Is this SoH OK?

[Susanna]

@Data

Haha - you appear to have more confidence in my abilities than I have! However, in a bid to impress my grandchildren with my technical knowledge, but mainly to satisfy myself that my HV battery isn’t about to die prematurely, I have invested in the OBD scanner you mentioned, the ‘4’ version.

 

[Data]

I very much doubt your battery is about to die anytime soon Susanna! Glad to hear you have ordered an obd reader. You'll be good.

 

[MickeySw]

Pete, you may find a couple of complete battery balance (equalisation) charges will improve your SOH figures.

SoH is a measure of battery degradation, balancing will not improve this value. 85% seems exceptionally low for the age/usage of the car, unless it sat for months with either a fully charged or completely empty HV battery?

The first thing I would do is a HW reset (disconnect 12V minus pole for a few minutes, re-connect, turn on the car and move steering wheel to both extremes to clear the errors), it’s probably not going to change anything, but you never know.
In order for the BMU to re-calculate/correct the SoH value you need to do a calibration charge i.e. discharge below 10% SoC, then AC charge fully without interruption, followed by balancing.

Check SoH afterwards, if it has improved repeat the process every couple of days until it doesn’t change anymore.

do get slightly better range even in winter.

Yes, that’s correct, a proper balanced pack can increase range.

 

[Data]

SoH is a measure of battery degradation, balancing will not improve this value. 85% seems exceptionally low for the age/usage of the car, unless it sat for months with either a fully charged or completely empty HV battery?

The first thing I would do is a HW reset (disconnect 12V minus pole for a few minutes, re-connect, turn on the car and move steering wheel to both extremes to clear the errors), it’s probably not going to change anything, but you never know.
In order for the BMU to re-calculate/correct the SoH value you need to do a calibration charge i.e. discharge below 10% SoC, then AC charge fully without interruption, followed by balancing.

Check SoH afterwards, if it has improved repeat the process every couple of days until it doesn’t change anymore.

Yes, that’s correct, a proper balanced pack can increase range.

Yes, this is what I have advised Pete to do. On the ZS EV LR you only need to take the SOC down to just under the low battery warning before undertaking a full uninterrupted equalisation charge. This will occur at around the 20% SOC area but will vary from car to car by just a little depending on the state of battery balance/equalisation. As you will no doubt know it's best to take the SOC down by another 3 or 4% at least after receiving the low battery warning to make sure all battery cells are under the low battery warning threshold ensuring the BMS takes full control of the balance charge & recalibrates accordingly. With LFP batteries I'm told by folks on here the low battery warning is around the 10% mark. But I haven't confirmed that.

I have to respectfully disagree concerning a nil effect on the battery SOH by doing this. The effect on SOH is minimal but it's there in many cases & I & others have seen this. Interestingly while talking to a group of EV techs at Everything Electric they confirmed that a full equalisation can definitely improve the SOH on some batteries & always suggest doing this if a low SOH is being displayed. Not saying it will have this effect on all cars or by very much. Lots of variables come into play that will give variable results, battery chemistry for one & age of the battery is another. Apart from seeing several online videos from folks who have shown this to be a way of retrieving some lost battery capacity/degradation, I have witnessed an ex-colleague improve his ID4 degradation SOH by repeatedly carrying out this procedure & gaining back near 2% of his SOH. That's aside from the extra range he has brought back, near 37 miles. I would add the car had not been properly equalised for at least a year as far as he could tell. It will be interesting to see how Pete gets on with this.

 

[MickeySw]

Yes, this is what I have advised Pete to do.

Agreed, but what you described isn’t balancing:

Balancing is making sure that all cells are at the same voltage. This is usually done once charging has reached a set level (100% for most, although some models can do this at lower levels).
In general, individual cells are discharged until their voltage is equal to the lowest cell value, the larger the initial difference, the longer this process takes.

When doing a calibration charge, the BMU measures the actual energy required to bring the battery from (very) low to full SoC. It compares this actual value with the calculated one (based on a standard degradation model.) If they differ, the BMU will adjust SoH.

 

[decrep]

As MickeySw says, we are getting calibration and balancing mixed up, they are 2 separate things, balancing is for the battery calibration is so the computer knows what's going on.
So balancing may/maynot improve SOH.
Calibration should improve the accuracy of info displayed.

 

[Data]

As MickeySw says, we are getting calibration and balancing mixed up, they are 2 separate things, balancing is for the battery calibration is so the computer knows what's going on.
So balancing may/maynot improve SOH.
Calibration should improve the accuracy of info displayed.

