Equalisation charge - NMC battery

[decrep]

At least for my ZS EV with NMC battery. It HAS to have that low battery warning & then have a 'FULL CHARGE' for the BMS to take full control & properly equalise the battery. Indeed, that's the only way my car will equalise. And I have tried it all ways. But it seems according to some, their earlier cars will equalise without the low battery warning. This seems to be for ZS & some MG4's.

Are you sure you're not mixing up calibration and equalisation? They are very separate things, calibration is for the GOM to work out where the state of charge is.
Certainly the LFP batteries a calibration requires a continuous charge from under 10% to 100%.
An equalisation charge can start from anywhere as long as it is left going after 100%.
But the NMC battery is probably different

 

[Data]

Are you sure you're not mixing up calibration and equalisation? They are very separate things, calibration is for the GOM to work out where the state of charge is.
Certainly the LFP batteries a calibration requires a continuous charge from under 10% to 100%.
An equalisation charge can start from anywhere as long as it is left going after 100%.
But the NMC battery is probably different

Yes indeed! My NMC battery appears different. Yes, I know the difference between equalisation & calibration. Often misinterpreted by some.

 

[Kithmo]

So, if you can only equalise at 100%, what exactly is my MG4 doing when it reaches 80% and carries on putting current in at a lower level if it's not equalising ?

 

[Data]

Y

So, if you can only equalise at 100%, what exactly is my MG4 doing when it reaches 80% and carries on putting current in at a lower level if it's not equalising ?

Not being rude but you need to read the thread.

 

[wattmatters]

So, if you can only equalise at 100%, what exactly is my MG4 doing when it reaches 80% and carries on putting current in at a lower level if it's not equalising ?

Because cars with NMC battery packs will perform an equalisation at end of charge no matter the state of charge limit. It's only LFP models which require charging to 100% for equalisation to occur.

 

[ReintjeWA]

So, if you can only equalise at 100%, what exactly is my MG4 doing when it reaches 80% and carries on putting current in at a lower level if it's not equalising ?

Your Trophy is equalising at 80%, some people in this thread confuse which car this forum is about, and talk about other models, that have no bearing on our MG4's. This thread should perhaps be split and/or moved to the general section, so (new) MG4 owners don't get confused.

 

[Joningy]

Two questions please:

1. Has it been clarified yet whether a full equalisation charge is achieved with an NMC battery at 80%? (or will that only happen at 100%?)

2. Is it possible to achieve a full equalisation charge (at either 80% or 100%) using scheduled charging - or will the charge terminate as soon as the charge gets to the specified charge level, without maintaining the charge connection so as to achieve the balancing? (Reason for this is to balance during off-peak power - in the middle of the night when I'm not able to watch the charge rate)

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.

 

[Kithmo]

Y

Not being rude but you need to read the thread.

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.

 

[Data]

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.

Yet you are not correct according to the way my car charges & many others, whether MG4 or ZS. We have MG4 owners coming into our ZS forum telling us their NMC batteries won't equalise at any level except 100% & they need to take the state of charge down to 10% or lower to trigger the BMS to carry out a full equalisation. Same on many ZS cars but the low battery warning is at 20% on the MK2 facelift ZS. But some folks don't seem to want to acknowledge this. It's not the same for everyone, that's the point even if they have NMC. Read the threads. This is why some of us had a state of confusion when asking for advice. There is a definite difference between battery types, software used & probably age of the cars which as far as I can tell is the reason for the confusion.

Right, I'm done on this subject. Thanks to everyone who has contributed in anyway whatsoever. Interesting to hear all the different views whatever they are. Hoping Mark Howard, the op hasn't minded the thread going on a bit.

 

[Martinonline]

This a toxic topic which invokes strong views on all sides. References are given but not detailed/imaged or are not applicable to the MG4.

I have assumed the MG BMS software was the same across all MG NMC cars but that would appear to be incorrect. So I shall restrict my comments to the car that I know - my 2023 MG4 Trophy.

