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

[android04]

Sure! But then when you get the 12V warning the replacement won't be free... So are you a lucky one that got an excellent 12v battery or an unlucky one who is one of the few who will have to pay for the 1st 12V replacement?

I don't mind having to pay for the 12v battery replacement just like I don't mind paying for tires, wipers, or cabin air filters. And I know how to handle the replacement and can find a battery anywhere. To me, having that knowledge is better than worrying about when or whether the battery will fail, and what to do when it happens.

Plus, I'm curious to see how long it will go before I get the message or it stops working. Maybe I will have the record after all .

 

[KenC]

Sure! But then when you get the 12V warning the replacement won't be free... So are you a lucky one that got an excellent 12v battery or an unlucky one who is one of the few who will have to pay for the 1st 12V replacement?

A 12v replacement is surprisingly affordable at Tesla, only $85, and no core charge. In my state, we pay an extra $20 for 12v battery recycling. It's pretty hard to find a 12v for as little as Tesla charges.

 

[P3dStealth]

I got the 12v warning while I was away on a trip. The warning came up on my app. The car was sitting about 30 days parked when it happened. I didn't get it replaced for another two weeks because I wasn't home. The car still worked fine when I got home. Just had the 12v alert on the screen all the time. So just because you get the 12v alert does not mean the car will go dead right away anymore.

Mobile tesla tech came out and replaced the battery in a few mins. Nice guy. Super quick job. I can't complain about Tesla service at all. He could have just left me the 12v and I still would have been happy they brought it to me.

So my conclusion is no you don't need to replace the 12v early. The system works better than any other car I've owned.

 

[Apprunner]

I got the 12v warning while I was away on a trip. The warning came up on my app. The car was sitting about 30 days parked when it happened. I didn't get it replaced for another two weeks because I wasn't home. The car still worked fine when I got home. Just had the 12v alert on the screen all the time. So just because you get the 12v alert does not mean the car will go dead right away anymore.

Mobile tesla tech came out and replaced the battery in a few mins. Nice guy. Super quick job. I can't complain about Tesla service at all. He could have just left me the 12v and I still would have been happy they brought it to me.

So my conclusion is no you don't need to replace the 12v early. The system works better than any other car I've owned.

Mine died right before my holiday travels so I waited a few weeks. However, I noticed the car never slept and would lose about 5% every 24 hours because it was constantly awake (probably to not rely on 12V). Of course, I noticed it wouldn't sleep before I left so I kept it plugged in but it was an interesting safeguard.

Wondering if you had the same experience.

 

[gearchruncher]

So just because you get the 12v alert does not mean the car will go dead right away anymore.

Correct. That has been mentioned in this thread multiple times. A FW update about a year ago improved detection and implemented defenses against a dying battery.

However, I noticed the car never slept and would lose about 5% every 24 hours because it was constantly awake (probably to not rely on 12V). Of course, I noticed it wouldn't sleep before I left so I kept it plugged in but it was an interesting safeguard.

This has also been mentioned many times. As long as the car detects it dying, it switches to keeping the HV online and supporting the car's 12V needs via the DC-DC instead of the lead acid.
But this does increase HV drain- in fact it's exactly the same as having sentry on, which also leaves the HV on anytime sentry is active. People don't realize it, but using Sentry 24/7 is about the same energy use as driving about 7,500 extra miles a year.

These changes are exactly why this "should I proactively replace my 12V battery" thread is a mess- people reporting experiences from years ago, as if nothing has changed. Then when I ask for someone to post any kind of dead car caused by a 12V battery in the last year, I get "It's all over facebook" yet somehow never get any links.

 

[dmurphy]

Then when I ask for someone to post any kind of dead car caused by a 12V battery in the last year, I get "It's all over facebook" yet somehow never get any links.

Quoting for truth.

I’m at 3 years and 9 months on my Model 3. Maybe for its 4th birthday, I’ll get it a 12V battery.

But then again, maybe I won’t.

Given how well the hv support works now, I don’t see the need to be prophylactic about it.

 

[P3dStealth]

Mine died right before my holiday travels so I waited a few weeks. However, I noticed the car never slept and would lose about 5% every 24 hours because it was constantly awake (probably to not rely on 12V). Of course, I noticed it wouldn't sleep before I left so I kept it plugged in but it was an interesting safeguard.

Wondering if you had the same experience.

Mine was still sleeping. I didn't even notice anything different other than the alert never going away on my screen and the car stops downloading updates. It tells you there is an update but also tells you it will not update until you replace the 12v battery.

 

[P3dStealth]

Anyone know how much the new lithium LV battery costs to replace?

I am not going to buy one I am just wondering who will end up having the better system. If the Lithium LV ends up lasting 8 years buts costs $400 and the lead LV lasts 4 years for $85 we still win.

 

[DrChaos]

Anyone know how much the new lithium LV battery costs to replace?

I am not going to buy one I am just wondering who will end up having the better system. If the Lithium LV ends up lasting 8 years buts costs $400 and the lead LV lasts 4 years for $85 we still win.

That's probably the right $, but I bet most of the lithium LV batteries will last as long until the car goes to the junkyard or is physically punctured. They probably set a low upper charging voltage, and with that the NMC batteries can last as long as LFP according to a paper I read. With time there will be calendar aging but even still that won't be bad, only a steady and slow degradation of capacity which will be mostly unnoticed.

The lead-acid batteries have a 100% guaranteed failure by 5 years. I bet Tesla is losing money on the service costs if they're charging only $85 including labor, but they're doing it for a good customer experience (unusually for them). The lithium LV battery will eliminate the most common reason for service calls.

