When to Replace 12v?

[everydaychris]

I know you NEW Tesla's with the Li-Ion Battery don't have this problem.. But for those with the dinosaur 12v batteries, is there a certain voltage, time, miles you guys replace yours?
I know Tesla is supposed to be good at that and let you know to replace it soon. However, we are going to the Cybertruck event, DRIVING THERE, from CA, and I want Daddy Chill to be in TIP top shape.

I went to the secret service menu and no issues. When the car is on the 12v is running around 13v?
Currently at 3 Years 57k miles

Also, I DID let the HV battery die completely to see how many extra miles I got, VIDEO on that soon, but it was only dead for like 5 min before I plugged in.

TY!

 

[Ostrichsak]

You're way overthinking this and some of these extra efforts you're taking could actually be accelerating degradation. Running your battery completely flat is a good example. Unnecessary and potentially harmful.

You're also overthinking the 12v battery situation too. I've had 7 different Model S's now make it to over double your mileage before needing the 12v battery replaced. These are cars that spent a combination of their lives in the Pacific Northwest, California, Arizona and Colorado. In every case I was given ample warning and that warning lasted weeks or in some cases even months (appointment scheduled Tesla unable to get batteries) before the 12v battery was actually replaced. Who knows how long they would have gone before actually failing. My guess is quite a while given the relatively low demands on the 12v system in something like a Tesla versus an ICE car. Never once have I had an issue.

The supposed issue with the 12v system in the older cars is greatly over dramatized. A couple of people post having an issue and suddenly everybody thinks it's a known and common problem with these vehicles. It isn't. Every car that I've owned outside of Tesla has had a 12v battery die in a way that has left me stranded sometimes on very very very cold days. That's never fun.

For me, I'm not worried about it. We've driven these cars all over the country and some pretty lousy conditions too and the least of my concerns is the 12v battery. That's a welcome departure from how I would consider the low volt system in all of my previous ICE cars.

 

[ATPMSD]

Also, I DID let the HV battery die completely

NEVER DO THIS!!! This is how lithium batteries die. Tesla does have some protections against this, but this is asking for trouble. Plan your trips to never get close of 0%, in fact, I suggest when you hit single digits you should be at a charging station.

 

[dhrivnak]

I know you NEW Tesla's with the Li-Ion Battery don't have this problem.. But for those with the dinosaur 12v batteries, is there a certain voltage, time, miles you guys replace yours?
I know Tesla is supposed to be good at that and let you know to replace it soon. However, we are going to the Cybertruck event, DRIVING THERE, from CA, and I want Daddy Chill to be in TIP top shape.

I went to the secret service menu and no issues. When the car is on the 12v is running around 13v?
Currently at 3 Years 57k miles

Also, I DID let the HV battery die completely to see how many extra miles I got, VIDEO on that soon, but it was only dead for like 5 min before I plugged in.

TY!

So how much past 0 were you able to drive. and I would wait on the 12V warning. Mine first came after 4 1/2 years and not hard to change if needed.

 

[Pianewman]

Ostrichsak: Here in North Texas (with consecutive daily temps over 100f) , the North Texas Tesla Owners Group has had dozens of reports of spontaneous 12V battery failure, the vast majority coming with zero warning of any kind. Those that received warnings state that the battery then failed within 24-48 hours, and a few have stated that after warning, the 12V battery lasted an additional 10-14 days.

I don't believe the OP's concerns are over-rated, as the "warning" system doesn't seem to be consistent, so there might not be a definitive answer to his question about the predictable lifespan of the lead-acid 12V battery.

My personal opinion? I always pro-actively replace 12V batteries around 3 years, to avoid the inconvenience of a random 12V battery failure. The MY and M3 batteries are inexpensive and simple to replace.

 

[EVRider-FL]

3-4 years is normal (regardless of mileage). Ask service to check the 12V battery before your warranty expires and they might replace it proactively. I did that on my previous Model S, after the 12V died in my wife’s 3-year-old Model 3.

 

[Dennisis]

I got a warning right at the 2 year point and mobile service replaced it under warranty. With the AZ heat 3 years was max on my previous cars.

