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

Well I took the battery into the service center and bought a new one. Got home, and I can't get the frunk open. I had to close it due to heavy rain today. I've tried my charger on the 10 and 50amp settings, as well as jumper cables from the new battery. No reaction, nothing. So this is turning out to be a huge hassle, and PITA. Definitely replace the battery before you get into this situation.
 
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stopcrazypp

Well-Known Member
Dec 8, 2007
13,021
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Well I took the battery into the service center and bought a new one. Got home, and I can't get the frunk open. I had to close it due to heavy rain today. I've tried my charger on the 10 and 50amp settings, as well as jumper cables from the new battery. No reaction, nothing. So this is turning out to be a huge hassle, and PITA. Definitely replace the battery before you get into this situation.
Check the polarity of the cables and your battery. People have popped the frunk even with A23 batteries or 8 AAs. I can't imagine a new 12V battery won't work unless it came discharged (not likely). When you disconnected the cables for the 12 battery in the car, hopefully you did not leave any shorted to the chassis.

You say "charger" so I suspect that you have an actual charger and not a dedicated jump starter. Chargers typically do some voltage detection before applying current, so may not do anything in this case with the battery completely disconnected. If you have a multimeter, it should be fairly easy to verify the voltage it is outputting. Basically 12V needs to be running through the jumper cables in the front.
 
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for what it's worth - sentry mode stopped working this morning when i re-arranged the car in the garage for better access for the mobile service tech (so he can work in the shade of the garage vs. blistering 104F outside when he comes). so in my case the system eventually disables sentry mode ... hoping it keeps the HV connector still open because otherwise you risk a bricked car. Car still works - but at this point with sentry mode no longer working and 2 days after the warning i definitely wouldn't want to drive the car anymore.
 
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for what it's worth - sentry mode stopped working this morning when i re-arranged the car in the garage for better access for the mobile service tech (so he can work in the shade of the garage vs. blistering 104F outside when he comes). so in my case the system eventually disables sentry mode ... hoping it keeps the HV connector still open because otherwise you risk a bricked car. Car still works - but at this point with sentry mode no longer working and 2 days after the warning i definitely wouldn't want to drive the car anymore.
The new software is supposed to not letting car sleep and keep the main battery as power to not need the 12V once the warning message appears. It does use a lot more battery. My coworker who can't charge at home said he lost over 100 miles before Mobile Service came to change his 12v.

I was thinking that since after the warning the software doesn't use the 12V, I should be able to drive the car right? So I ask the Mobile Tech the question. His response was "Yeah... I probably wouldn't drive it."
 
Well I took the battery into the service center and bought a new one. Got home, and I can't get the frunk open. I had to close it due to heavy rain today. I've tried my charger on the 10 and 50amp settings, as well as jumper cables from the new battery. No reaction, nothing. So this is turning out to be a huge hassle, and PITA. Definitely replace the battery before you get into this situation.
Oh wow. So now you are stuck with a new 12V outside the car? I wonder if Mobile Service could open the car, or it has to be towed to a service center.
 
The new software is supposed to not letting car sleep and keep the main battery as power to not need the 12V once the warning message appears. It does use a lot more battery. My coworker who can't charge at home said he lost over 100 miles before Mobile Service came to change his 12v.

I was thinking that since after the warning the software doesn't use the 12V, I should be able to drive the car right? So I ask the Mobile Tech the question. His response was "Yeah... I probably wouldn't drive it."
that's good to now. so putting on sentry mode isn't really needed anymore as a preventive measure from letting the 12V go flat once the system tells you the 12V needs to be replaced.

The answer from the tech makes sense as well ... I guess going forward (and especially being out of warranty) i would replace every 3 yrs pro-actively.
 
Oh wow. So now you are stuck with a new 12V outside the car? I wonder if Mobile Service could open the car, or it has to be towed to a service center.

Yes. So to close the loop on my ordeal. Prepping the house for sale and showings so my car was in the driveway. Went to pull it in that night, and it died completely once I got inside. Used my battery charger to power the tow hook leads, opened the frunk, found the battery had 4.5v. Put it on the charger and was still unable to open the doors. Let it charge overnight, still couldn't open the doors. Removed the battery completely - had to shut the frunk due to rain storms and house showings. Took the battery to Tesla after confirming in the app that I could just bring it in to swap. The service center was already closed at this point and they said I had to pay for the battery. Fine (it was only $85 which is very reasonable and one more reason to replace it proactively).

Took it home, connected my charger to the leads... nothing. Jumped the battery straight to the leads, nothing...

Checked the new battery's voltage - 12.1v. In the service manual it says anything under 12.4 to discard. Put it on the charger overnight. Tried jumping the battery to the leads this morning - SUCCESS! Hooked up the new battery, car operates as intended.

