Second service BMS issues

[GrahamH]

Second service BMS issues
We have an early gen1 ZSEV Exclusive, low mileage, that we registered from new in 2020. It went through all versions of the BMS updates because we were having timed charging problems and needed to ensure any vehicle software issues were eliminated. By August 2020 it was up to date and all working fine through its first service in Feb 2021.

1. Battery voltage at the end of equalisation for the past 12 months has been 448V
2. Warning regarding lack of Regen Braking on start-up after full charge
3. Regen is limited for the first 10-15 miles after full charge
4. Fast (7kw) charging works with doors unlocked

However, after second service in March 2022

1. Battery voltage at the end of equalisation has gone up to 449V (have done no DC charging).
2. No warning regarding lack of Regen Braking on start-up with full charge
3. Regen working immediately from full charge
4. vehicle needs to be locked for the charge cable to lock and the charge to start.

Whilst its unlikely that BMS has been downgraded, the symptoms indicate it has gone backwards. I believe the first set, after the 2021 service were correct. Does anyone else have any comments on the above 'symptoms' please?

I have attached the report of software versions provided to me after its first service.

 

[Kithmo]

Your first list, Feb 2021, sounds like the old BMS apart from point 1, the fully charged voltage, which should have been 456v. The charging whilst unlocked was a separate update to the latest BMS.
Your second list, after March 2022 sounds right for the last BMS update on points 1, 2 and 3.
It looks very much like you just had the charging unlocked update initially with a maximum HV charged voltage anomaly. Then in March they applied the latest BMS which doesn't include the charging whilst unlocked update and forgot to re-apply that after the BMS update.

 

[GrahamH]

Thanks for your reply. It had the 'bad' BMS update that ran the battery voltage up to 45x V but that was updated in August 2020 and after a few AC charges and equalisation settled down to 448V for over 12 months until the latest service.

Are you saying that the Regen normally works on a full charge (2) and there is not normally a Regen warning (3) on the latest version?

 

[Lovemyev]

However, after second service in March 2022

1. Battery voltage at the end of equalisation has gone up to 449V (have done no DC charging).
2. No warning regarding lack of Regen Braking on start-up with full charge
3. Regen working immediately from full charge
4. vehicle needs to be locked for the charge cable to lock and the charge to start.

1. Post BMS update - Base line first set by MG was to expect between 448 - 450 volts on the pack after a full charge and balance and a predicted mileage of 163 miles of range, in NORMAL mode and with BOTH trip meters set to zero. Also with NO 12 volt items running ( HVAC etc ) when the checks where done. Your 449 volts is absolutely fine ( 450 volts is the very best that you where likely to see ). The original factory software after a full charge and balance, was between 455 - 456 volts. The BMS update ( Release on the 15th Jan 2021 ) reduced the pack voltage down & increased the buffer / space at the top of the HV battery, is my understanding.
2. Normal.
3. Regen became available MUCH earlier after the BMS update even with a full charge - Normal !.
4. There is a "tick box" operation for one of the other modules, that needs to done to allow for A/C charging with the car unlocked, this is often missed when doing the BMS update.
This is a side update to the BMS update: specifically to the EVCC module of the car. Once this is installed, the car will charge both locked or unlocked.
Hope this makes sense ?.

 

[Coulomb]

IF you're really keen AND you have a fair chunk of time to devote to this, you could read this long thread where various firmware versions are discussed, as well as the means to check what versions you have now at home:

Project OBD2 - Mobile App v1.2.1 and later

Edited: Working mobile phone app (Android only) 👇DOWNLOAD👇 v1.2.1 out 02.03.21 👆DOWNLOAD👆 [ Coulomb edit 2: See also version 2.xx.5 in this post. ] [ Coulomb edit 3: The link immediately above now has version 2.8.0, also called V2.8. Discussion here. ] [ Coulomb edit 4: Version 2.9.0 is here...

www.mgevs.com

Note that there is a later version of the unofficial Thai app, so don't use the one in the first post. Follow the link in the first post to download the latest version.

If you're not bothered by the need to close the doors, you could just live with what you have. Maybe next service you'll get the EVCC firmware updated. BTW, in my 2021 ZS, with what I believe are the latest Australian firmwares, charging will pause when the doors are opened (though the dash implies that it's still charging), but charging will resume after a short delay. Perhaps you are noticing this temporary pause?