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12V Failure With No Warning

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Qbenjamin

Qbenjamin

Frugal But Classy!
Jan 7, 2017
1,214
780
Bravos
#1
Well, I'm not sure what happened, but I went to get in my car today and it gave me a weird message about there being a power failure (Jan '22 build). Car would not shift into D, so I left it. I assumed there was a 12V issue and checked the battery. Sure enough, it read 0.67V, this is on a 6 month old MYP. I immediately connected a trickle charger to it and let it charge for a few hours. Now the vehicle is totally unresponsive, doors won't open, nothing. Sigh...No ETA on when a mobile tech will be able to come out, so it'll be stranded in my garage for only God knows how long. :mad:
 
#4
Trickle charger will take a long time. you can try to jump start it from another car of a portable 12V JumpStart kit if it is necessary for you to drive. Long weekend means fewer mobile tech folks available for Tesla service. What is more concerning how the 12V battery gets to 0.67V within months from delivery. That needs to be de-bugged and fixed also along with battery replacement.
 
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#5
Qbenjamin said:
Well, I'm not sure what happened, but I went to get in my car today and it gave me a weird message about there being a power failure (Jan '22 build). Car would not shift into D, so I left it. I assumed there was a 12V issue and checked the battery. Sure enough, it read 0.67V, this is on a 6 month old MYP. I immediately connected a trickle charger to it and let it charge for a few hours. Now the vehicle is totally unresponsive, doors won't open, nothing. Sigh...No ETA on when a mobile tech will be able to come out, so it'll be stranded in my garage for only God knows how long. :mad:
Click to expand...
I'd disconnect the battery to charge it. It can't be good to subject the electronics to a lot of fluctuating low voltages...that said something is seriously wrong, and I would probably just wait for service rather than risk damaging something by trying charge or run it in this wierd state.
 
#6
Qbenjamin said:
Not sure that'll even work, we'll see how it fares tomorrow. I've had it on a battery tender for about 5 hours and it only went up to 4V.
Click to expand...
If that is the usual sort of battery tender it is probably supplying a little over 1A. Were your battery remotely healthy, and not being dragged down by something else in the car, it would have risen far above 4V in those 5 hours. So either your battery is in horrible shape, or something in your car is putting on a load in the neighborhood of an ampere when the 12V line is at 4V.

Both are awful. I hope your mobile tech can spot just what it is. I, personally, would not try to jump that car, nor to drive it anywhere until it is fixed.
 
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#7
So I did end up jumping the car on Monday and it started up no problem. It's measuring 15V now and even after I let it sit overnight, no change to the voltage (15V). Going to closely monitor it over the next week and see how it goes. The service center didn't respond via the app and I have no desire to drive over an hour away only to be told they can't find anything wrong with it. I tried to schedule mobile service, but it would only allow service center.
 
#8
Qbenjamin said:
So I did end up jumping the car on Monday and it started up no problem. It's measuring 15V now and even after I let it sit overnight, no change to the voltage (15V). Going to closely monitor it over the next week and see how it goes. The service center didn't respond via the app and I have no desire to drive over an hour away only to be told they can't find anything wrong with it. I tried to schedule mobile service, but it would only allow service center.
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I am curious, what is your daily/weekly charging routine? There was an issue with the 2021 Model 3 SR+ with the lithium iron phosphate LiFePO battery where the Model 3 would stop charging the 15V battery if the Tesla Model 3's battery management system was unable to determine the state of charge of the LiFePO battery pack, thought that the battery pack was at risk of becoming fully discharged. I believe the fix/recommendation was to charge the Model 3 SR+ to 100% at least once a week. I don't know if this has been fixed in the firmware but I have not read of any recent incidents where the Tesla vehicle stopped charging the 15V battery.
 
#9
jcanoe said:
I am curious, what is your daily/weekly charging routine? There was an issue with the 2021 Model 3 SR+ with the lithium iron phosphate LiFePO battery where the Model 3 would stop charging the 15V battery if the Tesla Model 3's battery management system was unable to determine the state of charge of the LiFePO battery pack, thought that the battery pack was at risk of becoming fully discharged. I believe the fix/recommendation was to charge the Model 3 SR+ to 100% at least once a week. I don't know if this has been fixed in the firmware but I have not read of any recent incidents where the Tesla vehicle stopped charging the 15V battery.
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Does this mean it's bad to change the 12V battery to li-ion? I just took delivery of a MYP late June and I believe it still has a lead acid 12V
 
#10
Mend0k said:
Does this mean it's bad to change the 12V battery to li-ion? I just took delivery of a MYP late June and I believe it still has a lead acid 12V
Click to expand...
If the vehicle was built in 2022 it has the new 15V lithium starting battery. For older Tesla vehicles that came with a 12V flooded lead-acid battery Ohmuu offers a Lithium iron phosphate replacement battery. (Currently Ohmuu is testing a revised version of their replacement battery for compatibility with the latest Tesla software.) Once Ohmuu releases the updated design you should be able to replace a 12V lead-acid battery in the Tesla vehicle with the Ohmuu battery (Tesla will only replace the OE battery when bad with another 12V lead-acid battery.)
 
#11
jcanoe said:
I am curious, what is your daily/weekly charging routine? There was an issue with the 2021 Model 3 SR+ with the lithium iron phosphate LiFePO battery where the Model 3 would stop charging the 15V battery if the Tesla Model 3's battery management system was unable to determine the state of charge of the LiFePO battery pack, thought that the battery pack was at risk of becoming fully discharged. I believe the fix/recommendation was to charge the Model 3 SR+ to 100% at least once a week. I don't know if this has been fixed in the firmware but I have not read of any recent incidents where the Tesla vehicle stopped charging the 15V battery.
Click to expand...
12V continues to fail every other day after a jump start, I have a mobile tech coming out on Tue to replace.
 
#14
Qbenjamin said:
Well, I'm not sure what happened, but I went to get in my car today and it gave me a weird message about there being a power failure (Jan '22 build). Car would not shift into D, so I left it. I assumed there was a 12V issue and checked the battery. Sure enough, it read 0.67V, this is on a 6 month old MYP. I immediately connected a trickle charger to it and let it charge for a few hours. Now the vehicle is totally unresponsive, doors won't open, nothing. Sigh...No ETA on when a mobile tech will be able to come out, so it'll be stranded in my garage for only God knows how long. :mad:
Click to expand...

Did you install any third party accessories that consume power?
 
#20
LoneStarEve said:
I’m curious how the car maintains the 12v battery. I assumed it constantly tops it up from the traction battery but I wonder if there is any linitation on that, especially if a bad software update that keeps retrying can cause the 12v to be drained.
Click to expand...
The primary battery is supposed to charge the low voltage battery. I also need to correct myself, its a 15v lithium battery in my car.
 
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