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

brkaus

Well-Known Member
Jul 8, 2014
8,793
7,456
Austin, TX
I see you are asking someone else. I can't see that it matters if the car is plugged in or not because the 12vdc battery is managed and charged by the HV pack anyway.
Anything is possible. The car could use a more power hungry algorithm if it knows it’s plugged in. Not saying it is, but since it’s software we couldn’t rule it out.
 
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Anything is possible. The car could use a more power hungry algorithm if it knows it’s plugged in. Not saying it is, but since it’s software we couldn’t rule it out.
YES, I am of the opinion that anything is possible for anything :) I was thinking if plugging in made any difference at all, then it might be that the car doesn't go to sleep as much. About 3 years ago, I monitored the battery charging for a week with a combination of plugged in and not plugged in, and I never saw a difference in how the hv pack was charging the battery, but the car didn't sleep as much at that time either. 3 years old information is ancient and not relevant in the EV market as you know. Who knows what happens with today's hardware and software.

My datapoint is worthless. Just to say for my old MX, I practically never plug it in at home. I only use superchargers. The 2 batteries lasted over 3 years. I recently proactively replaced it after 3 1/2 years before going on a cross-country trip.
 

texas_star_TM3

Active Member
Oct 28, 2019
1,251
1,929
Texas
just got a warning today.... electrical system backup power is unavailable / vehicle will consume more power / schedule service to replace low voltage battery / software will not update. July 2019 Model 3 AWD with under 30k miles on it. Not super impressed but at least it lasted 3 years and it's on Tesla's dime.

question: is it still safe to drive my wife to an appointment this afternoon right after receiving the message or best not to drive the car?
 
just got a warning today.... electrical system backup power is unavailable / vehicle will consume more power / schedule service to replace low voltage battery / software will not update. July 2019 Model 3 AWD with under 30k miles on it. Not super impressed but at least it lasted 3 years and it's on Tesla's dime.

question: is it still safe to drive my wife to an appointment this afternoon right after receiving the message or best not to drive the car?
When my M3 got the message, I didn't drive it for the week until 12v was replaced. When my wife's MX got the message, she was still driving it every day for a week and it was fine until Mobile Service came. I think the new software detection limit was made more generous so everyone is getting the message a bit earlier than a year or 2 back. I have no idea how much longer you could drive the car. I am thinking if the car is not going to sleep at all, you could probably drive it a long time as it is not using the 12v, but YMMV.
 
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just got a warning today.... electrical system backup power is unavailable / vehicle will consume more power / schedule service to replace low voltage battery / software will not update. July 2019 Model 3 AWD with under 30k miles on it. Not super impressed but at least it lasted 3 years and it's on Tesla's dime.

question: is it still safe to drive my wife to an appointment this afternoon right after receiving the message or best not to drive the car?
if you drive it, just be prepared to manually jump it(a23 battery and a jumper) or have it towed because it could leave you stranded.
 
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pilotSteve

Active Member
Jul 14, 2012
1,615
1,597
Prescott Az
I also can only offer anecdotal evidence. My 2016 Model S 90D, finally had the 12V battery low warning after 5 years and 125,000 miles. I plug in every night it is in my garage.
My '16 S90D gave the 12V battery low warning after 5 years also (but only 45,000 miles). I had it replaced at no further warnings (or worries for me). I have an Az garage that tends to get hot quite often so perhaps that accelerated the battery degradation. In any event the warning gave me advance notice and I had peace of mind and no inconvienence as mobile service replaced it a week or so later.
 

texas_star_TM3

Active Member
Oct 28, 2019
1,251
1,929
Texas
if you drive it, just be prepared to manually jump it(a23 battery and a jumper) or have it towed because it could leave you stranded.
yeah. not risking it. rather spend $60 on uber the next 2 days until they fix it with mobile Service Friday morning. the idea of getting stranded on the side of the road in 100F+ Texas weather isn't worth saving $60 to me. in the meantime i turned sentry on (= HV battery always on) so by Friday morning the car isn't bricked and needs a battery jump.
 
yeah. not risking it. rather spend $60 on uber the next 2 days until they fix it with mobile Service Friday morning. the idea of getting stranded on the side of the road in 100F+ Texas weather isn't worth saving $60 to me. in the meantime i turned sentry on (= HV battery always on) so by Friday morning the car isn't bricked and needs a battery jump.
Does it let you turn on sentry mode? I thought one of the "things" the message said was you cannot activate sentry mode. I haven't tried it. But the other thing it said was "no software update". Interesting enough, both of my car got a "software update" after the 12v warnings. I didn't try to install them though. Maybe it would still download it but won't let you install. I don't want to risk it so didn't click "install".
 
yeah. not risking it. rather spend $60 on uber the next 2 days until they fix it with mobile Service Friday morning. the idea of getting stranded on the side of the road in 100F+ Texas weather isn't worth saving $60 to me. in the meantime i turned sentry on (= HV battery always on) so by Friday morning the car isn't bricked and needs a battery jump.
It won't strand you on the side of the road because it won't fail while the car is awake or being used. I would still drive it, being careful not to let the car go to sleep if I leave it by turning on Sentry Mode or Keep Climate On. But everybody has a different risk tolerance, especially if they don't know exactly how the 12v system works in the Tesla.
 

texas_star_TM3

Active Member
Oct 28, 2019
1,251
1,929
Texas
Does it let you turn on sentry mode? I thought one of the "things" the message said was you cannot activate sentry mode. I haven't tried it. But the other thing it said was "no software update". Interesting enough, both of my car got a "software update" after the 12v warnings. I didn't try to install them though. Maybe it would still download it but won't let you install. I don't want to risk it so didn't click "install".
yeah. it let me turn on sentry just fine but the battery is draining now accordingly...
 
