot.

 

[texas_star_TM3]

If people don't do that, how does "Tesla Service" know that it might die suddenly or might be good for a few days?

Miles of driving is completely irrelevant given how Tesla low voltage systems work. Anytime the car is "On," the 12V battery is completely unused. The car sitting asleep is rougher on the battery vs driving hundreds of miles. Unlike a ICE car, the battery mostly charges when it's not running, and is only loaded when it's not running.

why are batteries then failing after 2-3 yrs and most folks here get a battery replacement under warranty within the first 4 yrs? most ICE batteries (adverse regions not included) *easily* last 4-5 yrs ....

 

[gearchruncher]

why are batteries then failing after 2-3 yrs and most folks here get a battery replacement under warranty within the first 4 yrs?

What does this have to do with the thread? The question is if you should replace the battery proactively before you get a message or a failure.
You're saying that once you have the message, you might still have a sudden failure, but your only evidence is "Tesla Service Said."

I'm still looking for even a single example of someone being stranded by a dead 12V in the last 6 months after they made huge changes to the battery management firmware.

 

[gearchruncher]

Friend of mine had an early one before you could get the aftermarket tools to reset. It had all sorts of problems. Hopefully better now.

That would for sure a while ago, given the first BMW to require this came out 20 years ago.

 

[brkaus]

That would for sure a while ago, given the first BMW to require this came out 20 years ago.

Around 2000 I think. He eventually traded it in it was so problematic - Specifically the battery system. . I’m sure they have made lots of improvements.

 

[DrChaos]

why are batteries then failing after 2-3 yrs and most folks here get a battery replacement under warranty within the first 4 yrs? most ICE batteries (adverse regions not included) *easily* last 4-5 yrs ....

Because EVs use them differently than ICE cars, and it seems to be in a way that hurts their longevity. This is common to all EVs it seems, not just Tesla, all EVs have problems with lead-acid.

It was definitely the case with my previous BMW i3 which had a similar sized AGM 12V lead-acid battery; the favorite answer for anyone posting to i3 forums about any question about weird behavior and failures is "it's the 12V". (And it was almost $200 at the dealer for the part alone, and I reinstalled it myself)

Here's some threads on 12V Mach-E, they have polls about 12V problems. And there aren't any 5 year old Mach-es. (please excuse the snarky message on letmegooglethat, it wasn't mine or is intentional, it's the easiest way to show a google search result in a link)

Let Me Google That

For all those people that find it more convenient to bother you with their question than to google it for themselves.

letmegooglethat.com

re ICE cars: the 12Vs on the market have been evolved over 70 years to be optimal for the demands of conventional ICE cars, where the primary battery draw is for starting and is then charged up at 14.4v always while driving with an alternator. In normal use, they are always charged back up to nearly 100% after a quick current draw; that helps preserve their lifetime. (100% is good for lead-acid, bad for lithium ion). The ICE starter sudden current demand also seems to help desulfate the electrode plates.

EV accessory batteries aren't operated like that. They discharge deeper in sleeping conditions, and usually the main battery doesn't charge them during driving (to get better range) unless they're very low. They're smaller AGM batteries vs big flooded lead-acid batteries.

Anyway, I predict most EVs will transition to lithium-ion accessory batteries for all these reasons, as modern Teslas and Taycans have done. It just costs more up front.

 

[gearchruncher]

It just costs more up front.

Even that's debatable now. The Tesla 12V Li-Ion is only 99Wh. There's some pretty good data that Tesla is below $100 per kWh for cells- so this is $10 in cells.

A 400Wh Lead-Acid is costing them at least $50. Raw lead is $1 per pound nowadays, and a battery is >20 lbs.

 

[Watts_Up]

...most EVs will transition to lithium-ion accessory batteries for all these reasons, as modern Teslas and Taycans have done. It just costs more up front.

I believe that Prosche let you choose the type of battery to use, depending if you live in very cold weather location.

