I have heard that if you run your battery all the way down until it is dead, not 0% but below that until there is no more juice, then it can be recharged but the separate 12 volt battery will have to be replaced. True or false?
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If battery is drained to 0%, the will 12V need to be replaced. True or false?
- Thread starter Vettepartz
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jebinc
Well-Known Member
EVFamilyGrins
Member
Depends on how long you leave your Tesla with a zero charge. If you run out of juice on a trip, you should be able to tow to a charger and recharge with no issues. The longer you leave it at zero and the older your 12 volt the greater the chance the 12 volt dies and possible damage to your HV battery.
That is a very unusual question, but a good one. The answer is basically true.
Here's what happens. One of the highest priorities they have programmed into the automated systems in the car is to not allow the huge main battery, which is worth many thousands of dollars, to get destroyed by going totally dead. So when the battery gets down very low, with only a self-preservation buffer left at the bottom, it will disconnect from the electrical system of the rest of the car and stay that way, isolated from anything that could drain any more energy from it. It can stay that way for many months without losing much. Obviously when it's like that, the 12V battery is going to run dead and be pretty damaged and need replacing, but that's only a couple hundred dollars, so is kind of the preferred thing to sacrifice.
It's not going to be really good for the main battery of course, because sitting at that low state of charge for a really long time is still kind of damaging, but it should be able to be recharged and used, with just some small degradation if it sat that way a long time. Here's a forum thread about this very question, with someone asking about getting a car that had sat for 18 months unplugged. Answers were pretty reassuring, and one person even mentioned that his own car had been purchased when it had sat for a year and gone dead like that and is still running with 240K miles on it.
Potentially buying a ‘17 90D that’s been garaged for 18 months but not plugged in
Hey everyone. I’m not a current owner, but there may be a situation opening up where I can buy a very low mileage (10k-15k) 2017 90D. Basically, the owner has been abroad for at least 18 months and the car has sat untouched - and unplugged in - since he left. It’s clear that the entire car...
teslamotorsclub.com
sleepydoc
Well-Known Member
True.
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Based on personal experience, I'd say this could be true. At least it was true 3+ years ago with a Model 3. We did a 600+ mile hypermile in an early Model 3 and drove it until it died. The car actually went about 50 miles beyond 0 IIRC and was running on the 12V battery. After the car died, it was pushed a couple hundred feet to the Supercharger and plugged in but it would never start charging even though the screen was still working. Tesla ended up having to replace the 12V battery.
This happened to my 8 week old Model Y yesterday.
I went on holiday and left my car parked. I don't have off-street parking so could not leave it plugged in and I wasn't aware of this issue (naively thought that a 2022 high end car could handle a 2 week holiday). When I charged the car up yesterday I got error messages that the 12V battery needed replacing.
Fine print in user manual explains that this is not covered by warranty so I'm liable for all charges.
Tesla's suggestion to me as a customer without off-street parking was that I pay to put someone else on the insurance (necessary in the UK) and ask them to drive and charge my car while I'm on holiday.
1. that doesn't sound like the way we will increase EV adoption and get the net zero transition to happen, and 2. it's a car, not a cat.
I went on holiday and left my car parked. I don't have off-street parking so could not leave it plugged in and I wasn't aware of this issue (naively thought that a 2022 high end car could handle a 2 week holiday). When I charged the car up yesterday I got error messages that the 12V battery needed replacing.
Fine print in user manual explains that this is not covered by warranty so I'm liable for all charges.
Tesla's suggestion to me as a customer without off-street parking was that I pay to put someone else on the insurance (necessary in the UK) and ask them to drive and charge my car while I'm on holiday.
1. that doesn't sound like the way we will increase EV adoption and get the net zero transition to happen, and 2. it's a car, not a cat.
sleepydoc
Well-Known Member
Beyond that, it’s kind of like having a goldfish bowl right next to a 500 L aquarium, connected by a hose and the computer lets the goldfish die from lack of water because it can’t figure out how to use the hose.Wow that sucks, I left my car unplugged for 10 days at the airport and only lost 3% charge.
Agreed it's not a cat and shouldn't need fed daily
I am going to guess that you also left either sentry mode, cabin overheat protection, or both on. If you didnt, you parked with the car at a very low state of charge before you left.
