Our problem has been going on for months, so we've given up hope of it resolving itself. I contacted another dealer for advice this week. It seems our vehicle shouldn't have had the BMS update as it is for vehicles that were having problems with battery equalisation. (Ours was fine.) The original dealer washed their hands of it, saying we had the latest software, no fault found. Fortunately the second dealer is happy to investigate, so we'll be booking it in there soon-ish.
The first dealer who told you that your car should never have received the BMS because it was ONLY intended for cars that suffered only suffered from balancing / equalisation on their pack is total B/S sorry !.
Why - Because our previous Gen 1 ZS EV received the BMS update at our local dealer, while in having another small job done to replace the drivers door loom, under a MG service bulletin for the early models.
Prior to this update, we where running on the factory installed software and had NO problems with charging or balancing / equalisation of our HV pack before.
In fact, it was MG customer services that advised the dealer to apply the very latest software package to our car.
The BMS update was available to be applied to customers cars ( if required ) on the 15th Jan 2020 I believe is the correct date.
It was applied to our car the following day !.
We owned the car for approx another 12 months after the update was applied and then exchanged it for the face lift Trophy LR model.
I think you have done the correct thing by now taking it to dealer who has a better knowledge base of the systems on ZS EV.
Are you 100% sure that your car HAS received the BMS update ???.
When you carry out a full charge and balance, what is your predicted range on the GOM and what is the reported voltage on the HV pack ?.
Remember, only carry out these checks when you have reset both trips FIRST and that you boot up the car into the default mode of NORMAL / Regen level 3 with your foot clear of the footbrake and ensure you DON'T have any 12 volt items running at the time.
Especially the HVAC system !!!!!!!!.
If you have received the BMS update applied correctly, you should be seeing a predicted range on the GOM of 163 miles ( depending on the age of your car and the current distance covered on the odometer ) and a pack voltage between 448 - 450 volts.
OBTW - It is completely normal for the long term trip to predict the increased range, if it is not reset regularly, after receiving the BMS update.
For what its worth, the new face lift model is the same.
It predicts / estimates your range based on historical data collected prior to resetting the long term trip.
If you have driving a while without resetting it, driving carefully and in good weather conditions etc with no HVAC running.
Your trip will be based on achieving that predicted range.
If then you take on a longer trip ( without resetting the trips ) and the weather has changed and you are using the heater and travelling at higher speed, then the car will re-evaluate its previous prediction and then expect the previously estimated range to drop quickly.
Resetting the trips is always a safer option if taking on a new unknown trip.