 

[P3dStealth]

If people don't do that, how does "Tesla Service" know that it might die suddenly or might be good for a few days?

Miles of driving is completely irrelevant given how Tesla low voltage systems work. Anytime the car is "On," the 12V battery is completely unused. The car sitting asleep is rougher on the battery vs driving hundreds of miles. Unlike a ICE car, the battery mostly charges when it's not running, and is only loaded when it's not running.

My car is a good example of that. My Tesla is a 2020 and has only 20,000 miles. My HV battery is barely used but my LV is also barely used now because it's new ; )

 

[hybridbear]

I'm wondering about proactive 12 volt battery replacement. Our 2016 S90D was built in late November & delivered in December 2016. It now has 106k miles & still has the original 12V battery more than 6 years later. The Service Center charges $165 for the part + $39 labor to replace it, the part # is ATLASBX U1 AGM(1480221-00-A). We drive the car daily, it's always plugged in if at home, and we park in a heated garage so the garage temp is never lower than about 55 degrees. Our car does not have access to wifi at home so it doesn't get to sleep. We also use TeslaFi & keep sentry mode on at home since we're parking in a shared underground garage. For those reasons the car doesn't get to go to sleep which may have helped keep the 12V battery charged for so many years... I'm not sure how those things play a role. Newer cars seem to have a way to go into Service Mode & see 12V battery health, but our older S does not show that info.

I don't want to "waste" money by replacing it unnecessarily, but since my wife uses the car daily for her small business & it's our only car we also can't afford to have a dead 12V battery strand us someday. What are ppl's thoughts on replacing it proactively & why or why not?

 

[dmurphy]

I'm wondering about proactive 12 volt battery replacement. Our 2016 S90D was built in late November & delivered in December 2016. It now has 106k miles & still has the original 12V battery more than 6 years later. The Service Center charges $165 for the part + $39 labor to replace it, the part # is ATLASBX U1 AGM(1480221-00-A). We drive the car daily, it's always plugged in if at home, and we park in a heated garage so the garage temp is never lower than about 55 degrees. Our car does not have access to wifi at home so it doesn't get to sleep. We also use TeslaFi & keep sentry mode on at home since we're parking in a shared underground garage. For those reasons the car doesn't get to go to sleep which may have helped keep the 12V battery charged for so many years... I'm not sure how those things play a role. Newer cars seem to have a way to go into Service Mode & see 12V battery health, but our older S does not show that info.

I don't want to "waste" money by replacing it unnecessarily, but since my wife uses the car daily for her small business & it's our only car we also can't afford to have a dead 12V battery strand us someday. What are ppl's thoughts on replacing it proactively & why or why not?

Kenny Rogers said it best.

“Ya gotta know when to hold ‘em, know when to fold ‘em, know when to walk away, know when to run.”

In your case - approaching 7 years old …. You’re somewhere between walking away and running.

Any vehicle - EV, ICE, Diesel - that’s a long, healthy, respectable period for a 12V lead acid battery.

I’d recommend replacing it, and soon. If your wife depends on the car especially, don’t wait for the battery to go south.

That kind of timeframe is most excellent for ANY automobile —- time to cash in the chips and let Tesla replace it. Best $200 you’ll spend this year. You’re playing with house money here —- you’re way up, time wise!

 

[metroplex]

My original factory battery in my 2009 Cobalt SS Turbo exploded in year 11 approaching year 12. I did a hot re-start in my driveway and when I cranked, I heard a loud explosion/boom in the trunk (factory location) enough that it sounded like someone kicking the trunk. Popped it, and saw all the smoke and smelled the acid. It was a PITA to clean up. Seems like a cell shorted out and caused a catastrophic failure.
My 2022 M3LR comes with a CATL 16V Li-Ion, but on the older Tesla with flooded low-voltage, I always wondered if it would be possible to source something like a Shorai Li-Ion to drop in as a replacement. My Ducati's Shorai is super light weight and compact, and doesn't self-discharge much at all in an unheated detached garage in the winter. I put on a Tender every 2 months during non-riding months since it doesn't discharge much.

