BMS (Battery Management System) updates
This page has been updated several times since March 17th, 18th, 28th, 31st and 8th April.
THIS INFORMATION IS VERY IMPORTANT FOR MGZSEV OWNERS WHO PURCHASED THEIR CAR BETWEEN OCTOBER 2020 AND JANUARY 2021. (Possibly later as we do not know how long it takes cars to reach the UK once they have left China with the faulty update already loaded.) THIS COULD ALSO AFFECT CARS PURCHASED APPROXIMATELY A YEAR EARLIER AND THEREFORE DUE A FIRST SERVICE DURING THIS PERIOD, OR THOSE WHO WERE GIVEN THE FAULTY UPDATE BY AN EFFICIENT DEALER BEFORE THE ISSUE BECAME GENERAL KNOWLEDGE.
We have been in communication with MG about the BMS update situation and it has caused major problems for quite a few drivers - as of 26th March 2021, there are still hundreds of cars affected - with some dealers having over 120 cars yet to be fixed. If the cars are leased, the dealers may be unaware of end customer's details, and therefore will have difficulty contacting them. There could have been around 2,000 cars affected.
The October BMS update (1016620R040) was faulty and led to slow equalisation charging, lower range and increased battery drain. They have confirmed several times that if owners' cars are on the VIN list (compiled by MG) of those who have had the faulty update installed in error between late October and mid January, there should be ZERO charge to install the latest fix version. The January BMS update (1230621A01 followed by a new part number ending in EU) issued end January 2021 has solved the problem - but your battery will require MULTIPLE CHARGES AND DISCHARGES to return to top condition. (We understand this could be up to approximately 30 equalisation charges.) Contact your dealer to have the newest BMS update installed. (If possible make sure you confirm your concerns in writing, as well as verbally.) If your car was affected, you will also be offered a free service. See posts below for useful information and advice. Please note: some dealers have been told to carry out the outstanding updates by 31/3. If they do it after this date they will not be reimbursed by MG. We are aware of the fact that potentially between 1,000 and 2,000 cars are still affected. (Update 31/3 - owing to the fact that so many cars are still outstanding, MG are likely to have to change their target date re reimbursing dealers.) If you dealer has not contacted you and you are concerned, get in touch with them asap. (If your car's voltage when fully charged is reading 449 - 455v, do not worry, your car is fine and does not need attention.)
If you are a very new purchaser (since January 2021), check with your dealer whether the newest BMS update is installed before you take delivery. Please note: having the faulty BMS installed does not qualify the car for rejection as it is totally fixable - although a major nuisance for some of the owners who have been affected.
Comment from Miles Roberts (Chorley - recommended dealer) 11/2/21
BMS voltages
MG has made some adjustments to the ZS EV battery pack voltage limits to increase pack longevity, but maintain the range. This is part of the new January BMS update. The new maximum voltage will be around 449/450V (assuming no loads on like climate etc). The minimum voltages have been adjusted to keep the range equal. This may also allow the car to have better regeneration from 100% charge. After the BMS update it is worth resetting both the trip meters to zero and the range will be recovered back to full capacity reading. Owners will no longer see the previous low range numbers.
Click here for a useful video on YouTube - Stuart Wright talking to Miles about BMS update issue. The relevant BMS part starts just after 25 minutes in to the 51 minute interview.
Helpful advice from Chris Wiggins (experienced EV driver and ZSEV owner) 10/2/21
BMS Balancing - ZSEV (Not MG5 issue)
This is specifically written to hopefully answer some questions about balance charging regarding those of us who had the dodgy version of software deployed to only the ZS EV between 24th Oct and early Jan, and much of the stuff in here only relates to those people when they have the fixed version on their cars, but might be of general interest to others.
Some of the info is about balance charging generally, other is based on what I have deduced using OVMS, which gives a more in depth report back on the battery, than is available otherwise. I can see the voltage of the lowest and highest cells in each pack, plus the overall battery voltage with greater accuracy. Some may be conjecture, but I’ll try to be clear about what I am confident about, what I am suggesting based on the evidence, and what I am guessing at.
What is balance charging and why do I need it?
All electric cars from all companies need balance charging. The ZS car battery is made up of 100's of cells (108 across 9 banks in the MG if I recall correctly), each individual cell (think of a cell as an individual household AA battery) holds a charge of around 4.2v when fully charged. When you charge or use a car, power is taken from the cells. In an ideal world that happens totally uniformly across the 108 cells, but in the real world some cells charge slightly quicker some slower, some drain quicker, others slower. So you end up with a mismatch in voltage between the cells. This effect is magnified by rapid charging.
