Equalisation charge - NMC battery

[wattmatters]

But does that still leave the question of whether balancing at 100% is better than at lower states of charge?

It is required every so often for a complete top balance. Cell capacity differences are really only evident from a full discharge/charge.

 

[decrep]

It is required every so often for a complete top balance. Cell capacity differences are really only evident from a full discharge/charge.

Maybe this is where some of the confusion is coming from.

 

[Data]

Maybe this is where some of the confusion is coming from.

I don't think so decrep. I was at a local MG EV meet a few weeks ago. There were just 6 of us consisting of 2 x ZS, 1 x MG5 & 3 x MG4's. All cars NMC except the MG5 & 1 MG4. The two LFP lads could easily equalise at 100%. One of the NMC MG4's could equalise from any soc as per what is being said by some on here. But the other guy with the MG4 was the same as us two ZS cars. He could only equalise at 100% & had to take the soc down to the low battery warning. The good news of course is that it doesn't need doing very often with NMC.

This being the case, it does show differences in how equalisation is achieved. It's not the same for everyone. So is this a fault with software on some cars, including mine? Well, my car has had a complete software upgrade to the newest for everyone of it's modules. Even before this, equalisation only took place at 100%. Since a full software upgrade, it's just the same so I do not think there is a fault. My car was brand new in January this year. Is it the same for all years or later models? I can't be sure but certainly some owners of later cars are having the same experience as me.

Does any of this matter?? I don't think so. It just means we need to acknowledge it's not the same for everyone when giving newbies advice because there is considerable confusion about how to do an equalisation charge amongst that group. I agree with Martin online that the manuals could also be clearer on this subject.

With my enquiring engineers mindset I've taken this as far as I reasonably can. I did this because I noticed several people on here reporting different equalisation experiences similar to mine. I do not agree with Martin online that this is a toxic subject. This forum is doing exactly what it should be doing...encouraging good robust debate & sharing of experiences. Trust me, I moderate on several engineering sites. In spite of my & others best efforts they are nowhere near as good as this site!
PS. This inability to equalise at any SOC may alter as the battery declines a little in health, it's been suggested by an MG tech. Will have to wait & see

It is required every so often for a complete top balance. Cell capacity differences are really only evident from a full discharge/charge.

Yes, it's better & is the only way to keep best range & best SOH.

 

[decrep]

@Data
Sounds like you know what you are doing, and not just quoting some UTube vid.
So I have to accept there are differences, which is rather weird, but we're getting used to weird with MG

 

[Jamesrr]

Yes, its better & is the only way to keep best range & best SOH.

Really?

I must admit I am very dubious about such a claim

You are asserting that the SOH of the battery after say 3 years and 60,000 KMs is dependant on how regularly you perform balance charging.

Are there any studies or even theoretical papers that support such an assertion?

You are suggesting that while going on a long distance journey my half hour charge will actually provide more range if I have previously performed regular balance charging than if I haven't.

I'm frankly sceptical in the extreme.

Please provide some evidence to convince me otherwise.

Sincerely,

James

 

[Data]

Really?

I must admit I am very dubious about such a claim

You are asserting that the SOH of the battery after say 3 years and 60,000 KMs is dependant on how regularly you perform balance charging.

Are there any studies or even theoretical papers that support such an assertion?

You are suggesting that while going on a long distance journey my half hour charge will actually provide more range if I have previously performed regular balance charging than if I haven't.

I'm frankly sceptical in the extreme.

Please provide some evidence to convince me otherwise.

Sincerely,

James

What car & what type of battery James? Why are you dubious? In case you didn't notice, I haven't made any suggestions.

 

[siteguru]

The car is an MG4 ER (77kWh NMC pack) ... he's included it to his Location info, like you did.

 

[Data]

Thanks siteguru.

 

[Martinonline]

@Data, I see you are back having previously stated you were done with this subject (#29). Makes me wonder if the ZS forum is not as interesting as this one. Perhaps you should get an MG4

By the way, you are not the only one with engineering experience. As for your enquiring mind you were given a great opportunity at you local MG meet. You make statements but don't amplify - what MG4 model could not equalise at below 100%, how did they know that, can they not set a battery level below 100%, what EVSE were they using? Did you ask them to join this site to add their experiences as it is different to many, if not most, NMC battery MG4 owners experiences on this forum?

This is critical information for those seeking MG4 information on this site.