Hi decrep, yes, we both know what the process is but to be absolutely clear for those that are not sure, a battery 'balancing' is the process of 'equalising' the charge across all the battery cells in the EV battery pack. Equalisation & balancing are one & the same thing. A BMS calibration is just that & is a consequence of a full & proper equalisation/balance charge as described in the vehicle owners manual. According to the owners manual this should be carried out once per month to maintain battery SOH & maintain long term range & accuracy. Folks tend to think of equalisation & balancing as separate different things but they are not. A full & proper equalisation/balance charge will recalibrate the BMS. So describing the two things as being somehow different is just semantics. But that's ok, it doesn't actually matter if you think about it. It's possible to balance/equalise your battery at 80% soc but that won't calibrate the BMS or fully equalise/balance the cells. So it's the SOC that you go to that determines whether a BMS calibration takes place NOT whether it's a balance or equalisation charge.

So to recap, a battery 'balance &/or 'equalisation' charge serves only to equalise the voltage between cells. A full & proper battery balance/equalisation taking the SOC down to below low battery warning will let the BMS control a charge to 100% to fully equalise/balance the cells & serves to recalibrate the BMS. That's all it is.

 

[MickeySw]

A BMS calibration is just that & is a consequence of a full & proper equalisation/balance charge as described in the vehicle owners manual. According to the owners manual this should be carried out once per month to maintain battery SOH & maintain long term range & accuracy.

I’m sorry, but you can’t call a BMS calibration a ‘full & proper equalisation/balance charge’, these are two different processes, with two different goals.

The user manual only describes that equalisation/balancing should be done once a month. Maybe you have a different version but the one I’m looking at doesn’t even mention BMS calibration?

 

[Data]

Hi Mickey, I think maybe you are misunderstanding what I've said & this may be the way I've explained it. I have already said/eluded to a battery equalisation/balance being one process & a BMS recalibration another. Doing one (an equalisation/balance) can lead to the other if done correctly ie: taking the SOC down to below the low charge warning then slow charging to 100%. Doing it that way will put the BMS in control of the final equalisation/balance. That's different to doing an equalisation/balance charge from say 40% to 80% where no full equalisation/balance will take place & no BMS recalibration will occur. You are just reducing to some extent the unequal cell voltage balance.

So that is describing the processes but your arguement is that an equalisation & a balance charge are two different things. That is not correct. Look it up.

 

[MickeySw]

So that is describing the processes but your arguement is that an equalisation & a balance charge are two different things. That is not correct. Look it up.

No, the two processes I refer to are
a) balancing/equalisation (same thing) I.e. discharging cells
b) BMS calibration/battery calibration charge (measuring energy, updating SoH)

The latter isn’t described in the user manual I’m looking at, maybe you could post a screen grab of yours?

 

[AnaloguePete]

Pete, the best way to balance the battery in your circumstances is to make sure you take the state of charge down to below the "low battery" warning. On my long range ZS this occurs at around 20% soc. But then just go down a bit more with the soc to make sure all of the battery cells drop below the low battery warning threshold. This will make sure that the cars BMS (battery management system) takes full control of the charge & balance of the battery. MG & Octopus Energy instructed me to turn off Smart Charging so that the charge will not be interrupted. A full & proper balance must be slow & uninterrupted otherwise the BMS won't control the balance part of the charge. Smart charging will usually stop the charge as soon as your supplier detects your car is at 100%. Obviously you don't want that, the charge must continue untill the BMS cuts it off, not your charger.

I've found very conflicting advice on this site concerning doing a balance charge. I've tried it all as have some others & many of us have found the only way to do it properly is doing it the way it's outlined above. Anyway, good luck with however you do it & let us all know how you get on.

Good idea. I'll try it when I've got a wall box, so that it can be charged back up in good time.

 

[AnaloguePete]

If you are granny charging then you won't be using any form of smart charging so that's good for a balance charge, if not somewhat lengthy. Good luck!

Yes, it took 7 hours or so! It ran at 2.3kW. After 7 hours, the power dropped to 2kW, Affter another 20 mins, the power dropped to 240W, then after another 10 mins it dropped to 1.8W, which I'm asuming is just the current drawn by the charger itself and that it had stopped charging.
The SoH has not changed

 

[AnaloguePete]

That SOH does sound a little low.
Do you have the standard range or the long range version ?.
What is your predicted range after a charge to 80% and both trips reset, if you don’t mind sharing ?.
I am just curious that’s all .

The nearest figures I have is an 84% charge, which gave a 103mi range. It was 3 dgs C tho!

 

[MickeySw]

Yes, it took 7 hours or so! It ran at 2.3kW.

I assume that’s a typo, otherwise you would have barely added 15kWh?