 

[Jerry Ham]

All of my prior ones (my 2017 Model S, my wife's 2018 Model 3, and my brother in law's 2018 Model S) have been at about 4 years and got the warning. Each was replaced by service within about 2 weeks and we never had any issue using the vehicle. Like another poster said above, I've had lots of ICE cars before 2017 and each of them left me stranded when the battery suddenly died.

Now I've got a 2023 MYP with the 16v Lion battery, so may have a different story in a few years. But the 12V ones have always been very good to us with plenty of warning.

 

[Ostrichsak]

Ostrichsak: Here in North Texas (with consecutive daily temps over 100f) , the North Texas Tesla Owners Group has had dozens of reports of spontaneous 12V battery failure, the vast majority coming with zero warning of any kind. Those that received warnings state that the battery then failed within 24-48 hours, and a few have stated that after warning, the 12V battery lasted an additional 10-14 days.

I don't believe the OP's concerns are over-rated, as the "warning" system doesn't seem to be consistent, so there might not be a definitive answer to his question about the predictable lifespan of the lead-acid 12V battery.

My personal opinion? I always pro-actively replace 12V batteries around 3 years, to avoid the inconvenience of a random 12V battery failure. The MY and M3 batteries are inexpensive and simple to replace.

Dozens? Shenanigans. Even if you guestimate is accurate, this is anecdotal at best. At least my anecdotal evidence is first-hand. These claims of people online are often half people parroting stuff they "heard from someone" once to join the conversation.

Texas is no different than Arizona and Arizona actually gets hotter absolute temperatures (electronics don't care about the "real feal" and are only concerned with absolutely temps) and Colorado has wild swings in temperatures year 'round. I'll stick with my own experience over 8 Teslas with a total of a million miles or so now.

Replacing a 12v battery in a Tesla as "preventative maintenance" is as silly as changing your motor oil every 500 miles or putting premium gas in a car that is tuned for regular. Do you also change your wiper blades monthly in case it rains that month?

I'll stick to letting the car tell me when I need a new 12v battery and not filling landfills needlessly or wasting money to replace perfectly good items. I promise that using this method I'll save a boat load of money and be left stranded FAR fewer times than I was in an ICE car.

This should be a non-issue if people would stop spreading FUD about it. This conversation is akin to someone starting a thread about the sky being green and 99% of the people see that and decide not to waste their time on something that is known to be incorrect. What you're left with is about a 50/50 blend of that last 1% which makes it seem like a bigger deal than it is. It's not.

You think Tesla would replace all of these 12v batteries under warranty when no other car manufacturer does if they were having to do so out of their own pocket as often as you claim? The same company that removed the UMC from new cars to save a few bucks and short-change all of the new Tesla owners? Yeah, that makes sense from an economical standpoint.

 

[Waltjo]

On my Model 3, the car issued a warning about the 12vold battery, set up a mobile service and the tech replaced the battery under warranty. Never had any failure related the aged battery.

 

[jjrandorin]

Replacing a 12v battery in a Tesla as "preventative maintenance" is as silly as changing your motor oil every 500 miles or putting premium gas in a car that is tuned for regular. Do you also change your wiper blades monthly in case it rains that month?

It happened enough (12v dead with no notice on model 3s) that it appears Tesla changed the charging algorithm several times trying to tune it, which is the genesis of all those Ohmmu issue threads. I do agree with you 100% on "dont use ohmmu", as over time I have seen more than enough to know that its not something anyone should be doing in a Tesla.

The 12v Lead acid battery in a model 3 is about $80-$90, not counting installation, so its not an expensive thing, and there have been enough different "anecdotal" reports of "my 12v failed and I got no notice" that it certainly is understandable people asking the question.

After the last changes to the charging algorithms that spawned the giant "ohmmu" threads, however, the number of those "12v died with no notice" threads in the model 3 subforum really died down, so I dont think this is nearly as much an issue as it was, however it definitely was an issue, so the hard line "this is FUD, / "why are you asking?" stance is a bit misplaced here, at least to me.

 

[Ostrichsak]

It happened enough (12v dead with no notice on model 3s) that it appears Tesla changed the charging algorithm several times trying to tune it, which is the genesis of all those Ohmmu issue threads. I do agree with you 100% on "dont use ohmmu", as over time I have seen more than enough to know that its not something anyone should be doing in a Tesla.