A "balance charge" happens automatically at the end of any type 2 charge. (ie granny or 7kw home /destination charger). If a battery is in good health, it might be an hour or 2 of essentially shuffling little bits of power between cells to balance them all out. When the MG logo is lit solidly rather than pulsing on and off, it is balancing.
What appeared to happen with the faulty version is that process wasn’t working correctly, and cells were becoming more out of balance with each other – the car recognises this and when it is bad enough tells you with a message on the dash to say “Please slow charge”. This message will continue to pop up occasionally after the fix has been applied until you are back to normal, as it’s a separate bit of code that essentially looks and sees imbalance, and then informs you.
The side effect is when you charge to “full” some of the cells will be full, some will be slightly empty and some will be more empty. This leads to less power in the overall battery, (and therefore the lower voltage we can see). The fix version has multiple tasks it needs to achieve, it needs to try to balance all the "out of balance" cells, plus deal with the natural new day to day forces trying to further unbalance the cells, plus it is wanting to balance the banks between each other.
Charging fills the battery until cells say they are full, and then starts the micro shuffling of power. This takes a while, and it has a finite amount of time to achieve it. This is for two reasons. Both because it is capped at about 11 hours after the charging finishes, and also because people get in and want to drive the car in the morning. So for example, if your charge window is from midnight, it might finish filling the car by 4am, if you drive at 8am, it only has a 4 hour window to balance, this is normally plenty of time, but with the added issue of catching itself up means it takes more charge occasions to do it.
The indicated range is not a good indication of success or failure of the balance, it is being messed around by the inconsistent battery, plus temperature and a host of other factors so is not useful in any diagnosis around this.
What I have learned
Your first charge after the fix, will likely give you, in percentage terms, the biggest one day increase. That’s the low hanging fruit and it is likely to be smaller bites after that. Using the balance, unplug, replug and re-balance approach, it will try to spend another hour or so balancing, the measured effect is miniscule on the battery, and in my view it isn’t significantly beneficial.
I haven’t yet got enough data to back this next statement up, but my belief is a deeper discharge and recharge will result in a greater improvement than discharging to say 80% and recharging. But as I said, I can't prove that with evidence yet, so I might be wrong.
The way that a 11 hour balance shuffles things around and moves the highest cells downward slightly, and the lowest cells upward, does sometimes mean you see zero improvement in voltage at the end. However, I can see in the OVMS data that it's still been successfully balancing, and narrowing that gap between good and bad cells, resulting in typically every other night or perhaps 1 night in 3, the voltage will improve. The voltage (whilst its all you can really go on without OVMS) isn’t actually a good measure of balance but it is a symptom of where your battery is.
I haven’t yet proven this, but it shouldn’t matter if you balance with a 3kw granny or a 7kw home charge point as the balance happens at a much much lower current at the end. The only difference might be the actual charge time will take longer on the granny, so if you are driving away early the next morning, the balance time will be less. Charging for 4 hours and only allowing 4 hours to balance will help, but much of the significantly beneficial balancing happens in the latter stages.
The longer you can leave the car charging (and therefore balancing after charging) the better. I know it sometimes seems fruitless, but I can see clear improvements in the underlying data even on days that the overall voltage doesn’t improve.
My conclusion
Yes (for my car at least) I think the new version has fixed the problem, and yes it will also take a while, and multiple equalisation charges to fully fix the battery.
THIS INFORMATION IS VERY IMPORTANT FOR MGZSEV OWNERS WHO PURCHASED THEIR CAR BETWEEN OCTOBER 2020 AND JANUARY 2021. (Possibly later as we do not know how long it takes cars to reach the UK once they have left China with the faulty update already loaded.) THIS COULD ALSO AFFECT CARS PURCHASED APPROXIMATELY A YEAR EARLIER AND THEREFORE DUE A FIRST SERVICE DURING THIS PERIOD, OR THOSE WHO WERE GIVEN THE FAULTY UPDATE BY AN EFFICIENT DEALER BEFORE THE ISSUE BECAME GENERAL KNOWLEDGE.
We have been in communication with MG about the BMS update situation and it has caused major problems for quite a few drivers - as of 26th March 2021, there are still hundreds of cars affected - with some dealers having over 120 cars yet to be fixed. If the cars are leased, the dealers may be unaware of end customer's details, and therefore will have difficulty contacting them. There could have been around 2,000 cars affected.