Just to save me trawling through 19 pages, what's a "good" voltage? I'm taking mine in for a fix to the cameras, and I mentioned the battery (69 plate car, 2nd half of 2019 for you guys:p), and they've said voltage is over14v and you'll get plenty of warning. As I've only owned the car since December, it's possible (although unlikely) that it's been changed previously. Maybe it's purely luck of the draw? We do get some reasonable temp swings in the UK, -5 degreesC to 35 degrees C is probably typical throughout the year.
 
just got a warning today.... electrical system backup power is unavailable / vehicle will consume more power / schedule service to replace low voltage battery / software will not update. July 2019 Model 3 AWD with under 30k miles on it. Not super impressed but at least it lasted 3 years and it's on Tesla's dime.

question: is it still safe to drive my wife to an appointment this afternoon right after receiving the message or best not to drive the car?

I just woke up to an alert on my phone and check my alerts in my Tesla and have the same ones! Just requested to schedule service.

IMG_4298.jpeg
 
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texas_star_TM3

Active Member
Oct 28, 2019
1,251
1,929
Texas
I just woke up to an alert on my phone and check my alerts in my Tesla and have the same ones! Just requested to schedule service.

View attachment 836598
at least yours lasted 4 years... my 12V crapped out exactly on the 3yr mark (took delivery August 3rd 2019). which isn't particularly impressive... I've never had a factory new 12V fail in just 3yrs with under 30k miles.
 
at least yours lasted 4 years... my 12V crapped out exactly on the 3yr mark (took delivery August 3rd 2019). which isn't particularly impressive... I've never had a factory new 12V fail in just 3yrs with under 30k miles.
Your replacement should be free (under 4 years/50,000 miles). His replacement is $125 because it is "just" over 4 years.
 
Just had this happen to me last night. 2019 P3D with like 37k miles. Car was in the driveway as we got things prepared for showings (the house hit the market the next day). Got in my car to pull it back in the garage and everything died. Had to use the emergency door lever to get out. Pushed the door shut and proceeded to troubleshoot. It was/is the 12v battery but I have no way to open the doors, move the car, etc. If I'd had a kid in the back, I'd be breaking a window. Overall a pretty awful design on Tesla's part that the door handles are battery dependent. Even with a 12v charger on it, the door handles wouldn't operate. So, I'd say proactively replace it - because you can't simply "jump start" a Tesla - if it happens when you're on a trip you're in for a lot of inconvenience.
 
Just had this happen to me last night. 2019 P3D with like 37k miles. Car was in the driveway as we got things prepared for showings (the house hit the market the next day). Got in my car to pull it back in the garage and everything died. Had to use the emergency door lever to get out. Pushed the door shut and proceeded to troubleshoot. It was/is the 12v battery but I have no way to open the doors, move the car, etc. If I'd had a kid in the back, I'd be breaking a window. Overall a pretty awful design on Tesla's part that the door handles are battery dependent. Even with a 12v charger on it, the door handles wouldn't operate. So, I'd say proactively replace it - because you can't simply "jump start" a Tesla - if it happens when you're on a trip you're in for a lot of inconvenience.
You are one of the few this year that got a dead 12V without any warning messages! You can open up and hood using jump starter connected to the wires inside the little cover plate at your front bumper. Once you have the hood open, you could hook up the jump starter to the battery and the doors "should" work. You should watch some youtube video on it so you would be prepared next time... in 3 years or so.
 
You are one of the few this year that got a dead 12V without any warning messages! You can open up and hood using jump starter connected to the wires inside the little cover plate at your front bumper. Once you have the hood open, you could hook up the jump starter to the battery and the doors "should" work. You should watch some youtube video on it so you would be prepared next time... in 3 years or so.
You're correct about getting the hood open - that was simple enough. However even with the charger connected to the 12v battery the doors would not open. I even tried bumping it up to the 50amp 'start' setting thinking maybe it was a current issue. No dice. Even after being on the charger all night I still couldn't get the doors open. Then, randomly, once this morning I was able to open the driver's door - but nothing else worked. It only opened once though, none of the doors would open after that. Very strange.
 
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stopcrazypp

Well-Known Member
Dec 8, 2007
13,086
9,403
You're correct about getting the hood open - that was simple enough. However even with the charger connected to the 12v battery the doors would not open. I even tried bumping it up to the 50amp 'start' setting thinking maybe it was a current issue. No dice. Even after being on the charger all night I still couldn't get the doors open. Then, randomly, once this morning I was able to open the driver's door - but nothing else worked. It only opened once though, none of the doors would open after that. Very strange.
Depending on how far your 12V has failed and what kind of charger you have, the voltage on whatever charger you may have been using may be too low to bring it back. If it's a traditional charger it may start out at a lower voltage and try to charge it, which may not be enough. Basically if it provides enough voltage and current for the HV contactor to activate (and enough time for car to "wake up"), the car can connect the high voltage battery and that will take over the duties. I believe the new firmwares now detect 12V failure and keeps the HV on during those cases.

A jump starter with a built in battery may have an easier time (I have one from my old car that has a built in lead acid battery of its own, most smaller ones use lithium ion now) given they output a higher voltage.
 

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