I suspect the charger didn't work with the 12v battery removed because it has a safety feature that won't energize unless it senses a load of a battery, and the straight battery jump didn't work because the battery Tesla sold me was dead.

Long story short, I'd glady spend $85 to prevent having to go through that ordeal again. My car was in my driveway and it was a huge inconvenience, if I'd been in a remote area or on the side of the road it would have been a nightmare.
 
Yes. So to close the loop on my ordeal. Prepping the house for sale and showings so my car was in the driveway. Went to pull it in that night, and it died completely once I got inside. Used my battery charger to power the tow hook leads, opened the frunk, found the battery had 4.5v. Put it on the charger and was still unable to open the doors. Let it charge overnight, still couldn't open the doors. Removed the battery completely - had to shut the frunk due to rain storms and house showings. Took the battery to Tesla after confirming in the app that I could just bring it in to swap. The service center was already closed at this point and they said I had to pay for the battery. Fine (it was only $85 which is very reasonable and one more reason to replace it proactively).

Took it home, connected my charger to the leads... nothing. Jumped the battery straight to the leads, nothing...

Checked the new battery's voltage - 12.1v. In the service manual it says anything under 12.4 to discard. Put it on the charger overnight. Tried jumping the battery to the leads this morning - SUCCESS! Hooked up the new battery, car operates as intended.

I suspect the charger didn't work with the 12v battery removed because it has a safety feature that won't energize unless it senses a load of a battery, and the straight battery jump didn't work because the battery Tesla sold me was dead.

Long story short, I'd glady spend $85 to prevent having to go through that ordeal again. My car was in my driveway and it was a huge inconvenience, if I'd been in a remote area or on the side of the road it would have been a nightmare.
Not much you could do this time since you can't open the doors, but if you are doing it yourself next time before the 12V fails, you need to disconnect the main battery (under the passenger's side rear seat) before you remove the 12V. I watched the Mobile Tech did that. Not sure if that's for safety of the vehicle or yourself, but probably should do it anyway.
 

Darmie

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Jan 13, 2016
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Clear Lake TX.
Hearing all the stories on our local FB group and reading here, I felt it was worth it to change out the one on our Model Y. It was an April build 2020. I know I probably could have went further but wanted to get it done well before 3 years. I had a Friday off end of last month. Drove up to the service/delivery center, and just walked in. I ask the young lady for a price and she quoted me $106. She ask if I wanted that installed. I ask what was the additional price. She kept looking on the computer and mention, "actually the price of the battery is $85". I mention sure, I'll have it installed. Thinking it may take some time to have this done, took a short walk to McDonalds for a quick sandwich and coffee. When I returned it was a short wait and I seen her drive the car around front. When she walked in with my key card, I ask if she did the install which she mention she did. I was really surprised how quick they got the car in and out to do something that was not scheduled. On the MY 2020 it's fairly easy to remove the cover and replace battery. Uh, there's a little more to it though.

At this price I'll plan on changing it out every couple of years for good insurance.

May need to do this on our Model X soon. It's a 2018 and has already had the battery swapped out under warranty once. It's a little more involved having to take out the tub but is doable.
 

stopcrazypp

Well-Known Member
Dec 8, 2007
13,021
9,299
that's good to now. so putting on sentry mode isn't really needed anymore as a preventive measure from letting the 12V go flat once the system tells you the 12V needs to be replaced.

The answer from the tech makes sense as well ... I guess going forward (and especially being out of warranty) i would replace every 3 yrs pro-actively.
When it drops to 20% sentry mode disables automatically. I'm not sure however if during this error situation it keeps the contactor connected though. The battery drain is going to be a lot more with contactor connected, so if you can charge the car it would be best to do so.
 

stopcrazypp

Well-Known Member
Dec 8, 2007
13,021
9,299
Yes. So to close the loop on my ordeal. Prepping the house for sale and showings so my car was in the driveway. Went to pull it in that night, and it died completely once I got inside. Used my battery charger to power the tow hook leads, opened the frunk, found the battery had 4.5v.
Yeah, 4.5V is way overdischarged, maybe even a cell or two has completely died. So basically not recoverable, and any jump starter may be even be dragged down by it if connected in parallel (a charger like yours has even less of a chance).
Put it on the charger and was still unable to open the doors. Let it charge overnight, still couldn't open the doors. Removed the battery completely - had to shut the frunk due to rain storms and house showings. Took the battery to Tesla after confirming in the app that I could just bring it in to swap. The service center was already closed at this point and they said I had to pay for the battery. Fine (it was only $85 which is very reasonable and one more reason to replace it proactively).
Yeah, $85 is fairly cheap, so luckily it's not that big a deal even out of pocket.
Took it home, connected my charger to the leads... nothing. Jumped the battery straight to the leads, nothing...