In reply to your DM, I read the ZS manual linked from the app and it has the same words about equalisation charging as those in the MG4 manual except that it makes no mention of 'optimum equilibrium state' that is in the MG4 manual. You refer to the later pages in respect of the 20% start level but as I said in a previous post the tables are indicative charging times to 100% with no mention of being mandatory states to allow the car to equalise at 100%.

It is good that you now accept equalisation/balancing can occur at battery levels below 100% as I accept that this may not be true for all NMC MGs.

It would be good to hear from an MG4 owner with the car being unable to balance at less than 100% and/or need to start below 20%.

I think it would be beneficial that there should be no more posts as we wait for that one.

 

[Jamesrr]

Hi @Data ,

When responding to a comment re balance charging at 100%

It is required every so often for a complete top balance. Cell capacity differences are really only evident from a full discharge/charge.

You said

Yes, it's better & is the only way to keep best range & best SOH.

I expressed my scepticism re the effect on SOH.

What car & what type of battery James? Why are you dubious?

As noted an MG4 with NMC 77kWh battery.

I'm dubious because I've not seen any technical analysis that says balance charging is required to maintain the long term health of the battery.

I understand how the balance charging affects the accuracy of the BMS in determining if the system is "fully charged" and how much charge it may have remaining at any state of discharging, but you have said it will affect the actual state of health of the battery.

I'd like to understand what evidence there is for that.

In case you didn't notice, I haven't made any suggestions.

Haven't you suggested balance charging is "the only way to keep the best SOH" of the battery?

Cheers,

James

 

[Data]

@Data, I see you are back having previously stated you were done with this subject (#29). Makes me wonder if the ZS forum is not as interesting as this one. Perhaps you should get an MG4

By the way, you are not the only one with engineering experience. As for your enquiring mind you were given a great opportunity at you local MG meet. You make statements but don't amplify - what MG4 model could not equalise at below 100%, how did they know that, can they not set a battery level below 100%, what EVSE were they using? Did you ask them to join this site to add their experiences as it is different to many, if not most, NMC battery MG4 owners experiences on this forum?

This is critical information for those seeking MG4 information on this site.

In reply to your DM, I read the ZS manual linked from the app and it has the same words about equalisation charging as those in the MG4 manual except that it makes no mention of 'optimum equilibrium state' that is in the MG4 manual. You refer to the later pages in respect of the 20% start level but as I said in a previous post the tables are indicative charging times to 100% with no mention of being mandatory states to allow the car to equalise at 100%.

It is good that you now accept equalisation/balancing can occur at battery levels below 100% as I accept that this may not be true for all NMC MGs.

It would be good to hear from an MG4 owner with the car being unable to balance at less than 100% and/or need to start below 20%.

I think it would be beneficial that there should be no more posts as we wait for that one.

Actually Martin, if you read my earlier post about my meet with others, it's all explained about who could & couldn't equalise at below 100%. Read & digest! It's quite easy to understand so folks can see the facts. We discussed at some length the situation regarding these interesting facts. As for my engineering experience it is unimportant for many of the discussions we are having. And my experience all relates to ice engined vehicles, not EV's. That's why I'm here.

It's good you now accept not all cars seem to equalise in the same way regarding NMC packs.

The reason I'm still here Martin is because individuals, apparently including your goodself, don't understand or read my posts correctly or even the whole thread & go on to make inappropriate comments, assertions & remarks. It's a bit like some people seem to want to shoot the messenger. They commonly ask questions of me that have already been answered by me in earlier posts within the same thread. Many are oblivious to the context of the post they query or indeed the thread & the answers I give. If folks just read the thread properly mostly everything would be clearer for them. I do accept this is sometimes a 'thing' that happens on these forums, but....

Trust me Martin, the ZS forum is just as interesting!

Hi @Data ,

When responding to a comment re balance charging at 100%

You said

I expressed my scepticism re the effect on SOH.

As noted an MG4 with NMC 77kWh battery.

I'm dubious because I've not seen any technical analysis that says balance charging is required to maintain the long term health of the battery.

I understand how the balance charging affects the accuracy of the BMS in determining if the system is "fully charged" and how much charge it may have remaining at any state of discharging, but you have said it will affect the actual state of health of the battery.

I'd like to understand what evidence there is for that.

Haven't you suggested balance charging is "the only way to keep the best SOH" of the battery?

Cheers,

James

Hello James. There is plenty of evidence that balancing your battery on a regular basis helps protect your HV battery SOH. In you MG4 MANUAL it states that equalisation preserves range & helps maintain your battery SOH. It actually helps extend your batteries life by preventing over or under charging of cells which can of course cause damage over time if not addressed. It allows the battery to actually 'fill itself up properly'. Of course there are many things that help preserve SOH. Equalisation is just one of them. It says this in my manual also. If you know something about EV batteries & their chemistry & how they work it's also fairly easy to understand that this is the case. If you do some further research there are articles on tinternet reinforcing this. Do your own research. It's there.