There is no other way that your car would "drain to zero" after 14 days. I can point to a few threads here where model 3 / Y owners have left the car for "weeks" / "months", and only lost 10-15% charge, like this one:
Friend opening car with no cellphone or wifi covarage
I'm away on a trip and I have my car parked in a garage with no cellphone or wifi coverage during my trip (car is not plugged in). My trip got prolonged and I'm worried that the battery will run out. I asked a friend to charge up the car. I granted the friend access to the car as a new driver...
teslamotorsclub.com
sleepydoc
Well-Known Member
I was under the impression that the problem @D-Vox experienced was with the 12V battery, not the high voltage battery. Either way, even if s/he left sentry mode or cabin overheat protection on they should shut itself off once the HV battery state of charge drops low enough.I am going to guess that you also left either sentry mode, cabin overheat protection, or both on. If you didnt, you parked with the car at a very low state of charge before you left.
There is no other way that your car would "drain to zero" after 14 days. I can point to a few threads here where model 3 / Y owners have left the car for "weeks" / "months", and only lost 10-15% charge, like this one:
Friend opening car with no cellphone or wifi covarage
I'm away on a trip and I have my car parked in a garage with no cellphone or wifi coverage during my trip (car is not plugged in). My trip got prolonged and I'm worried that the battery will run out. I asked a friend to charge up the car. I granted the friend access to the car as a new driver...
@D-Vox : can you confirm - were both batteries dead or just the 12V battery? Did you have any auxiliary services active?
Let's say he parked the car with 21%. Sentry and COP should have turned off at 20%. Still should be enough to last in the HV battery for two weeks. Must be the 12v battery that died. Probably not related to state of charge of the HV battery.
Since they are posting in a thread asking the question "does running down the HV battery to zero damage the 12v" and say "this happened to me, I parked on the street and...", it appeared to me that by saying "it happened to me" IT = 12v damage after running battery down.
Perhaps thats incorrect connecting of dots based on what they said, though.
Yes, both of those should turn off at 20%, but tesla has replaced plenty of 12v batteries on model 3s and Ys under warranty when the failure wasnt caused by the owner, so if tesla is not covering it, they are saying that it was caused by the owner draining the battery.
Putting all that together is where I got to what I posted.
whisperingshad
Active Member
There is something else going on with your car. While I agree these are not the longest lasting batteries, I have replaced mine once since I owned it, and it had not failed when I had it proactively replaced. 35k miles and almost 48 months. The location we both say we are in is the same general location too, so similar weather (although my car is parked in a garage, no idea if yours is).
(3) 12v batteries in 16 months sounds excessive unless you also have aftermarket things hooked up to it (like powered frunk / trunk, aftermarket sound systems, etc.
whisperingshad
Active Member
I garage mine, i at one point had underbody lights hooked up AFTER they had replaced the 1st battery so I have to pay for the 2nd battery. I disconnected from 12v after that. 3rd one then happened. Now they didnt die die, they came up with the error to replace, though last time it must have been worse as it had multiple errors and disabled the wireless charging.
While you don't say what the state of charge was when you left the car or when you returned (if the 12v battery was dead, then you can't tell the high voltage battery state of charge when you returned), here are a couple of things I experienced:
- during the pandemic, I was driving my Y about once a week. I was losing 7 to 8% PER DAY so most of the charge was going to phantom drain
- reading this forum, I learned that sentry mode was a big power sink. So I turned it off (I never enabled over-heat protection) and the phantom drain dropped to about 3% per day.
- I then read that the Tesla app on the iPhone was another reason why power was being drained. So when I go to the airport, I close the Tesla app. Now the power loss is maybe 1% per week.
So, if your problem was related to the phantom drain, there are ways to fix this power loss.
Another way to reduce energy is to turn off autopilot (summon?) standby or whatever it is called.I am going to guess that you also left either sentry mode, cabin overheat protection, or both on. If you didnt, you parked with the car at a very low state of charge before you left.
There is no other way that your car would "drain to zero" after 14 days. I can point to a few threads here where model 3 / Y owners have left the car for "weeks" / "months", and only lost 10-15% charge, like this one:
Friend opening car with no cellphone or wifi covarage
I'm away on a trip and I have my car parked in a garage with no cellphone or wifi coverage during my trip (car is not plugged in). My trip got prolonged and I'm worried that the battery will run out. I asked a friend to charge up the car. I granted the friend access to the car as a new driver...
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