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

We have 4 people in the office bought Model 3 AWD back in 2018. Some drove like 5000 miles per year, other could be 20,000 miles. Everything got the replace 12V message this year within 3 months of each others and all before 4 years. It's almost like it is on a timer.
I and someone I followed on Twitter also bought our Model 3 LR RWDs very early in 2018. He traveled all over the country with his and had about 140,000 miles on it early this year. At that time he got the alert to replace the 12v battery. Mine is currently at 95,370 miles and I'm still on the original battery.
 
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Durzel

Well-Known Member
Jul 17, 2019
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4,580
Bath, UK
Curious... Is the likelihood of the 12V battery failing a function of how much you drive? For example, if you drive your car only 15k miles total over 4 years is the 12V battery less likely to fail than if you drive the car 80k miles over 4 years?
I'm at the extreme end I guess as someone who has only managed to do less than 1500 miles a year in my car. Needless to say my car can be parked up for several days, asleep, without turning a wheel.

In recent months the car would wake up every 24 or 48 hours (to the minute) and then stay awake for 1-3 hours. When I queried this behaviour with Tesla they confirmed the car was waking up and then "maintaining the low voltage battery". I had noticed - via TeslaMate - that this behaviour was becoming more frequent, it used to be the case that the car would wake up every few days, then it would become every 48 hours, then every 24 hours, etc. I guess the colder winter months finished it off.

As said above if you drive the car it charges the battery as you're driving much like an alternator in an ICE does. If you're not driving, then the car will wake up once it detects the battery has dropped to a certain level. In simplistic terms - a car that isn't driven much will end up recharging the 12v from a lower voltage than one that is driven every day, or every other day, which means the duty cycle is greater.

I have no idea how this all works with the lithium battery in newer cars though.
 
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KenC

Active Member
Sep 4, 2018
4,855
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Maine
I and someone I followed on Twitter also bought our Model 3 LR RWDs very early in 2018. He traveled all over the country with his and had about 140,000 miles on it early this year. At that time he got the alert to replace the 12v battery. Mine is currently at 95,370 miles and I'm still on the original battery.
Wow, so basically it seems 12v life is pretty random. I'm over 40k, and 49months since date of mfr., I have a spare 12v I picked up at a SC, and carry a 9v in my pocket, and have been waiting for the alert ever since 36months, but I'm thinking it must be time to swap it out.
 
carry a 9v in my pocket,
If you really are carrying a battery around, carry an A23- it's a lot smaller, 12V, and will open the frunk just fine once or twice.
Even better, tape it to the inside of the bumper so you don't have to carry it everywhere.

Remember that you can always just use jumper cables off any car around too.

If you're that worried about it though, I would just replace the battery, especially if you have already bought one. That one sitting around is wearing out too.
 
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Durzel

Well-Known Member
Jul 17, 2019
5,397
4,580
Bath, UK
If you really are carrying a battery around, carry an A23- it's a lot smaller, 12V, and will open the frunk just fine once or twice.
Even better, tape it to the inside of the bumper so you don't have to carry it everywhere.

Remember that you can always just use jumper cables off any car around too.

If you're that worried about it though, I would just replace the battery, especially if you have already bought one. That one sitting around is wearing out too.
I never actually said the words you quoted, not sure where you got that from. I don’t carry around a 9v in my pocket :)

Thanks for the advice about the A23 battery though. :)
 
If you live anywhere it's extremely hot I'd recommend just replacing the 12v every three years. Every car I've had the 12v died at or around the three year mark. Apart from a late 90's ford, the battery in that outlasted the car lol. The $125 or whatever it cost at the time was well worth it vs going out after work to a dead car. It's happened in the past with my previous cars where I could at least easily get inside the car and pop the hood to get a jump. I didn't want to mess with it on a Model 3 and just put it down to maintenance and peace of mind.
 
Wow, so basically it seems 12v life is pretty random. I'm over 40k, and 49months since date of mfr., I have a spare 12v I picked up at a SC, and carry a 9v in my pocket, and have been waiting for the alert ever since 36months, but I'm thinking it must be time to swap it out.
From what i see it seems to be people who live in hot areas tend to need the replacement sooner then those that don't. I wonder we ran a survey of park it out in the sun all day vs a garage in a hot climate would that paint an even clearer picture of how soon the battery should be replaced
 
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Well I got real lucky.. After reading this thread bought a battery from Tesla 2 weeks ago, and put it in my garage to get to later. Wednesday evening (day before Thanksgiving) got the push notification that 12v battery needs to be replaced. Went out and put it in right then. Could not have come at a worse time, but since I had the battery right there it worked out fine.

2018 model 3 with 64k, 4 yrs and 4 months old.
 

KenC

Active Member
Sep 4, 2018
4,855
4,612
Maine
Well I got real lucky.. After reading this thread bought a battery from Tesla 2 weeks ago, and put it in my garage to get to later. Wednesday evening (day before Thanksgiving) got the push notification that 12v battery needs to be replaced. Went out and put it in right then. Could not have come at a worse time, but since I had the battery right there it worked out fine.