 

[Jamesrr]

Hello James. There is plenty of evidence that balancing your battery on a regular basis helps protect your HV battery SOH. In you MG4 MANUAL it states that equalisation preserves range & helps maintain your battery SOH. It actually helps extend your batteries life by preventing over or under charging of cells which can of course cause damage over time if not addressed. It allows the battery to actually 'fill itself up properly'. Of course there are many things that help preserve SOH. Equalisation is just one of them. It says this in my manual also. If you know something about EV batteries & their chemistry & how they work it's also fairly easy to understand that this is the case. If you do some further research there are articles on tinternet reinforcing this. Do your own research. It's there.

Well I have done quite a bit of research both before purchasing our MG4s and since.

Balancing did not come up as a significant determinant to long term battery health.

Not regularly charging past 80% and using DC fast charging only when necessary were the main recommendations.

I got Gemini to provide a quick summary....

--------
What does the mg4 technical manual recommend to maintain battery health?

AI Overview
+5
The MG4 Technical Manual recommends using slow charging whenever possible and only using rapid charging for long trips or emergencies to preserve battery health, and it also advises against leaving the vehicle unused for too long. However, the manual's specific recommendations vary by battery type: for the 51 kWh LFP battery, it's generally fine to charge to 100% regularly, though a full charge may be needed to balance the cells, while for the 64 kWh or 77 kWh NMC batteries, it recommends limiting regular charging to 80%. For long periods of inactivity, it's best to store the vehicle with the high-voltage battery at approximately 60% charge.

General Recommendations

Use Slow Charging:
Whenever possible, use a slower charging method to maintain the high-voltage battery's service life.

Use Rapid Charging Sparingly:
Reserve rapid (DC fast) charging for long-distance journeys or emergencies, as it can cause more stress on the battery.

Recommendations by Battery Type
For the 51 kWh LFP Battery:
You can typically charge to 100% on a regular basis without significant harm to battery health.

For the 64 kWh or 77 kWh NMC Batteries:
It is recommended to limit regular charging to 80% to preserve battery health.

For Long-Term Storage
Store at ~60% Charge: If you won't be using the vehicle for an extended period, store it with the high-voltage battery at around 60% state of charge.

For Long Trips
Charge to Full (if needed):
For long trips, you can charge either battery type to 100% to ensure sufficient range.

Perform Balancing Charges:
For NMC batteries, occasionally charging to 100% (and sometimes LFP batteries too) is beneficial for balancing the battery cells and ensuring accurate state of charge readings.
----------

Balance charging is useful for accurate soc readings rather than soh on my reading.

 

[DaveIJ]

All makes sense to me thanks for this

 

[Martinonline]

@Data, I do read your posts carefully and reply as required. However I believe that you do not read others' posts and when challenged becomes defensive and tell them to read the thread.

You consistently have not provided documentary or image evidence to support your statements. Statements such a 'There is plenty of evidence' does not cut the mustard.

As regards your post about the MG Meet, all you said was that one MG4 NMC owner could 'equalise from any soc' and the other could only equalise from the low battery warning and only at 100%. No mention of whether the first person could equalise at less than 100%. According to your latest post, you 'discussed at some length the situation regarding these interesting facts'. But you deemed it unnecessary to report these discussions which, hopefully covered the questions I asked in my last post and widen the forum's knowledge base. Again another example of a failure to provide evidence and a fixation on the belief that equalisation charging can only occur at 100% battery level.

So, here are 2 direct questions:

What do you understand is happening when the BMS declares to the Infotainment screen that it is 'Battery balancing' ? Bearing in mind this has been recorded at set battery levels of 100% and lower.

Do you accept that some MG4 NMC cars can equalise (balance) charge at battery levels other than 100%?

 

[Data]

Hello Martinonline, what I said about my recent meet is LISTED BELOW. It does include I think the information you are complaining about not being there. Although I'm not sure what you mean by 'the first person' info. I suspect you are refering to the LFP MG which surely you know has to equalise at 100%. I do say who could do what & at what soc. Ok I could have listed it differently but it does give you the info that mostly matters if you read it.

My discussions at the meeting were similar to what we are having here. And yes, you are right, I deemed it unnecessary to report any additional info as there wasn't any. So nothing particularly to add to this discussion other than it confirmed yet again that there are some differences. If there had been anything extra either technical or experience wise from the other drivers that may have helped add to the discussion, trust me, it would have been mentioned here.

