12V Battery FAQ

[Misterrobot]

That's a bit strange, I don't think I've seen below 12.6V while driving. You're sure it was that low and not a false OBD reading from the adapter? How long did that last? I wouldn't worry about it yet, that could be some odd software thing or some kind of decay test.

could be a glitch. I haven’t reset or unplugged the reader in forever.

lasted half the trip. About an hour. It’s fine now.

Thee reader is a OBDLink CX Bimmercode Bluetooth 5.1 OBD2 Adapter for BMW/Mini, Works with iPhone/iOS & Android, Car Coding, OBD II Diagnostic Scanner

Sponsored

 

[Mach-Lee]

could be a glitch. I haven’t reset or unplugged the reader in forever.

lasted half the trip. About an hour. It’s fine now.

Thee reader is a OBDLink CX Bimmercode Bluetooth 5.1 OBD2 Adapter for BMW/Mini, Works with iPhone/iOS & Android, Car Coding, OBD II Diagnostic Scanner

I'm going to guess it was a glitch with the adapter or the reading getting stuck and not updating. If the battery voltage was held at only 12.0V for an hour, the SoC of the battery would have gone down as it discharged (it would not stay at 90%).

You can monitor the 12V voltage via the 12V port in the center console for independent verification of charging system voltage.

 

[fawzib]

Can I install a larger battery other than H3. I looked inside and seems like it can accommodate a bigger battery

 

[HughJazzol]

Can I install a larger battery other than H3. I looked inside and seems like it can accommodate a bigger battery

Other posts suggest that a larger battery will mess with software and modules.

 

[Mach-Lee]

Can I install a larger battery other than H3. I looked inside and seems like it can accommodate a bigger battery

See “Can I replace the stock AGM battery with bigger size?” in the FAQ.

Yes but it’s pointless and can cause further issues.

 

[redgrandam]

I had my battery replaced today. On my way home I plugged in my OBDII and the ‘12v battery reset (days)’ is still the same (it says 610). Does this mean they didn’t do the BMS reset?

I asked the service desk if they did it and I think the guy was confused about the question so never really got a clear answer.

 

[Mach-Lee]

I had my battery replaced today. On my way home I plugged in my OBDII and the ‘12v battery reset (days)’ is still the same (it says 610). Does this mean they didn’t do the BMS reset?

I asked the service desk if they did it and I think the guy was confused about the question so never really got a clear answer.

Correct, it should say 0 days since reset if they had just done it. So reset it yourself.

 

[redgrandam]

Correct, it should say 0 days since reset if they had just done it. So reset it yourself.

Thanks. Will do. Does it matter I was driving it around today? It wasn’t fully charged (but it’s not low either). I’m sure it wasn’t fully charged when they installed it either. It’s about 95% or so on the 12V when I reset it.

 

[Mach-Lee]

Thanks. Will do. Does it matter I was driving it around today? It wasn’t fully charged (but it’s not low either). I’m sure it wasn’t fully charged when they installed it either. It’s about 95% or so on the 12V when I reset it.

No, it’s charged enough to reset.

 

[ATL]

Correct, it should say 0 days since reset if they had just done it. So reset it yourself.

Same issue for me... Replaced 2 days ago. I note the value in Car Scanner but can't see how to reset it to 0. Do you know if that requires the pro version?

Is there a way to know if the shop performed the BMS Procedure?

 

[redgrandam]

Same issue for me... Replaced 2 days ago. I note the value in Car Scanner but can't see how to reset it to 0. Do you know if that requires the pro version?

It’s in the first post in this thread. Took only a few seconds to do.

Anyone know what the long term effects are of them not doing this reset? It seems to be charging the battery to a higher voltage now (which makes sense). Would it eventually figure it out itself?

 

[ATL]

I guess I wasn't quite specific enough, but I think I have my answer.

The huge and wonderful detail in post 1 doesn't specifically say (unless I missed it-quite possible) that the "days" counter I can see in Car Scanner is tied to the BMS reset procedure. It could be separate. If the reset procedure sets days to 0, then clearly the shop didn't do it, so that addresses the second question.

I share your curiosity about what happens when service departments don't do that simple thing.

 

[Mach-Lee]

I guess I wasn't quite specific enough, but I think I have my answer.

The huge and wonderful detail in post 1 doesn't specifically say (unless I missed it-quite possible) that the "days" counter I can see in Car Scanner is tied to the BMS reset procedure. It could be separate. If the reset procedure sets days to 0, then clearly the shop didn't do it, so that addresses the second question.

I share your curiosity about what happens when service departments don't do that simple thing.

It goes back to 0 days after a reset. Not resetting it will mess up the state of charge and capacity estimation of the battery.

 

[redgrandam]

It goes back to 0 days after a reset. Not resetting it will mess up the state of charge and capacity estimation of the battery.

Since we noticed they didn’t do it, I can only imagine the number of people that never get it reset. Will the car continue to have errors if it isn’t reset? Or will it adjust over time on its own eventually?
Just wondering what happens to those people that would have no clue.

 

[ATL]

It goes back to 0 days after a reset. Not resetting it will mess up the state of charge and capacity estimation of the battery.

Done-easy peasy. As usual... Thanks!

Sponsored