2018 model 3 with 64k, 4 yrs and 4 months old.
Did you go out and buy a lottery ticket?

Mine was 4yrs and 2 months old, on Saturday. I went ahead and replaced it with an OEM battery I had picked up a while ago. The weather was nice and I got tired of waiting for an alert, figuring it would come at the very worst moment.
 
We have 4 people in the office bought Model 3 AWD back in 2018. Some drove like 5000 miles per year, other could be 20,000 miles. Everything got the replace 12V message this year within 3 months of each others and all before 4 years. It's almost like it is on a timer.
Probably from the same batch. But even within the same batch you're going to have units that are uncommon parts of the bell curve.
If you live anywhere it's extremely hot I'd recommend just replacing the 12v every three years. Every car I've had the 12v died at or around the three year mark. Apart from a late 90's ford, the battery in that outlasted the car lol. The $125 or whatever it cost at the time was well worth it vs going out after work to a dead car. It's happened in the past with my previous cars where I could at least easily get inside the car and pop the hood to get a jump. I didn't want to mess with it on a Model 3 and just put it down to maintenance and peace of mind.
Just get a tester and test it regularly, like once every month to 3 months, and run a test immediately before any road trip. It's not going to go from healthy to dead in a matter of a week or two. The moment the tester shows the battery getting weak, replace it.
 
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Probably from the same batch. But even within the same batch you're going to have units that are uncommon parts of the bell curve.

Just get a tester and test it regularly, like once every month to 3 months, and run a test immediately before any road trip. It's not going to go from healthy to dead in a matter of a week or two. The moment the tester shows the battery getting weak, replace it.
That's just asking for trouble lol. It's happened to me with a previous vehicle. Battery is good two weeks later stone cold dead. I don't have time for that and no I've zero intention of testing the battery every other day or week just to save a few $ I'm just not that cheap.

My advice here where it's extremely hot, don't be cheap and pay the money for the peace of mind or risk it playing the "will it or won't" it lottery. It's great when your winning that gamble and worth the $ when your stuck on the side of the road needing a jump. My time is more valuable than standing about waiting for a jump/tow knowing if I were proactive and not reactive I wouldn't be stuck or thinking about it.
 
That's just asking for trouble lol. It's happened to me with a previous vehicle. Battery is good two weeks later stone cold dead. I don't have time for that and no I've zero intention of testing the battery every other day or week just to save a few $ I'm just not that cheap.
Which tester do you have? I'll add that to my list of ones to avoid. And what was the last measured SoH and SoC of that battery and how long did it sit without being charged?
My advice here where it's extremely hot, don't be cheap and pay the money for the peace of mind or risk it playing the "will it or won't" it lottery. It's great when your winning that gamble and worth the $ when your stuck on the side of the road needing a jump. My time is more valuable than standing about waiting for a jump/tow knowing if I were proactive and not reactive I wouldn't be stuck or thinking about it.
You realize that all electronic devices have a few instances that suffer from "infant mortality" right? Replacing the battery after x months does not guarantee that it won't die on you and just gives you a false sense of security.
 
It's great when your winning that gamble and worth the $ when your stuck on the side of the road needing a jump. My time is more valuable than standing about waiting for a jump/tow knowing if I were proactive and not reactive I wouldn't be stuck or thinking about it.
Let's not be hyperbolic about the way it can happen though. It will not strand you "on the side of the road". A 12V battery failure will never stop a moving Tesla. The only real way this happens is when the car goes to sleep, which is after it's off for ~15 minutes, and often even much longer.

What I find interesting is the huge interest in this topic combined with a complete lack of reports of this happening in the last year after Tesla improved detection. Last time I asked for examples of this, I got "look on local Facebook groups"

Who here knows of an unannounced 12V failure in the last year where the car operated fine one day and then was just dead the next?
 
I just took my 2020 M3 to SC with original battery, they checked battery, said it was going bad and replaced it for free.
Pretty much did the same. Took it in for something else and asked them about paying for a replacement (mine was at about 3.5 years). After they were done the guy told me they replaced the battery but because it was still under warranty there was no charge.
 
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Adding my experience with my 2019 Model 3 LR AWD purchased August 2019.

The original 12v died after just before the 2 year mark of ownership. I had around 20k miles. It had just enough juice to allow me to open the frunk...then died hard. What was really annoying is I received no warnings that it was becoming a problem. Ugh.

At that time, Tesla had a 2+ week backlog on replacement 12v batteries. I needed a working car so went with the Ohmmu which shipped next day.

The Ohmmu worked well until this month when I got the dreaded "Your 12v battery must be replaced soon" alert. The battery was fine - it was the car's software that decided to no longer recognize the Ohmmu battery. I didn't bother with the procedure of disconnecting everything to remove the alert. I figured it would come up again soon anyway.

Contacted Tesla and they sent mobile service to me next day with a new Tesla-approved 12v.

I hope Tesla has improved the monitoring and charging logic for the 12v so it will at least give a few days warning before the next death....
 
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