The 12v Lead acid battery in a model 3 is about $80-$90, not counting installation, so its not an expensive thing, and there have been enough different "anecdotal" reports of "my 12v failed and I got no notice" that it certainly is understandable people asking the question.

After the last changes to the charging algorithms that spawned the giant "ohmmu" threads, however, the number of those "12v died with no notice" threads in the model 3 subforum really died down, so I dont think this is nearly as much an issue as it was, however it definitely was an issue, so the hard line "this is FUD, / "why are you asking?" stance is a bit misplaced here, at least to me.

Because if the one vehicle that saw a slight uptick in occurrences received a repair years ago that all but eliminated this as an issue and people are still going around posting "dozens of people are having issues in our local groups... replace your 12v annually for peace of mind" type BS then it's FUD. No other way to slice it. We don't need that kind of a black eye on these cars because 1) it's a non-issue and 2) there are for more relevant issues that need to be addressed that this sort of ongoing and irrelevant static detracts from.

The next thing that happens is that people trying to do a little bit of research before buying a car come across current threads exactly like this spewing this nonsense and it makes it seem like this is a genuine issue they need to be afraid of. It's not.

p.s. Ohmmu is bovine excrement especially in a Tesla

 

[everydaychris]

Dozens? Shenanigans. Even if you guestimate is accurate, this is anecdotal at best. At least my anecdotal evidence is first-hand. These claims of people online are often half people parroting stuff they "heard from someone" once to join the conversation.

Texas is no different than Arizona and Arizona actually gets hotter absolute temperatures (electronics don't care about the "real feal" and are only concerned with absolutely temps) and Colorado has wild swings in temperatures year 'round. I'll stick with my own experience over 8 Teslas with a total of a million miles or so now.

Replacing a 12v battery in a Tesla as "preventative maintenance" is as silly as changing your motor oil every 500 miles or putting premium gas in a car that is tuned for regular. Do you also change your wiper blades monthly in case it rains that month?

I'll stick to letting the car tell me when I need a new 12v battery and not filling landfills needlessly or wasting money to replace perfectly good items. I promise that using this method I'll save a boat load of money and be left stranded FAR fewer times than I was in an ICE car.

This should be a non-issue if people would stop spreading FUD about it. This conversation is akin to someone starting a thread about the sky being green and 99% of the people see that and decide not to waste their time on something that is known to be incorrect. What you're left with is about a 50/50 blend of that last 1% which makes it seem like a bigger deal than it is. It's not.

You think Tesla would replace all of these 12v batteries under warranty when no other car manufacturer does if they were having to do so out of their own pocket as often as you claim? The same company that removed the UMC from new cars to save a few bucks and short-change all of the new Tesla owners? Yeah, that makes sense from an economical standpoint.

Only reason why I asked was because in our ICE car it would just die suddenly, no warning no nothing. I'll do a video on it when it does actually die and make sure to tag you haha

 

[Ostrichsak]

Only reason why I asked was because in our ICE car it would just die suddenly, no warning no nothing. I'll do a video on it when it does actually die and make sure to tag you haha

That's the important fact that people keep missing: Teslas have a feature built-in the monitors the health of your 12v battery. It can predict (with an alarmingly high amount of accuracy) when it will fail and warns you via a message on your dash weeks/months in advance.

Even in rare ICE cars that offer something similar, the demand of a battery to turn over an engine is dramatically higher impact especially in cold temperatures. Due to this, it's far more difficult to predict when a 12v battery in an ICE car will stop being able to start the engine. 12v batteries in a Tesla are for accessories (wipers, headlights, radio, at al) and the draw from these is very low comparatively speaking and consistent. Much easier to track anomalies and predict when that voltage will drop to a dangerous level.

Now, are there times where a 12v battery just fails for now reason and ahead of it's typical life expectancy? Of course. This is a known failure type in the 12v realm and it's the same for a Tesla as it is an ICE car because it's due to manufacturing differences. 12v battery duty in a passenger vehicle is a complex and complicated thing but it's far less complex, far less complicate and far more reliable in a Tesla than it is an ICE car due to what their job description is between those two technologies.

