Everything you need to know about BMS & voltage balancing

[JodyS21]

Why after 2 BMS updates HVCC update will my car still not do a delayed charge from Smart charger, my Dealer appears to be at a loss. The other strange aspect is after the latest update my car has started to do a balancing charge as soon as I unlock the car it disengages the lock for charger cable then immediately re locks it and starts to charge, even after having been on charge all night. It will do this approx 3 times for about 20min each time before it decides it’s done. The car seems to have a mind of its own.

It may well be worth investing in a 10 quid obd2 dongle, then you'll be able to pull off the software versions that you have and compare them to other people.

 

[JodyS21]

In reply to Micky & JodyS21. My update was done on the Feb 25th and the garage is insistent that I have the latest BMS software. My third charge using the Granny Charger still give 450v and it seems a small improvement in range, however this is subjective.

Ah, 25th Feb probably means you have the 'ultra new BMS'!
We assume so far that means 450V maximum.

 

[Mark Holmes]

456 volts.

Interesting that your SOH is 99.7%, so far all I’ve seen have been 100%

 

[Cocijo]

Look at the range though!

 

[Gomev]

@Stuart Wright
I think there's a very important new development hopefully Miles can shed some light on - There's another new version of the BMS that has just appeared in the last week or 2!!!

Hi, just watched the video, very useful thank you, but no mention of this very important new development., unless I completely missed it. Do you have any updates?

 

[Mark Holmes]

Look at the range though!

Display and actual range are very different..

 

[Cocijo]

Yes of course. I’ve never seen close to this sort predicted range in N though - have you?

 

[Tim Green]

I do like the car and a lot of the software is pretty good. Eg the engine control, general driver info etc. However, many items are not properly finished off: viz the heater control and display and the satnav touch control, both of which are dire and could be sorted out with a few hours development. That is just sloppy, as is releasing firmware that is not properly tested.

On the BMS, I only use the granny charger and occasional use of fast chargers and find all that works fine for my purposes.

 

[Cocijo]

The hvac and infotainment are weak spots in the car. CarPlay I find works well - pity it won’t work the hvac too!

 

[JohnG]

Have posted in the other threads about latest BMS update. Car was collected from the dealer on Thursday and max voltage showed 449v but range in ECO with heater off was 285km (178miles) never seen such a high value before. BMS version is 0210622EU1 balancing took 4 hours and added 1kW prior to the update balancing added approx. 2.2kW Cell imbalance is now down to 22mv from 189mv

 

[AndyNWuk]

Later today, @MilesperkWh and I are making a video to explain what BMS is and to address the concerns of ZS EV owners regarding potentially unbalanced batteries.
I will ask Miles a series of questions to answer, the purpose being to create a definitive video on the subject which addresses all the questions and concerns that people might have.
This is the list of questions:

1. What does BMS stand for?
2. What is BMS generally and why is it important?
3. Can MG ZS EV owners see the battery health?
4. What should the voltage display read?
5. What if the voltage display reads something else?
6. What is battery balancing?
7. Why have some ZS EV owners got an imbalanced battery?
8. How can a ZS EV owner identify whether their car has the particular software version?
9. What impact will an imbalanced battery have?
10. Will having an imbalanced battery damage the battery or car?
11. What should an owner who believes they have an imbalanced battery do?
12. What is the procedure for re-balancing the ZS EV battery?
13. Why does balancing a battery take so long? Is there any way to speed it up?
14. Do MG5 owners need to rebalance their battery?

Can you suggest any questions to be added to this list?
Please reply. Thanks

Hi Stuart, attached are a couple of photos showing the 449 volts straight after charging.

I had a BMS Update applied by Chorley MG in Burnley on the 17th February 2021, which is claimed to be the latest version, but not sure if this has been superseded once again reading the comments on here.

I have now completed four charges since the update straight through to completion and battery balancing, the final part from showing 100% complete took another 4 to 5 hours each time.

My battery voltage as you can see from the photo's is now showing 449 volts and range on Economy Mode = 179 miles or Normal Mode = 163 miles without any heating etc.

The charging outside temperature was 3 degrees C.

Andy (Blackpool)

 

[JohnG]

Later today, @MilesperkWh and I are making a video to explain what BMS is and to address the concerns of ZS EV owners regarding potentially unbalanced batteries.
I will ask Miles a series of questions to answer, the purpose being to create a definitive video on the subject which addresses all the questions and concerns that people might have.
This is the list of questions:

1. What does BMS stand for?
2. What is BMS generally and why is it important?
3. Can MG ZS EV owners see the battery health?
4. What should the voltage display read?
5. What if the voltage display reads something else?
6. What is battery balancing?
7. Why have some ZS EV owners got an imbalanced battery?
8. How can a ZS EV owner identify whether their car has the particular software version?
9. What impact will an imbalanced battery have?
10. Will having an imbalanced battery damage the battery or car?
11. What should an owner who believes they have an imbalanced battery do?
12. What is the procedure for re-balancing the ZS EV battery?
13. Why does balancing a battery take so long? Is there any way to speed it up?
14. Do MG5 owners need to rebalance their battery?

