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Discussion Starter · #1 ·
Is there an easy way to tell which BMS you have without a visit to the dealer? I've taken delivery of my ZS, the dealer said it would come with a BMS check on pre-delivery inspection, which I assumed meant - if it wasn't running the latest BMS then it would be applied.

The car has arrived with 456v and 170 miles on Eco (which I'm happy with), this has been consistent with 2 charges. I can also charge with the doors unlocked and balancing isnt taking an unreasonable time.

A member has point out that due to the higher volts the car doesn't appear to have the latest BMS and that I should keep an eye on volts dropping, incase its the buggy BMS.

I had assumed that if the buggy BMS was running that the drop in volts would be instant and not accumulating over time...if a car is running the buggy BMS how soon do you usually start to notice issues?
 

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My experience with dealers suggests probably not. I'm now on my second dealer. Neither have been that successful applying updates and seem to have no idea as to what software it does actually have. Goes back in again for the 5th time in a year now to get it updated to the latest. Still missing comfort after 3 attempts, let alone BMS.
 

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I had my ZS serviced in October 2020 when it received the comfort and BMS updates.

As I remember it, it was several months before the fully charged voltage dropped from 456v to 439v but this was over a rather reduced mileage because of the lock down, I've still only done 1250 miles since then.

Rather counter intuitive, I would have thought that the voltage would have dropped immediately after the update, but that wasn't the case.

However the reduced voltage now proves that the faulty BMS update has been applied and my car is booked into my dealer on 23rd March to have the correct software installed.

Bombuzal that your car is reporting 456 volts at a full charge is ambiguous, you need to do several more charges to establish a voltage drop or you could simply give your dealer a ring and ask if it requires the new BMS update, it may not have even had the faulty update, MG apparently have a list of all cars with the faulty update so ask your dealer to check.

If your car hasn't even received the faulty update it still needs the latest update because MG have shaved the upper limit of the battery whilst releasing a similar amount at the lower limit to protect the long term use of the battery.
 

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Discussion Starter · #5 ·
I had my ZS serviced in October 2020 when it received the comfort and BMS updates.

As I remember it, it was several months before the fully charged voltage dropped from 456v to 439v but this was over a rather reduced mileage because of the lock down, I've still only done 1250 miles since then.

Rather counter intuitive, I would have thought that the voltage would have dropped immediately after the update, but that wasn't the case.

However the reduced voltage new proves that the faulty BMS update has been applied and my car is booked into my dealer on 23rd March to have the correct software installed.

Bombuzal that your car is reporting 456 volts at a full charge is ambiguous, you need to do several more charges to establish a voltage drop
Thanks!

Yeah, it will get its third charge tomorrow and I'll be watching it like a hawk for a bit yet. I will eventually get the new update but after reading all the issues, I'm in no rush until it has had sometime to get real world testing (that goes for any MG updates).
 

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I had my ZS serviced in October 2020 when it received the comfort and BMS updates.

As I remember it, it was several months before the fully charged voltage dropped from 456v to 439v but this was over a rather reduced mileage because of the lock down, I've still only done 1250 miles since then.

Rather counter intuitive, I would have thought that the voltage would have dropped immediately after the update, but that wasn't the case.

However the reduced voltage now proves that the faulty BMS update has been applied and my car is booked into my dealer on 23rd March to have the correct software installed.

Bombuzal that your car is reporting 456 volts at a full charge is ambiguous, you need to do several more charges to establish a voltage drop or you could simply give your dealer a ring and ask if it requires the new BMS update, it may not have even had the faulty update, MG apparently have a list of all cars with the faulty update so ask your dealer to check.

If your car hasn't even received the faulty update it still needs the latest update because MG have shaved the upper limit of the battery whilst releasing a similar amount at the lower limit to protect the long term use of the battery.
456V is a healthy BMS. Not the latest. But nevertheless that is okay. All ZS’s were delivered with that prior to the dodgy BMS. If the voltage is not dropping slightly every time you charge the car, then you are okay.
 
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