By the way Martin, of the 6 folks I met, only 2 of us are on here.

To add, you accuse me of several things, an example of which is - apparently I'm fixated with the belief equalisation can only happen at 100%. To clarify, I've never been fixated in that way. I have said however that a full & proper equalisation can only happen at 100% irrespective of battery type. That is an actual fact & is listed in all the MG EV manuals. It's listed in the Nissan Leaf manual, the Kia E-Niro manual, the ID3 manual. No doubt it's in all the manuals. You were saying something quite different at the time & appeared confused as to what a battery balance was. But I'm not going there again. Am I defensive? Yes when folks accuse me unjustly or try to put words in my mouth.

Regarding your two direct questions. Once again you demonstrate you haven't read the thread, or my posts in particular, or you haven't understood them. If you had you would not be asking these questions. They have already been answered in earlier posts. However to reiterate:

Q1. I think the same as you.
Q2. As I said in earlier posts in this thread & indeed in other threads, of course I fully accept some MG4's can equalise at levels of 100% or less, just the same as some ZS EV's can. I'm looking for answers as to why mine & some others do not. I'm pleased to see you have changed your mind to accept these differences.

THE MEET UP: (what I posted)
There were just 6 of us consisting of 2 x ZS, 1 x MG5 & 3 x MG4's. All cars NMC except the MG5 & 1 MG4. The two LFP lads could easily equalise at 100%. One of the NMC MG4's could equalise from any soc as per what is being said by some on here. But the other guy with the MG4 was the same as us two ZS cars. He could only equalise at 100% & had to take the soc down to the low battery warning. The good news of course is that it doesn't need doing very often with NMC.

Ok so going from this thread now. Won't be back. If you could tone down the hostility Martin that would be great. Bye for now.

 

[wattmatters]

I'm dubious because I've not seen any technical analysis that says balance charging is required to maintain the long term health of the battery.

For clarity (since I was quoted), I've made no statement about this.

As a general principle though (i.e. not MG or even car specific, this applies to any battery pack with multiple cells) ensuring cells do not get too far out of balance does matter for both useable capacity and for a pack's overall state of health.

One cell in a pack will always reach the upper charge or lower discharge voltage threshold first, it's then a matter of how far ahead of the rest of the pack that cell is. Keeping that differential to a reasonable level matters.

With well matched cells such as is typical in our cars, the impact of minor imbalances will not be noticeable but if a large enough imbalance is allowed to creep in, then it will manifest in reduced available capacity.

Allowing significant cell imbalances to go unchecked can also result in pack health issues, as one cell may be consistently exposed to higher (or lower) voltages and over time that results in uneven cell degradation. We then have a weak link in the chain.

That said, we mostly need not be concerned with our cars.

Cells are typically well matched when they manufacture a pack, and the BMS is looking after the balancing for us which will typically happen periodically in normal use.

And if not, then the car will alert us if it detects a cell equalisation charge is required.

Just allow the car to fully charge every so often and all will be good. For SOC calibration and pack health check reasons an occasional deep discharge and full recharge is also helpful.

 

[EVentropy]

Why don't one of you guys plot HV & LV cell vs time whilst charging from say 75%?
On at least a 7kW AC charger.
This will prove what YOUR car is doing with current software. It will be a biggish file and take some time; Instead of all the supposition.
I would be most grateful if I could compare outputs of same vehicle as mine but nobody seems interested to do it, so actually the data point transitions are left to a sketchy manual and internet hearsay.

eg
This for MG4 LiFePO4

Post in thread 'What to ask the HV tech if your car plotted this.......'

Wednesday at 12:16 AM

Charging from 30% to 98% then plotting trace thru balancing

I don't know why trace has skipped section to 3.65V cutoff but assume exponential curve continues
to 3.65V cuttoff.
I would be interested to see another Sr/SE/ Excite (Oceania) LiFePO4 plot for comparison as this balancing mechanism seems to be only to get high cell out of degradation zone. Lasting 6.5mins.
Is it screwing up and blowing off low cell as well. (With a higher resistance, ie flatter curve.)
That initially, is too fast for LiFePO4. (Green decay trace.) As i've watched my boat CaLB cells decay.
More...

• EVentropy

• 

 

[Joningy]

See Equalisation charge - NMC battery thread.