Can you suggest any questions to be added to this list?
Please reply. Thanks

Stuart/Miles, question about "Best Practice" to speed up balancing. As you know our dealer did the heavy lifting to balance to what they were told was an acceptable level before the car could be released. So the larger the imbalance the longer it takes. Dealer had one person doing this and I believe thye had the cars in a sports hall. Routine they followed was to charge the car to 100% then switch on the ignition and then let the SOC% sink to around 93% and then charge again.

 

[Stuart Wright]

Stuart/Miles, question about "Best Practice" to speed up balancing. As you know our dealer did the heavy lifting to balance to what they were told was an acceptable level before the car could be released. So the larger the imbalance the longer it takes. Dealer had one person doing this and I believe thye had the cars in a sports hall. Routine they followed was to charge the car to 100% then switch on the ignition and then let the SOC% sink to around 93% and then charge again.

What's the question, John?

 

[JohnG]

Whats the reccomended way to carry out rebalancing as quickly as possible after the latest BMS update has been installed?

 

[Stuart Wright]

Whats the reccomended way to carry out rebalancing as quickly as possible after the latest BMS update has been installed?

We cover that in the video, John.

 

[Lovemyev]

Please correct me if I am wrong, but I am sure Miles suggested to charge to 100% and let the car balance the pack.
Then, run down the range on the GOM by either driving the car or running the heater, until the first white bar on the GOM disappears.
Reconnect the car to either a 7.0 kw wall box or a "Granny" unit and allow the car to charge and balance the pack once again.
This maybe the quickest way to accelerate the process.
I have a question :- How long is it now reasonably expected, for the balancing cycle to take after the latest update ?.
Like John, I am witnessing about 3.5 hours just to balance.
Will this balance cycle time reduce in length in the future as the pack improves ?.
One to two hours MAX feels more like the time it should take on the ZS EV given HV battery size, when in good condition - what do you folks think ?.
Miles suggested that the IPace had taken just over 2 hour to perform a full balance of the pack.
Which sounds fair considering the larger pack size on the Jag.

 

[JodyS21]

Please correct me if I am wrong, but I am sure Miles suggested to charge to 100% and let the car balance the pack.
Then, run down the range on the GOM by either driving the car or running the heater, until the first white bar on the GOM disappears.
Reconnect the car to either a 7.0 kw wall box or a "Granny" unit and allow the car to charge and balance the pack once again.
This maybe the quickest way to accelerate the process.
I have a question :- How long is it now reasonably expected, for the balancing cycle to take after the latest update ?.
Like John, I am witnessing about 3.5 hours just to balance.
Will this balance cycle time reduce in length in the future as the pack improves ?.
One to two hours MAX feels more like the time it should take on the ZS EV given HV battery size, when in good condition - what do you folks think ?.
Miles suggested that the IPace had taken just over 2 hour to perform a full balance of the pack.
Which sounds fair considering the larger pack size on the Jag.

Mines only ever had the 450V BMS on it and always been recharged (usually to full) using granny charger, done 1400miles over the last 5 weeks.
As I've not got a "smart" charger yet I've not got data, but I don't believe my car is doing much balancing at all after the charge.
On a couple of occasions, after we've plugged in, the display says e.g. 15:00 hours to charge, I've looked at the car just after it's been that amount of time to see no pulsing or lit MG badge.
- I could put one of my little cameras facing the MG badge actually and look back afterwards how long the badge is on balance for...

 

[Lambo51]

Please correct me if I am wrong, but I am sure Miles suggested to charge to 100% and let the car balance the pack.
Then, run down the range on the GOM by either driving the car or running the heater, until the first white bar on the GOM disappears.
Reconnect the car to either a 7.0 kw wall box or a "Granny" unit and allow the car to charge and balance the pack once again.
This maybe the quickest way to accelerate the process.
I have a question :- How long is it now reasonably expected, for the balancing cycle to take after the latest update ?.
Like John, I am witnessing about 3.5 hours just to balance.
Will this balance cycle time reduce in length in the future as the pack improves ?.
One to two hours MAX feels more like the time it should take on the ZS EV given HV battery size, when in good condition - what do you folks think ?.
Miles suggested that the IPace had taken just over 2 hour to perform a full balance of the pack.
Which sounds fair considering the larger pack size on the Jag.

Yes just watched podcast . Well done Miles /Stu.2 hours generally for normal re-Balance

 

[Orcadian]

My apologies but I seem to have missed something here. I got my ZS EV in October 2010 and due to COVID-19 restrictions have just turned 1000 miles. All this talk of dodgy BMS updates has got me worried. How do I know if I have this dodgy update?

 

[AndyNWuk]

Hi Orcadian,

All explained in this new Podcast Video just recorded by Stuart Wright interviewing Miles Roberts from Chorley MG

MG EVs special podcast: All your MZ ZS EV BMS Bug Frequently Asked Questions ANSWERED

In the latter part of 2020, some MG ZS EVs had a software version installed which contained a bug which caused the batteries to become imbalanced. In this interview, Miles Roberts will answer the questions that the MG EVs community have about this software update. 00:00:00 - Introduction...

www.mgevs.com

Andy (Blackpool)