The October BMS update (1016620R040) was faulty and led to slow equalisation charging, lower range and increased battery drain. They have confirmed several times that if owners' cars are on the VIN list (compiled by MG) of those who have had the faulty update installed in error between late October and mid January, there should be ZERO charge to install the latest fix version. The January BMS update (1230621A01 followed by a new part number ending in EU) issued end January 2021 has solved the problem - but your battery will require MULTIPLE CHARGES AND DISCHARGES to return to top condition. (We understand this could be up to approximately 30 equalisation charges.) Contact your dealer to have the newest BMS update installed. (If possible make sure you confirm your concerns in writing, as well as verbally.) If your car was affected, you will also be offered a free service. See posts below for useful information and advice. Please note: some dealers have been told to carry out the outstanding updates by 31/3. If they do it after this date they will not be reimbursed by MG. We are aware of the fact that potentially between 1,000 and 2,000 cars are still affected. (Update 31/3 - owing to the fact that so many cars are still outstanding, MG are likely to have to change their target date re reimbursing dealers.) If you dealer has not contacted you and you are concerned, get in touch with them asap. (If your car's voltage when fully charged is reading 449 - 455v, do not worry, your car is fine and does not need attention.)
If you are a very new purchaser (since January 2021), check with your dealer whether the newest BMS update is installed before you take delivery. Please note: having the faulty BMS installed does not qualify the car for rejection as it is totally fixable - although a major nuisance for some of the owners who have been affected.
Comment from Miles Roberts (Chorley - recommended dealer) 11/2/21
BMS voltages
MG has made some adjustments to the ZS EV battery pack voltage limits to increase pack longevity, but maintain the range. This is part of the new January BMS update. The new maximum voltage will be around 449/450V (assuming no loads on like climate etc). The minimum voltages have been adjusted to keep the range equal. This may also allow the car to have better regeneration from 100% charge. After the BMS update it is worth resetting both the trip meters to zero and the range will be recovered back to full capacity reading. Owners will no longer see the previous low range numbers.
Click here for a useful video on YouTube - Stuart Wright talking to Miles about BMS update issue. The relevant BMS part starts just after 25 minutes in to the 51 minute interview.
Helpful advice from Chris Wiggins (experienced EV driver and ZSEV owner) 10/2/21
BMS Balancing - ZSEV (Not MG5 issue)
This is specifically written to hopefully answer some questions about balance charging regarding those of us who had the dodgy version of software deployed to only the ZS EV between 24th Oct and early Jan, and much of the stuff in here only relates to those people when they have the fixed version on their cars, but might be of general interest to others.
Some of the info is about balance charging generally, other is based on what I have deduced using OVMS, which gives a more in depth report back on the battery, than is available otherwise. I can see the voltage of the lowest and highest cells in each pack, plus the overall battery voltage with greater accuracy. Some may be conjecture, but I’ll try to be clear about what I am confident about, what I am suggesting based on the evidence, and what I am guessing at.
What is balance charging and why do I need it?
All electric cars from all companies need balance charging. The ZS car battery is made up of 100's of cells (108 across 9 banks in the MG if I recall correctly), each individual cell (think of a cell as an individual household AA battery) holds a charge of around 4.2v when fully charged. When you charge or use a car, power is taken from the cells. In an ideal world that happens totally uniformly across the 108 cells, but in the real world some cells charge slightly quicker some slower, some drain quicker, others slower. So you end up with a mismatch in voltage between the cells. This effect is magnified by rapid charging.
A "balance charge" happens automatically at the end of any type 2 charge. (ie granny or 7kw home /destination charger). If a battery is in good health, it might be an hour or 2 of essentially shuffling little bits of power between cells to balance them all out. When the MG logo is lit solidly rather than pulsing on and off, it is balancing.
What appeared to happen with the faulty version is that process wasn’t working correctly, and cells were becoming more out of balance with each other – the car recognises this and when it is bad enough tells you with a message on the dash to say “Please slow charge”. This message will continue to pop up occasionally after the fix has been applied until you are back to normal, as it’s a separate bit of code that essentially looks and sees imbalance, and then informs you.
The side effect is when you charge to “full” some of the cells will be full, some will be slightly empty and some will be more empty. This leads to less power in the overall battery, (and therefore the lower voltage we can see). The fix version has multiple tasks it needs to achieve, it needs to try to balance all the "out of balance" cells, plus deal with the natural new day to day forces trying to further unbalance the cells, plus it is wanting to balance the banks between each other.