Above I've posted a screen shot from the MGS5 manual, which clearly shows needing to be charged to 100% to perform the equalisation charge.

still unconfirmed though is the need to reduce the battery SOC to below 30% (alarm level) before attempting the equalisation charge, but I don't think it's necessary,

But the article does state exactly as I referred to above, that if charging on an overnight cheap tariff (mine is 6 hours with Octopus @7p/kWh between 11.30pm and 05.30am) it may take one charge session to raise the charge sufficiently to allow a second (possibly next night) charge, to fully carry out the balancing act.
Or charge when closer to say 70 to 80% to achieve the full charge of 100% allowing enough time for the cars electronic system to carry out the equalisation.
EV Battery Cell Balancing - EV World
This Australian link is the most informative in layman's terms I've yet come across.
An extract says:-

"it is generally good practice to regularly charge a Lithium Nickel Manganese Cobalt battery (NMC) to only 80%, it is also equally good practice to fully charge NMC batteries to 100% (on an AC charger) at least once every few months"

NOTE FAST DC charging WILL NOT perform an equalisation charge.

The above article was posted here by @wazmac, an Ozzy forum member, it covers virtually all we need to do.

I've tried to spell it out in simple words, so non technically minded folk get a chance to understand, but apologies for any repeated words or sentences.

Let's hope this forum has gone some way in dispelling the many myths of charging correctly.

I was being sarcastic actually, I have read the thread and all the rubbish being spouted about NMC batteries not equalising at 80%, which is why asked the question, which was aimed at those saying you have to charge to 100% to equalise.

My question to MG.
NMC battery Equalization charge details.
There is much debate on the correct process. I think it is necessary to charge to 100% to achieve this. Which is I believe is correct with MG.?

MG response...
"To achieve the battery equalisation, you must run the battery down to 10-15% and charge slowly to 100%. MG recommend this is carried out by 3 pin plug, or on a 7kwh charger. As the vehicle is charging, it will show blue lights around the charging area, green when it is fully charged. When all of the lights have gone off, this confirms the battery equalisation has taken place. MG recommend this is carried out once per month"

In this case my current MG4 has seldom had the battery equalisation carried out correctly as I have only let the SOC drop below 15%, a couple of times, so those thinking charging to 80% to get a proper equalisation (which I've always considered to be incorrect) need to take another look.
My new MGS5 which I pick up next week will be treated differently, but as we live remotely in rural Hampshire, I don't like to let it run low, just in case we need to dash off on an emergency errand.

I'll relay this MG response to other forums I've responded to.

 

[Tuareg]

"As the vehicle is charging, it will show blue lights around the charging area, green when it is fully charged. When all of the lights have gone off, this confirms the battery equalisation has taken place"

Wrong.

As the vehicle is charging, it will display blue lights when preparing to charge and green lights around the charging points when charging. The charging port lights power off when charging is complete.

Best you correct your MG contact point.

 

[Martinonline]

@Joningy, thank you for getting MG involved.

I have never disputed that a proper equalisation only occurs at 100%. The discussion was about whether cell balancing (aka equalisation) occurs at battery levels below 100%. This hypothesis was based on the the infotainment screen displaying the message 'Battery balancing' and having charging characteristics associated with proper equalisation at 100%.

As you have a link to MG, perhaps you could ask a follow-up question:

What is the BMS doing to the cells of the battery when the message 'Battery balancing' is displayed on the infotainment screen?

In June I posted the filling on the General Chat forum in order to bring clarity to the subject. But this was not accepted because 'balancing' was considered as being the same as 'equalisation' and thus could not occur at less than 100%

I do not disagree with your statement about doing a full equalisation is what is recommended in the manual. And that it leads to the most accurate battery capacity and range prediction.

However in my MG4 manual the word 'calibration' never appears in relation to the HV battery only the word 'equalisation'. The word 'balancing' does not appear in the manual either but only on the infotainment display preceded by the word 'battery'.

Thus we are dealing with semantics here. I propose the following definitions:

Balancing: The BMS activity that seeks to ensure the battery groups are all at the same voltage specified by a battery percentage level.

Calibration: The BMS activity that seeks to record the battery level range and shape of discharge so as to translate that to percentage battery capacity and predicted mileage

Equalisation: The BMS activity starting from a low battery voltage level to a maximum voltage level to ensure the most accurate battery capacity and range prediction. This involves balancing and calibration. It is essential for those cars only DC charged where no balancing occurs.

Thus 'balancing' is not 'equalisation' and thus cannot give the most accurate range and battery level estimates.

Recently my concerns have been to seek references and data for the statements being made about the equalisation process. You have now provided one.