Checked the new battery's voltage - 12.1v. In the service manual it says anything under 12.4 to discard. Put it on the charger overnight. Tried jumping the battery to the leads this morning - SUCCESS! Hooked up the new battery, car operates as intended.
This is very informative to know even a battery barely at 12V OCV won't work. So basically any jump starter should still work though (usually they have OCV of 13V or higher).
I suspect the charger didn't work with the 12v battery removed because it has a safety feature that won't energize unless it senses a load of a battery, and the straight battery jump didn't work because the battery Tesla sold me was dead.
Yeah, basically exactly what I said upthread. Chargers detect if there is actually a battery attached (also usually checks for reverse polarity), so is not optimal for this situation. Jump starters are a better tool for emergencies.
Long story short, I'd glady spend $85 to prevent having to go through that ordeal again. My car was in my driveway and it was a huge inconvenience, if I'd been in a remote area or on the side of the road it would have been a nightmare.
If you are on the road, you can call the roadside assistance line for Tesla. If you live a populated area, usually they have a tow truck contracted nearby that can tow your car to a service center. If service center is closed, the tow truck driver may be able to jump your car to get things going temporarily. I used the service for a flat tire and it was quite convenient (service center was closed due to weekend, but tow truck has a loaner wheel available).
 
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and done... whole battery swap took a few minutes in my garage. super friendly Techs. He said in Texas 12V battery should last 2 to 3 years. so next time I'll swap out around 2.5 year mark. he said it's $120 for mobile to do it but it's that easy you can do it yourself. just disconnect main battery pack under rear passenger seat.
 
Question for those who got their 12V battery replaced by Tesla : how old was the replacement battery they installed (manufacturing date) ?

on 8/5/2022 (last week) the battery they installed was manufactured 9/6/2021 ... so exactly 11 months old. I was always told that after 4-6 months of sitting on the shelf.... 12V batteries aren't so good anymore and you shouldn't buy old/new stock. I frankly don't know where they even found such an old battery.

should I complain?
 
Question for those who got their 12V battery replaced by Tesla : how old was the replacement battery they installed (manufacturing date) ?

on 8/5/2022 (last week) the battery they installed was manufactured 9/6/2021 ... so exactly 11 months old. I was always told that after 4-6 months of sitting on the shelf.... 12V batteries aren't so good anymore and you shouldn't buy old/new stock. I frankly don't know where they even found such an old battery.

should I complain?
The date on top of the 12v says 04/25/2022.
 
The date on top of the 12v says 04/25/2022.
thanks. so yours was just a few months old. not nearly 12 months post manufacturing. I'm frankly a bit ticked off that Tesla is dropping in new-old stock batteries when making a service call. O'Reilly's wouldn't be selling nearly 1yr old 12V batteries and i doubt that Tesla warehouse is tendering to 12V batteries. I left a note in the "chat system" but doubtful they'll respond. So if you pay for a 12V battery swap out of warranty - better check you are not getting some old stock....
 
Are you referring to this item in Walmart? Wonder if it'll work in the MYLR?
Walmart 51R
It will work if your Model Y has the lead acid battery, but that battery is not sealed and vents directly out of the top covers (no connection to the vent hose that the Tesla has to connect to the battery). It will work, but any vented gasses that come out of the top of the battery when it charges could cause corrosion or buildup of the white lead sulphate on the battery terminals. The only batteries in size 51R that I have seen with a vent hose port are AGM batteries, which are more expensive.
 
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stopcrazypp

Well-Known Member
Dec 8, 2007
13,021
9,299
It will work if your Model Y has the lead acid battery, but that battery is not sealed and vents directly out of the top covers (no connection to the vent hose that the Tesla has to connect to the battery). It will work, but any vented gasses that come out of the top of the battery when it charges could cause corrosion or buildup of the white lead sulphate on the battery terminals. The only batteries in size 51R that I have seen with a vent hose port are AGM batteries, which are more expensive.
Yeah, what makes Tesla's OEM battery inexpensive is it's a "maintenance free" battery that has the vent hose port but yet isn't an AGM. I also haven't seen any in 51R with that port generally available in the US aftermarket that isn't AGM, so if you buy a generic one with that port, most likely it's significantly more expensive than the OEM one.
 
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The only limitation in the owners manual is minimum 33Ah rating. 51R batteries usually exceed this and the one you show has CCA of 500 and cranking amps of 625 so it is very likely above 33 Ah.

It's fine if the 51R exceeds the 33 Ah capacity. You're basically putting in a bigger capacity battery. Nothing will explode.
 
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