Replaced 12V battery, now have service alerts

[Zookkj]

A week ago I got the low voltage alert on my 2018 LR RWD and I found a replacement (AGMi listed as a replacement) at OReiley's. I didn't go the mobile tech route because the earliest appointment was too far out and I need the car to drive 2 hours to the airport this week. It worked fine for a day, then I got the following allerts: BMS_a170 (acceleration and top speed reduced) and BMS_a027 (power limited - ok to drive).

I checked the voltage of the new battery and it was at 14.3V, which I thought was high and I was reading that maybe the AGM battery was causing the problems, so I got a non-AGM replacement today and installed it and I'm getting the same errors. I did the hard reboot multiple times and I checked the battery voltage and it was also at 14.3V.
Could this be the reason I'm getting the errors? What should the 12V battery voltage be reading? Is a new Tesla 12V battery initial voltage that high?

I have an service appointment scheduled for after I return, but it's 2 hours away and I'd love to resolve this without taking a whole day off and not sure if I can get a loaner.

 

[Flybyglass]

2 things you can try is a hard reset and also check the service mode messages for more information on the BMS_a170 you have. Check service mode first since the hard reset will probably remove the messages. To check service mode:
1. Go to Software menu and press and hold for about 5 seconds the Model Tesla you have (there is an invisible button there). You will probably see a screen pulse under your finger.
2. The password is service lower case.
3. accept all the advisories.
4. on the main page you will see "Notifications button" (not the bell symbol at the top but a button). Select and more narrative o your messages will be there.
5. take a photo of all. (needed for service appointment and put in app incase they reappear).
6. Look at left margin for LV battery and select. A car map of LV charging should appear. Note anything not green and take a photo. Your 12 volt battery should be there showing the voltage and current amperage +/- being used.
7.Press and hold the red exit button at bottom and screen will exit service mode.

Next for the hard reset, this will follow what should have been the install procedure with the exception of no need to disconnect the positive terminal.

1. completely close the tesla app on your phone. (plus any other apps that could ping the car we want to car to power down).
1a unplug car from charger.
2. turn off climate control
3. remove any USB devices.
4. Drop windows and open driver door and RR passenger door and leave open.
5. open frunk
6. in safety menu select power off and wait 5 minutes (if completely powered off footwell lights should be dark - if not still ok to proceed).
7. remove frunk skirt covering battery as you did with the installation.
8. disconnect the negative terminal.
7. Under right rear passenger seat (there should be a small lever press sideways and just lift gently the one side of cushion). While holding up cushion remove the styrofoam cover over the HV disconnect (I suggest gloves as a precaution).
Press to side and down the gray lever to release the HV connection. Then using 2 hands on the top of plug (not grabbing wires to prevent damage) gently lift off the HV plug. You may hear the power relays "clunk" if car was not fully asleep.
9. wait a few minutes for all to de-energize.
10. Press down the HV plug back into place and raise the gray lock lever back into the lock position.
11. replace the foam block back onto HV plug.
12. press down rear seat and it should re-lock into place.
12. reconnect the negative terminal under frunk
13. reinstall frunk skirt covering battery
14. car should be rebooting or complete. Check notifications and it should be blank (for now).
15. reinstall any usb devices and place climate control back on close doors and windows.
16 reopen teslas app as normally used.
Car will go through a 6 hour battery initialization during which time it will be awake. Connect wall charger if have one.
After 6 hours car should sleep normally. This is most likely the period when messages could reappear.

Below is a DIY video from tesla outlining most of what said. Again no need to disconnect positive terminal. I have used Oreilly 51R AGM and DiehardEV AGM with no issues. If message returns not the 12 volt battery.

Model 3 Do It Yourself | Tesla

service.tesla.com

 

[davewill]

The only thing I'll add is that 14.3v sounds like a normal voltage when the car is on and charging the 12v battery.

 

[Zookkj]

I was able to obtain a 12V battery from Tesla via my FIL passing by the Columbus, OH, service center on his way to visit this weekend. After I installed the Tesla 12V and did all described above, the alerts are still present. I do have an appointment at the service center tomorrow afternoon, which hopefully will determine the cause. It was very coincidental with the battery change and I was hoping the OEM battery would resolve the issue. Online searching the codes several people needed new drive units or inverters. I will update after the service center appointment.

 

[Zookkj]

Tesla replaced the rear drive unit inverter under the drive unit warranty. They had the car there for over a week, but I had a loaner Model S for the entire time, which was very helpful. Thanks to the Sterling Service Center team for getting my 3 back to itself again.

 

[Ahmed Khalil]

I was able to obtain a 12V battery from Tesla via my FIL passing by the Columbus, OH, service center on his way to visit this weekend. After I installed the Tesla 12V and did all described above, the alerts are still present. I do have an appointment at the service center tomorrow afternoon, which hopefully will determine the cause. It was very coincidental with the battery change and I was hoping the OEM battery would resolve the issue. Online searching the codes several people needed new drive units or inverters. I will update after the service center appointment.

Could you update about the Alerts because i have the same case ?

 

[GtiMart]

I know in general it's better to charge a 12V battery before installing it. In an ICE car it prevents significant wear on the alternator to charge a dead battery all the way to full. Maybe the Tesla doesn't like to get an empty (or half-empty) battery to start with. Had you charged the 12V batteries you used before installing them in your car?