 

[gearchruncher]

My 2022 M3LR comes with a CATL 16V Li-Ion, but on the older Tesla with flooded low-voltage, I always wondered if it would be possible to source something like a Shorai Li-Ion to drop in as a replacement. My Ducati's Shorai is super light weight and compact, and doesn't self-discharge much at all in an unheated detached garage in the winter. I put on a Tender every 2 months during non-riding months since it doesn't discharge much.

There are vendors that will sell you a drop in LFP battery. Search around here and you'll find them.
They're all currently in the process of basically going bankrupt because Tesla added detection for bad batteries, and is now catching 12V batteries before they fail and giving warnings. But guess what looks like a bad 12V lead acid battery? A LFP battery. So suddenly, with a SW update about a year ago, every one of their customers started getting warnings that their 12V battery is bad, and these warnings prevent the car from sleeping (because the only way a failed 12V battery can strand you is if your car goes to sleep).

You can always just leave sentry on 24/7 if you want to never get stranded (just be prepared for ~$500 a year in more electricity use)

 

[dmurphy]

I always wondered if it would be possible to source something like a Shorai Li-Ion to drop in as a replacement.

As @gearchruncher said (quite eloquently) - is it possible? Yes. Is it a good idea? No.

Tesla’s 12V battery replacement cost - parts AND mobile service - is extremely reasonable. There’s absolutely no good reason to go off the reservation here. It just leads to pain and suffering.

 

[metroplex]

As @gearchruncher said (quite eloquently) - is it possible? Yes. Is it a good idea? No.

Tesla’s 12V battery replacement cost - parts AND mobile service - is extremely reasonable. There’s absolutely no good reason to go off the reservation here. It just leads to pain and suffering.

What does Tesla's software do to determine if the low-voltage battery is "bad"? Other EVs like the Bolt have similar issues with their flooded lead-acid batteries dying prematurely leaving them stranded.
In this use scenario/application, a Li-Ion makes a lot more sense whether aftermarket LFP or the CATL NMC in the newer M3's - but not if Tesla's software makes them ill-suited.

 

[stopcrazypp]

What does Tesla's software do to determine if the low-voltage battery is "bad"? Other EVs like the Bolt have similar issues with their flooded lead-acid batteries dying prematurely leaving them stranded.
In this use scenario/application, a Li-Ion makes a lot more sense whether aftermarket LFP or the CATL NMC in the newer M3's - but not if Tesla's software makes them ill-suited.

I don't think anyone knows (and I'm sure the LFP sellers are trying hard to figure it out), but whatever detection they are doing, it doesn't like seeing LFPs.

 

[cbdream99]

What does Tesla's software do to determine if the low-voltage battery is "bad"? Other EVs like the Bolt have similar issues with their flooded lead-acid batteries dying prematurely leaving them stranded.
In this use scenario/application, a Li-Ion makes a lot more sense whether aftermarket LFP or the CATL NMC in the newer M3's - but not if Tesla's software makes them ill-suited.

I think Tesla determines by measuring the voltage and if it cannot be charged back to above the line then it will generate the warning at the high level. I have tried the ohmmu li-ion (also have to add shims to make a tight fit) and it is just like @gearchruncher says, just after 2 days I got a low voltage - schedule service to replace your battery message, and worse there is absolutely no response from ohmmu. I have some private exchange with a guy (owner?) in tmc here. He explained the technical problems and the difficulty that his company is facing, I felt bad for him but ultimately I haven't got any refund or updates like the multiple versions of 3/Y batteries that need a periodic reset. Oh well, wasted 400 bucks for a paperweight and ~200 bucks for a new battery from Tesla (I did it proactively). Good luck if you try something else, I very much want it to have more options...

 

[gearchruncher]

What does Tesla's software do to determine if the low-voltage battery is "bad"?