 

[gearchruncher]

The lead-acid batteries have a 100% guaranteed failure by 5 years.

I'll take that bet and then win it right away with my 5.5 year old battery I have in my Model X, and the 13 year old battery I have in a BMW.
I'll win it again in a 6 months with the 4.5 year old battery in my Model 3.

They probably set a low upper charging voltage, and with that the NMC batteries can last as long as LFP according to a paper I read.

Storage voltage is not the only thing that wears out batteries. Equivalent number of recharges does as well. The new NMC "12V" battery is only 99Wh, while the lead acid was >400Wh.

Given a 500-1000 cycle general life for NMC, that's only 50-100kWh total out of this pack before it dies. To make it 10 years is only using 15-25Wh per day from the battery, which is only ~50mA.

My lead acid M3 draws WAY more than 50mA when sleeping.

 

[dusty22]

.A FW update about a year ago improved detection and implemented defenses against a dying battery.

Did Tesla make any announcements about that? I haven't seen anything in any of the updates over the past year. A dead 12V was my main worry about the car after I bought it and I promptly placed a little 12V in the tow hook receptacle to open the frunk just in case.

 

[gearchruncher]

Did Tesla make any announcements about that? I haven't seen anything in any of the updates over the past year. A dead 12V was my main worry about the car after I bought it and I promptly placed a little 12V in the tow hook receptacle to open the frunk just in case.

Elon did, does that count?

https://twitter.com/x/status/1305668355764809732

Also:

12V Battery Improvements Coming To Tesla Vehicles, Elon Musk Shares

Learning that a Tesla, which is full of lithium-ion batteries, also has an old-school 12V battery is often a shocker to people. But it does, and like in other cars, it's a part of the car that tends to die every few years, especially in blazingly hot places like Florida where I live.

cleantechnica.com

Also, these changes basically killed some companies, and tons of people have been looking into the firmware changes:

Ohmmu 12V Battery Feedback

i bought the Ohhmu battery for my Performance Model 3. It worked great until there was an update from Tesla. Apparently, Tesla is aware that this battery is not OEM and through the software quarantines it. Ohmmu tells me they are working on it, but no solution yet. I bought a Tesla battery...

teslamotorsclub.com

Longer term Ohmmu experiences?

Hi Looking at possibly buying an Ohmmu lithium (LiFePO4) battery to replace the OEM one in my Model 3. The car is approx 18 months old and from what I can see from stats it has started waking up to top up the 12v battery every 24 hours, so I don’t think it’ll be too long before it says it needs...

teslamotorsclub.com

I find it interesting that with all the mixed experiences with Tesla, what seems to have punched through for many people is "the 12V battery will strand you" to the point it's the first thing they consider with the car. I've had Teslas since 2016 and didn't even know it was a concern until I heard about the Ohmmu firmware issues and came to learn lots of people were buying them because of the dead 12V worry.

 

[dusty22]

Elon did, does that count?

I find it interesting that with all the mixed experiences with Tesla, what seems to have punched through for many people is "the 12V battery will strand you" to the point it's the first thing they consider with the car. I've had Teslas since 2016 and didn't even know it was a concern until I heard about the Ohmmu firmware issues and came to learn lots of people were buying them because of the dead 12V worry.

It sure does, I somehow missed his comment.

I did consider the 12V stranding issue. I had visions of trying to get inside a dead, locked car, in the middle of a parking lot, just before the sky opened up during a thunderstorm. I almost didn't order the car because of that; for a day or two anyway.

I did have a sense that Tesla did make improvements from reading posts here. I just wish that Tesla had made a formal announcement of an improved 12V battery warning update. It could have also given some details about how the car would stay awake until battery replacement That would have ended my concerns on this issue.

Thanks for the information.

 

[dmurphy]

I did consider the 12V stranding issue. I had visions of trying to get inside a dead, locked car, in the middle of a parking lot, just before the sky opened up during a thunderstorm. I almost didn't order the car because of that; for a day or two anyway.

Genuinely no more of an issue than an ICE vehicle. With the new lithium low-voltage battery, I'd say it's sigificantly less so.

Especially in the winter, we see sudden 12V battery failures all the time in ICE vehicles. At least the Tesla firmware is monitoring the battery in ways ICE manufacturers can only dream of.

 

[Timbo2]

At least the Tesla firmware is monitoring the battery in ways ICE manufacturers can only dream of.

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.

 

[⚡️ELECTROMAN⚡️]

I'll take that bet and then win it right away with my 5.5 year old battery I have in my Model X, and the 13 year old battery I have in a BMW.
I'll win it again in a 6 months with the 4.5 year old battery in my Model 3.

For the win I have a 14 year old battery in my boat \/

 

[texas_star_TM3]

My 12V lasted exactly just 3 yrs before the warning came. Per Tesla service - once the warning is there the car might die unexpected or is still good for a few days. unlike an ICE car you don't hear it struggling with starting the car which is a tell-tell sign that the battery is nearly dead...

i would definitely replace the lead-acid 12V battery every 3 yrs or when the warning comes...

 

[gearchruncher]

Per Tesla service - once the warning is there the car might die unexpected or is still good for a few days.

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?

 

[texas_star_TM3]

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?

how many have tested it out and ignored the "replace battery warning" for several hundred miles of driving?

 

[gearchruncher]

how many have tested it out and ignored the "replace battery warning" for several hundred miles of driving?

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.