This should be a another non-issue but threads like this scare people away who haven't experienced them first-hand. Don't sweat it. Just drive the thing and it will let you know if/when you need to replace the 12v battery 99% of the time. People are so used to having to maintain an ICE car they almost search for items they can be proactive about and the reality is it's a waste. It feels weird at first, but just embrace it. The days of having to micromanage a machine to keep it on the road when you need it are over. All hail the EV!

 

[bo3bdar]

I can offer a little different perspective, since I ran across this recently. What happens when the 12V is dead? That's the key part.

The answer is that you can still drive the car, but having warnings on screen. The HV battery will remain always on, and the car will not sleep like usual. It's very much like having the car parked with Sentry enabled. In my case, it stayed live for a couple of days before I just drove directly to the Tesla service center, and they replaced the battery in 30 minutes, no appointment. Mine was 3 years 10 months from manufacture date before replaced.

I did not get any advance warning before getting error messages that the 12v was disabled and unusable. I don't agree that their software for warning you is accurate at all, it seems pretty terrible from my experience.

There are scenarios where a dead 12V can lock you out altogether, but these are pretty rare where the 12V has a catastrophic failure, not just wear out. In these scenarios, you need to pop the hood with a small battery, then jump or replace the 12V. If the car is live, and the high voltage contactors are engaged, you won't ever see this, it's only a combination of being asleep, and catastrophic 12V failure. You can't really avoid these types of failures, a new battery can fail as easily as an old one like this.


So even in the worst case, you can still get around, with on screen complaints, until you get to service. Since you are going to a place with good Tesla service (unlike say western Colorado where I went), you would not have any trouble getting it replaced.

So my recommendation would be to not worry about it for this trip, because you are within the service life of the battery still, and the penalty for being wrong is fairly low, in inconvenience, not stranding. The counter-argument is that this is such a cheap component, that stretching the life past where you are comfortable is saving some $20 if it lasts another year, and maybe you just spend that now for peace of mind.

This won't be replaced under warranty either way, it's considered wear-and-tear by Tesla service if it's made it past the 2 year mark.

 

[Pianewman]

Ostrichsak: I agree with much of what you posted.

However, I do NOT trust the Tesla 12V monitoring software, for the reasons I posted above, and will continue to replace the inexpensive 12V battery at or around 3 years. It's cheap insurance against an unpredictable, and inconvenient, failure.

Oh, FYI, I've never changed the oil in my ICE vehicles at any manufacturer's interval, since running full synthetic, for the past 40 years. I prefer to conserve natural resources, and change oil every 10k-15kmiles, getting 150k miles + out of EVERY engine I've owned. [Blackstone oil analysis every 50k miles]. My wiper blades last 2+ years, and I've never used premium fuel in any vehicle that doesn't require it.

 

[Stan930]

I had mine changed out a few weeks ago and my model three is a May build of 2021. Mobile service charged $130.00.

 

[cbdream99]

When my S turns 5, there was a time the car won’t sleep and the coolant pump is humming for hours, Tesla said everything is normal, tried the ohmmu crap, the pump stopped and noise gone but I also got 12v low charge needs to be serviced, so I ended up replace with Tesla battery and all problems solved, voltage looks . If there are enough complaints against earlier model 3/y, and there is an important long trip coming up with family, plus it’s been several years, changing it preemptively wouldn’t be a bad idea. Of course, if @everdaychris either way, enjoy the cybertruck launch

 

[rotarypower101]

If a person keeps a small 12vdc cell inside the front bumper jumper panel like the A123 cell or has a jump pack, is that enough power through that jump circuit port for the car to presumably open the contactor allowing the vehicle to then run off the PCS DC2DC even if the LV FLA cell has dropped below a low voltage threshold or even "completely failed" ?

Or is that jumper circuit isolated to the doors/entry systems exclusively? And a jump pack would be required to be applied directly to the LV battery terminals to activate the PCS?

 

[SageBrush]

Back in the day when I owned a 2018 Model 3, I pro-actively swapped out the 12. battery at 3 years old. I had two reasons:

1. To avoid unexpected 12v problems. If the early warning system is much improved that may not be a consideration today
2. My car usage events were often more than 24 hours apart and I was seeing high vampire drain. I reasoned that an old (but not dead) 12V may have been a contributor.