In the MG4 manual 'Equalisation Charging' is defined as a mode where the BMS will attempt to equalise the charge of every battery cell. Thus an 'Equalisation Charge' is not defined here as being from any battery percentage level to another. In fact it implies the battery level when equalisation charging takes place is held.

The manual does state that carrying out a full slow charge is the only way for the high voltage battery to achieve the optimum equilibrium state (equalisation charge). I suspect no-one would argue that the MG4 optimum equilibrium state is not achieved that way. However the inclusion of the words 'equalisation charge' confuses because it is not clear whether they refer to the equilibrium state or the full charge.

After the manual defines Equalisation Charging the subsequent pages give indicative times for charging and to my mind that is how they should be read. The time for equalisation charging is included but referring back to the charge starting point (low battery alarm) does not mean that is the starting point for a 'full slow charge' leading to the optimum equilibrium state.

In fact, the manual states that if an equalisation charge has not been done for some time then the instrument display will show 'Please Slow-charge the Vehicle' because equalisation charging requires a slow charger. There is no mention of starting at a particular battery level but the inference a requirement to charge to 100% to achieve the optimum equilibrium state.

Enough of the manual, now to real world experience in my next post.

 

[Joningy]

Hi @Martinonline , I wonder if you've read the link posted earlier by our Australian member and re-posted by my self?

It's very informative as is generally the same for most car manufacturers, but mentions MG.

EV Battery Cell Balancing - EV World

How do I balance the charging of EV battery cells? Charge to 80% or 100%?

evworld.au

 

[Martinonline]

@Joningy, references a website covering EV Battery Cell Balancing. This is an extract:
Note that this is generic. However, it explains how you can tell that the battery is being balanced.

With my MG4, if I charge to 100% then after the car declares that level has been reached it proceeds to charge at various current levels until it decides to stop. I assume the various current level phase is whilst it is balancing.

If I charge to 80% then the car also continues to draw current at various levels in the same way as if I had set a 100% level. In addition, the car declares 'Battery balancing' at that 80% level. (I have not yet viewed the display at 100% but will try this weekend.) Others have posted images of their car showing this message

Now the car may not reach the 'optimun equilibrium state' but it shows the same characteristics of the equalisation charging at 100%.

To my mind, if it walks like a duck and quacks like a duck it is a duck and equalisation charging occurs at set battery levels other than 100% in my 2023 MG4 LR Trophy.

I hypothesise that this function applies to all 2023 MG4 LR Trophies.

Will an 2023 MG4 LR Trophy user provide counter arguments and evidence.

 

[Joningy]

@Joningy, references a website covering EV Battery Cell Balancing. This is an extract:View attachment 39675
Note that this is generic. However, it explains how you can tell that the battery is being balanced.

With my MG4, if I charge to 100% then after the car declares that level has been reached it proceeds to charge at various current levels until it decides to stop. I assume the various current level phase is whilst it is balancing.

If I charge to 80% then the car also continues to draw current at various levels in the same way as if I had set a 100% level. In addition, the car declares 'Battery balancing' at that 80% level. (I have not yet viewed the display at 100% but will try this weekend.) Others have posted images of their car showing this message

Now the car may not reach the 'optimun equilibrium state' but it shows the same characteristics of the equalisation charging at 100%.

To my mind, if it walks like a duck and quacks like a duck it is a duck and equalisation charging occurs at set battery levels other than 100% in my 2023 MG4 LR Trophy.

I hypothesise that this function applies to all 2023 MG4 LR Trophies.

Will an 2023 MG4 LR Trophy user provide counter arguments and evidence.

Haha, I have been regularly charging to 80% on my late October 2023 MG4 Trophy LR, I occasionally charge to 100% so I have to assume the car is getting an equalisation charge.on occasion

The MG4 it's going in 4 weeks, already purchased a new MGS5 Trophy being delivered in a week. The intention is to take a closer look at either the new MG IM5, or the long awaited MGS6, originally expected by now, but held back until 2026, possibly for launch the IM range.

I've picked up a few tips over the past nearly 2 years with an EV,
.