 

[Data]

I’m sorry, but you can’t call a BMS calibration a ‘full & proper equalisation/balance charge’, these are two different processes, with two different goals.

The user manual only describes that equalisation/balancing should be done once a month. Maybe you have a different version but the one I’m looking at doesn’t even mention BMS calibration?

The ZS EV manual states that the only way to do a 'full & proper' equalisation charge is to do a full slow charge to 100%. That's page 176. I felt this wasn't exactly very clear & so after clarification by MG & my dealer, I confirmed it means taking the SOC down to just below the low battery warning then completing a full & proper continuous slow charge to equalise/balance the battery cells. It will also recalibrate the BMS doing it this way. That is the only way to get it completely right & minimise battery degradation & maintain range for as long as possible. There is no other way (page 176 explains this). Any other equalisation method will not fully equalise the battery & will not recalibrate the BMS. There are other pages in the manual regarding equalisation.

They instructed me to 'turn off' smart charging so my electricity supplier does not interrupt the charge as so often happens during a charge. If the charge is interrupted the full & proper equalisation will not take place. There is one caveat to this concerning turning off smart charging to do this. Some folks are claiming they can equalise without turning off smart charging. I cannot & neither can any of my friends with EV's unless using a granny charger. Although some claim they are using a wall box smart charger. I'm looking into those claims but so far I can only think it might be that those individuals have their cars & chargers configured differently to the majority. This means perhaps their cars are the first device listed with there electricity supplier rather than the wall box charger. That may be the difference but I have been unable to verify this to date. My electricity supplier has told me to turn off smart charging when equalising & I have confirmed I must do that to equalise at anytime

Some months ago after asking on this site several times on how to do a full & proper equalisation/balance charge, & being given a massive amount of unintentional misinformation from well meaning folks I decided to investigate fully into this subject. I'm a retired auto engineer so it was easy to start debunking much of this misinformation being directed at me. Some of it from quite agitated people who actually didn't quite know what they were talking about. As an engineer I'm a stickler for getting it right. Of course, I don't always get it right but this stuff isn't rocket science.

One of the first things I did was read the manual, then contact MG support who advised me on the correct way to do it. They also told me the owners manual was not completely clear on every aspect of doing an equalisation/balance charge or how to do a full recalibration of the BMS. So they went through the whole procedure just as I've explained it above is some of my posts. I also spoke to my dealer, Tolleys of Colchester. They explained exactly how to do it also. There information concurred exactly with what MG support had instructed me to do. Yet some folks on here were not having it, getting a bit heated about some aspects without realising it can be a bit different for everyone depending on your car & your charging setup. I don't blame them for not understanding. Its partly the owners manual being not completely clear especially about taking the cars soc down to just below the low battery warning. MG stated they assumed folks would understand what a full & proper charge would mean but admitted it could be clearer.

Anyway that's all I have. I would add that some others on here followed my investigative pathway & have been told exactly the same as me by both MG UK & MG Australia & their dealers. One of two of them have posted about it on here. Crikey, long post!!

 

[MickeySw]

It’s certainly confusing that the ZS manual seems to use the term ‘equalisation charge’ also for a BMS calibration, but it is what it is, but you’re spot on explaining how it’s done properly.

What seems strange though is that MG recommends to do this (on a ZS EV) on a monthly basis? You mentioned that every 2 months wasn’t sufficient, how did you notice? How much does the SoH value change afterwards?

 

[Data]

Hi Mickey, yes it is confusing when manuals are not precise. I'm not used to that in engineering. I bought my ZS EV LR brand new last January. I cover about 6000 to 6,500 miles a year by car & about the same on my motorcycle. I did my first full equalisation charge after 6 weeks of ownership & the equalisation at 100% took just 10mins. So I decided to lengthen the time & mileage between this type of charge to 3 months. This wasn't so good taking around 35mins. SOH remained at 100%. After all it's a new battery! However, I brought the next few equalisation charges forward to a 2 month gap. This only lowered the equalisation period at 100% down to 30mins. Since then I'm equalising every 5-6 weeks & this is much better & is completing in around 10 to 12 mins. So I'm sticking to that.

I've learned the mileage you cover isn't necessarily the major factor determining how out of balance the HV battery might go. It's time factor & the sort of use the car is put to as well. Also driving style affects the balance of the battery., but you most likely know this stuff. I find it all very interesting.

 

[MickeySw]

Since then I'm equalising every 5-6 weeks & this is much better & is completing in around 10 to 12 mins. So I'm sticking to that.

Curious, how long does balancing take you if you charge to 100% from let’s say 80% or does it not happen at all?