12 volt battery question

[skierrob]

My 2020 LR AWD model 3 has 81K miles on it. Purchased December 2019. I've heard from some that the 12 volt starts dying about 3 1/2 years into ownership.
Question: Didn't Tesla change the type or model of battery they used sometime around the time I purchased in the hopes that it would extend battery life? I know there were lots of reports of premature "death" of batteries when I was buying. So I was hoping my vehicle would have a newer battery that might not have the same issues as "older" batteries that were placed into 2019 or 2018 Model 3's?

 

[jjrandorin]

Question: Didn't Tesla change the type or model of battery they used sometime around the time I purchased in the hopes that it would extend battery life?

No, they all have the same 12v until 2022, when they switched to the Li-Ion battery and rizen processor.

 

[AlanSubie4Life]

My 2020 LR AWD model 3 has 81K miles on it. Purchased December 2019. I've heard from some that the 12 volt starts dying about 3 1/2 years into ownership.
Question: Didn't Tesla change the type or model of battery they used sometime around the time I purchased in the hopes that it would extend battery life? I know there were lots of reports of premature "death" of batteries when I was buying. So I was hoping my vehicle would have a newer battery that might not have the same issues as "older" batteries that were placed into 2019 or 2018 Model 3's?

It’s possible that there were some bad batches. And it is likely Tesla has tweaked the charging profiles to extend life as much as possible so you benefit by being a couple years into that process. Also they have certainly improved battery failure protection so it is less of an issue now (many failures are gracefully caught and you can then drive the vehicle without concern with a failing battery - though of course for peace of mind you’d want to get it replaced quickly).

Eventually it will wear out. I wouldn’t expect more than 5-6 years but I guess we’ll see.

The car does not need the 12V (you can drive without one installed). It just has very high standby power when it does not. And of course there is the risk of what happens if the contactors ever do open for unknown reasons, which makes for higher anxiety.

 

[borland]

My 2018 M3 LR still has its original 12V battery. Not sure how long it will last, but I do check the static battery voltage occasionally with a multi-meter.

The way I check the battery voltage is to:

1. open the hood from the center display,
2. remove the charging plug from the charge port,
3. Power Down the HVAC from the Center Display,
3. Power Down the car from the center display ( Safety - Power-Down ),
3. exit the car, keeping the driver's door open,
4. remove the service panel under the hood,
5. remove the HVAC intake duct from it's mount to gain access to the 12V battery positive (+) post.
6. wait 5-10 minutes for all accessories to shut down.
7. Using the multi-meter, check the static battery voltage.

My 4-1/2 year old 12V battery reads about 13.2 volts with everything shut down, and about 14.2 volts with the car awaken from sleep.

 

[AlanSubie4Life]

My 4-1/2 year old 12V battery reads about 13.2 volts with everything shut down, and about 14.2 volts with the car awaken from sleep.

13.2V - will depend on how long it has been left. It starts around 13V fully charged (obviously depends on when exactly you catch it as it has to continuously discharge from the charging voltage of 13.5 to 14.5V - but 13V is when that decay slows down significantly). And goes to about 12.55V before charging starts (can take nearly 24 hours).

14.4V or so when actively charging and about 13.5V when in “sustaining” mode (float?), meaning car is awake and applying the charge voltage but not actively adding charge to battery.

 

[borland]

Yes there are many variables, like battery manufacturer, ambient temperature, battery chemistry.

I'm just looking for ballpark voltage to determine ability to hold a charge. Here's an example of voltage vs. state-of-charge in % for 12V AGM battery.