 

[Kithmo]

Yet you are not correct according to the way my car charges & many others, whether MG4 or ZS. We have MG4 owners coming into our ZS forum telling us their NMC batteries won't equalise at any level except 100% & they need to take the state of charge down to 10% or lower to trigger the BMS to carry out a full equalisation. Same on many ZS cars but the low battery warning is at 20% on the MK2 facelift ZS. But some folks don't seem to want to acknowledge this. It's not the same for everyone, that's the point even if they have NMC. Read the threads. This is why some of us had a state of confusion when asking for advice. There is a definite difference between battery types, software used & probably age of the cars which as far as I can tell is the reason for the confusion.

Right, I'm done on this subject. Thanks to everyone who has contributed in anyway whatsoever. Interesting to hear all the different views whatever they are. Hoping Mark Howard, the op hasn't minded the thread going on a bit.

If I'm not correct, then instead of quoting others, please answer the question, what is the car doing at 80% when it carries on putting current in ?

 

[Joningy]

No ideas, probably getting the charge completed at 80%, but it just maybe, but I don't think it is getting a full equalisation charge until it reaches 100% and past, but it's not in my electronics range of skills, I have to rely on other people more knowledgeable than me!

 

[wattmatters]

I have a 2023 MG4 Essence (= UK Trophy) with 64 kWh NMC battery.

Last time it was charged to 80% and allowed to complete at that set upper SOC charge limit:

I have power monitoring on all my home's power circuits, and the charge station used for the MG4 has its own circuit as shown above.

Once it reaches the upper SOC charge setting it eventually drops to low level power draw of between 50-150 W while it performs an equalisation for typically about 5 minutes give or take. If it's been a long time since it was AC charged to a set limit and I've been doing highway trips with mostly DC fast charging, then the equalisation period can be longer.

I could set the max charge SOC setting to 60%, 70%, 90% or 100% and it will do the same thing once it reaches that SOC.

 

[wattmatters]

Here's a time earlier this year when I charged to 100% overnight before a long drive. It had been 96 days since I'd done a full 100% charge.

Can see the equalisation period took about 2 hours to complete:

You can also see that the SOC meter hit 100% well before the battery was actually fully charged. The data from the SAIC system reports SOC in 0.1% increments. IOW the SOC meter needed a little recalibrating at the top end.

 

[Joningy]

Here's a time earlier this year when I charged to 100% overnight before a long drive. It had been 96 days since I'd done a full 100% charge.

Can see the equalisation period took about 2 hours to complete:

View attachment 39681

You can also see that the SOC meter hit 100% well before the battery was actually fully charged. The data from the SAIC system reports SOC in 0.1% increments. IOW the SOC meter needed a little recalibrating at the top end.

That's very interesting @wattmatters

 

[Jamesrr]

I have a 2023 MG4 Essence (= UK Trophy) with 64 kWh NMC battery.

23 MG4 Essence LR "77" (= UK ER) with the 77kWh NMC here.

Once it reaches the upper SOC charge setting it eventually drops to low level power draw of between 50-150 W while it performs an equalisation for typically about 5 minutes give or take. If it's been a long time since it was AC charged to a set limit and I've been doing highway trips with mostly DC fast charging, then the equalisation period can be longer.

I could set the max charge SOC setting to 60%, 70%, 90% or 100% and it will do the same thing once it reaches that SOC.

Exactly the same for me. You can see the trickle charging happen in both the Tesla App for my Wall Charger & the iSmart app for the car.

What I don't get is why people are getting so stressed about it. Just charge your car when you need to and once every couple of months let it charge on AC to 100% and leave it plugged in for another hour or so.

With our Elite "51" (=UK SE SR) you can't adjust the max charge down from 100% and my wife charges overnight anyway so it is fully charged in the morning (including any balancing her LFP battery needs).

 

[decrep]

I think the confusion comes from that generic site that says charge to 100%. True for LFP but not necessarily for NMC, depending on BMC and software.
It's evident from the evidence, at least with the MG4 NMC that balancing will occur at any set level

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