Nobody knows Tesla's exact algorithm. But it's not hard to see that a very smart algorithm that is looking for impedance changes, capacity changes, float voltages, or whatever else on a 6 cell flooded lead acid battery would freak out when it suddenly sees a completely different chemistry connected.

I mean, a human could easily tell look at a current curve under either charge or discharge and tell you if it's a LA or LFP, so it's pretty easy for the computer to do so too.

It's pretty neat that a 4 cell LFP and a 6 cell LA can pretty much be drop in replacements when all you have is a dumb fixed voltage charger (an alternator) and momentary start loads like in a car or powersport application. But that's not the way they are used in a Tesla, and it doesn't take much to tell them apart.

In this use scenario/application, a Li-Ion makes a lot more sense whether aftermarket LFP or the CATL NMC in the newer M3's - but not if Tesla's software makes them ill-

Only time will tell if it does make more sense- Tesla put a much smaller NMC in the newer cars, so they cycle it a lot more often, and of course it can't be charged below freezing and it has no heater. But either way, when Tesla made the change, they went to "15V" NMC, not "12V" LFP- and this required changes like different windshield wiper motors because not just everything that is happy at 12V would be happy at 15V. Hence why you can't just drop this in an older car and throw some software at it that knows to be happy with a different chemistry.

 

[STS-134]

I'm wondering about proactive 12 volt battery replacement. Our 2016 S90D was built in late November & delivered in December 2016. It now has 106k miles & still has the original 12V battery more than 6 years later. The Service Center charges $165 for the part + $39 labor to replace it, the part # is ATLASBX U1 AGM(1480221-00-A). We drive the car daily, it's always plugged in if at home, and we park in a heated garage so the garage temp is never lower than about 55 degrees. Our car does not have access to wifi at home so it doesn't get to sleep. We also use TeslaFi & keep sentry mode on at home since we're parking in a shared underground garage. For those reasons the car doesn't get to go to sleep which may have helped keep the 12V battery charged for so many years... I'm not sure how those things play a role. Newer cars seem to have a way to go into Service Mode & see 12V battery health, but our older S does not show that info.

I don't want to "waste" money by replacing it unnecessarily, but since my wife uses the car daily for her small business & it's our only car we also can't afford to have a dead 12V battery strand us someday. What are ppl's thoughts on replacing it proactively & why or why not?

Battery tester, small 12V power source, and a tool to open the emergency access port on the front bumper.

 

[brkaus]

I'm wondering about proactive 12 volt battery replacement. Our 2016 S90D was built in late November & delivered in December 2016. It now has 106k miles & still has the original 12V battery more than 6 years later. The Service Center charges $165 for the part + $39 labor to replace it, the part # is ATLASBX U1 AGM(1480221-00-A). We drive the car daily, it's always plugged in if at home, and we park in a heated garage so the garage temp is never lower than about 55 degrees. Our car does not have access to wifi at home so it doesn't get to sleep. We also use TeslaFi & keep sentry mode on at home since we're parking in a shared underground garage. For those reasons the car doesn't get to go to sleep which may have helped keep the 12V battery charged for so many years... I'm not sure how those things play a role. Newer cars seem to have a way to go into Service Mode & see 12V battery health, but our older S does not show that info.

I don't want to "waste" money by replacing it unnecessarily, but since my wife uses the car daily for her small business & it's our only car we also can't afford to have a dead 12V battery strand us someday. What are ppl's thoughts on replacing it proactively & why or why not?

My 12v in the 2017S gave a friendly warning and working a week w/o any issues whatsoever before they came out and replaced it in my garage. It lasted 6 years. Replacement cost $221 installed.

I'd say if you are going on a big trip or something, I'd get it replaced. But otherwise you're probably safe with the warning system and Tesla replacement when needed. Yes, your time is near, but it doesn't appear to be urgent by any means.

No wifi at home should not have anything to do with sleeping. At all. The other stuff does.