Charging fills the battery until cells say they are full, and then starts the micro shuffling of power. This takes a while, and it has a finite amount of time to achieve it. This is for two reasons. Both because it is capped at about 11 hours after the charging finishes, and also because people get in and want to drive the car in the morning. So for example, if your charge window is from midnight, it might finish filling the car by 4am, if you drive at 8am, it only has a 4 hour window to balance, this is normally plenty of time, but with the added issue of catching itself up means it takes more charge occasions to do it.
The indicated range is not a good indication of success or failure of the balance, it is being messed around by the inconsistent battery, plus temperature and a host of other factors so is not useful in any diagnosis around this.
What I have learned
Your first charge after the fix, will likely give you, in percentage terms, the biggest one day increase. That’s the low hanging fruit and it is likely to be smaller bites after that. Using the balance, unplug, replug and re-balance approach, it will try to spend another hour or so balancing, the measured effect is miniscule on the battery, and in my view it isn’t significantly beneficial.
I haven’t yet got enough data to back this next statement up, but my belief is a deeper discharge and recharge will result in a greater improvement than discharging to say 80% and recharging. But as I said, I can't prove that with evidence yet, so I might be wrong.
The way that a 11 hour balance shuffles things around and moves the highest cells downward slightly, and the lowest cells upward, does sometimes mean you see zero improvement in voltage at the end. However, I can see in the OVMS data that it's still been successfully balancing, and narrowing that gap between good and bad cells, resulting in typically every other night or perhaps 1 night in 3, the voltage will improve. The voltage (whilst its all you can really go on without OVMS) isn’t actually a good measure of balance but it is a symptom of where your battery is.
I haven’t yet proven this, but it shouldn’t matter if you balance with a 3kw granny or a 7kw home charge point as the balance happens at a much much lower current at the end. The only difference might be the actual charge time will take longer on the granny, so if you are driving away early the next morning, the balance time will be less. Charging for 4 hours and only allowing 4 hours to balance will help, but much of the significantly beneficial balancing happens in the latter stages.
The longer you can leave the car charging (and therefore balancing after charging) the better. I know it sometimes seems fruitless, but I can see clear improvements in the underlying data even on days that the overall voltage doesn’t improve.
My conclusion
Yes (for my car at least) I think the new version has fixed the problem, and yes it will also take a while, and multiple equalisation charges to fully fix the battery.
Comfort 2 update - info from MG website
( NB - if you purchased your car after mid June 2020, the car should have had the Comfort 2 update installed and therefore bongs etc dealt with. If you are being asked to pay for this update in 2021 as a new purchaser, you should definitely query this.)
During the lifespan of a vehicle model, various changes can be made to interior trim, exterior cosmetics or system functions to ensure that it features cutting edge technology and remains attractive to potential buyers. MG ZS EV models manufactured after mid-June 2020, will have a newly developed 2nd generation of Comfort System Operation installed on the car. This is now available for customers who wish to benefit from these later updates on earlier build models.
Whilst all the below features involve software changes to key components on your vehicle, the updated software is not available to cars with 1st Generation software as a ‘warranty upgrade’. MG’s warranty is there to cover the cost of repair or replacement of a failed part due to a manufacturing defect, and not for updates/upgrades, and will therefore be chargeable. Please speak to your MG dealer to find out associated charges for this update.
This new 2nd generation of Comfort System Operation includes changes to:
During the lifespan of a vehicle model, various changes can be made to interior trim, exterior cosmetics or system functions to ensure that it features cutting edge technology and remains attractive to potential buyers. MG ZS EV models manufactured after mid-June 2020, will have a newly developed 2nd generation of Comfort System Operation installed on the car. This is now available for customers who wish to benefit from these later updates on earlier build models.
Whilst all the below features involve software changes to key components on your vehicle, the updated software is not available to cars with 1st Generation software as a ‘warranty upgrade’. MG’s warranty is there to cover the cost of repair or replacement of a failed part due to a manufacturing defect, and not for updates/upgrades, and will therefore be chargeable. Please speak to your MG dealer to find out associated charges for this update.
This new 2nd generation of Comfort System Operation includes changes to:
- Faster system self-check when powering ‘ON’
- Infotainment volume maintains and restarts at previous volume setting after powering ON/OFF
- Auto High Beam system disable option available in menu settings
- General warning chime quality improvements and reduced volume
- Warning chimes reduced for MG Pilot and Key Reminder
- Vehicle temperature and temperature alarm featured in the instrument display
- Vehicle range always on display in instrument pack
- Vehicle can be unlocked during A/C charging, when re-locked charging automatically resumes
Battery Heater Update
This is not recommended for use in the UK - it does not get cold enough.