Battery Equalisation/Balancing MGS5 second attempt

[Data]

Yes, indeed it is very confusing as so many people disagree on how to do the equalisation charge. I will say that Octopus & MG did both tell me to turn off smart charging before doing an equalisation charge, my dealer to. As soon as I did my car started equalising correctly. It will now equalise at any soc whereas previously it would not. Just spoken to my installer & he too has confirmed (again) I must turn off smart charging. And as I suspected, it's down to the configuration of the wall box & car. If the wall box is listed as the primary device with smart charging activated, the BMS can't control the equalisation. It seems it's that simple. And this in part actually explains why so many of us have conflicting views on the subject. Anyway, I can & have been equalising ok. No issues. And today it seems we've learned something else. All good.

 

[LenEV2016]

Yes, indeed it is very confusing as so many people disagree on how to do the equalisation charge. I will say that Octopus & MG did both tell me to turn off smart charging before doing an equalisation charge, my dealer to. As soon as I did my car started equalising correctly. It will now equalise at any soc whereas previously it would not. Just spoken to my installer & he too has confirmed (again) I must turn off smart charging. And as I suspected, it's down to the configuration of the wall box & car. If the wall box is listed as the primary device with smart charging activated, the BMS can't control the equalisation. It seems it's that simple. And this in part actually explains why so many of us have conflicting views on the subject. Anyway, I can & have been equalising ok. No issues. And today it seems we've learned something else. All good.

If I really want to make sure it's done I charge to 100% over night then the next morning hook up the granny charger, it hardly draws any power, so not using loads of power

 

[MickeySw]

Does equalisation charge have to be done from a low percentage SOC?

The short answer is no, after 100% SoC is reached (AC charging only) the BMS checks if there is a voltage difference between the individual cells and (only if there is) starts the balancing process.

Starting @ low SoC is done for a different reason altogether (calibrating the BMS).

The video below explains the principle quite nicely although some specifics do not apply to MG models

 

[Data]

If I really want to make sure it's done I charge to 100% over night then the next morning hook up the granny charger, it hardly draws any power, so not using loads of power

The only issue with doing that is that a full equalisation & balance needs to be uninterrupted & done from a low state of charge (below low battery warning) continuously up to 100% & then letting the BMS do it's thing to equalise. Again it was MG that said to me the charge must not be interrupted. Apparently if interrupted the BMS becomes disengaged from the process. What you may be seeing after plugging in your granny is just an initial minor charge which only continues for a few moments or a minute or two which almost certainly won't be a balance/equalisation. It would be interesting to analyse that more closely.

 

[LenEV2016]

The only issue with doing that is that a full equalisation & balance needs to be uninterrupted & done from a low state of charge (below low battery warning) continuously up to 100% & then letting the BMS do it's thing to equalise. Again it was MG that said to me the charge must not be interrupted. Apparently if interrupted the BMS becomes disengaged from the process. What you may be seeing after plugging in your granny is just an initial minor charge which only continues for a few moments or a minute or two which almost certainly won't be a balance/equalisation. It would be interesting to analyse that more closely.

These batteries are not that fragile and owners are unlikely to see major issues with them in their ownership.
People charge there NMC batteries to 100% everyday and see no issues.

LFP batteries like a low state of charge to 100% charge every month, less important for nmc

 

[Data]

These batteries are not that fragile and owners are unlikely to see major issues with them in their ownership.
People charge there NMC batteries to 100% everyday and see no issues.

LFP batteries like a low state of charge to 100% charge every month, less important for nmc

Yes!

 

[Joningy]

If I really want to make sure it's done I charge to 100% over night then the next morning hook up the granny charger, it hardly draws any power, so not using loads of power

I think you'll find that will not properly equalize the battery cells if I read what you are doing is correct.
Equalisation needs to be carried out in the same charge (movement) if you are interrupting the charge and connecting the "granny charger" that wont work correctly.

Additionally it makes no difference on the amount of overall electricity consumed using an ordinary wall plug (granny) or a 7Kw Home EV charger (both AC chargers) the difference being in the time taken to carry out the charge.

Also for new members, an equalisation charge is ONLY performed correctly using an AC charger, it WON'T work on a DC (services area type) charger.

 

[LenEV2016]

I think you'll find that will not properly equalize the battery cells if I read what you are doing is correct.
Equalisation needs to be carried out in the same charge (movement) if you are interrupting the charge and connecting the "granny charger" that wont work correctly.

Additionally it makes no difference on the amount of overall electricity consumed using an ordinary wall plug (granny) or a 7Kw Home EV charger (both AC chargers) the difference being in the time taken to carry out the charge.

Also for new members, an equalisation charge is ONLY performed correctly using an AC charger, it WON'T work on a DC (services area type) charger.

I was talking about smart charging not being trusted to balance charge and using a granny charger to finish the job.

I have had EVs since 2018 and have never been that precious about equalisation charging and it has never had any untoward impact on any of the EVs we have owned

 

[Joningy]

I was talking about smart charging not being trusted to balance charge and using a granny charger to finish the job.

I have had EVs since 2018 and have never been that precious about equalisation charging and it has never had any untoward impact on any of the EVs we have owned

I'm not overly concerned about "smart" charging Len, I use it all the time for normal up to 80% charging.

It's fairly straightforward to achieve full equalisation using the iSmart app, but the length of charge time has to be extended by several hours to fully complete the job, hence I temporarily set it to 12 hours.
I've got the hang of it now I've played around with it a couple of times. But if like me you get the SOC down to below 10%, as is often recommended, you wont achieve equalisation in the 6 hours of cheap (in my case Octopus Intelligent Go) night rate of 6 hours, hence the temporary extra time extension to 12 hours I've found works fine.
I never once knowingly carried out an equalisation charge on my previous MG4, although I have often charged it to 100% several times for longer trips, I may well have inadvertently managed it.

I don't really get what you are doing Len! I don't understand why you would want to connect a "granny charger to finish the job" That part of your previous message confuses me, if you are disconnecting a wall charger and connecting a granny charger, unfortunately it wont work.

The cost is identical if you use a granny charger at around 2kW or a 7kW EV charger, you are using EXACTLY the same AMOUNT of electricity, and therefore EXACTLY the same cost.
As I said earlier, the ONLY difference is the time it takes!!! The COST is identical.

THE BIG BUT for anyone new to EV equalisation here is, if you disconnect the the main 7kW charger and connect the granny charger to finish, you will not achieve a satisfactory equalisation as it should be done uninterrupted on the same charger either the 7kW charger or "granny charger" left connected, presumably if using a granny charger, the BMS will determine equalisation and stop the charge.

I've gone through several laptops and phones due to battery life degradation, but EV battery management (BMS) systems are far more sophisticated than phone and laptop chargers.

Severe imbalance of an EV battery due to poor maintenance could mean → 10–20% usable capacity loss.
As my second MG EV is now mine and not leased or financed, I'm fairly keen to do everything I can to maintain it in decent order, however confusing EV cell balancing or equalisation is.

 

[LenEV2016]

I'm not overly concerned about "smart" charging Len, I use it all the time for normal up to 80% charging.

It's fairly straightforward to achieve full equalisation using the iSmart app, but the length of charge time has to be extended by several hours to fully complete the job, hence I temporarily set it to 12 hours.
I've got the hang of it now I've played around with it a couple of times. But if like me you get the SOC down to below 10%, as is often recommended, you wont achieve equalisation in the 6 hours of cheap (in my case Octopus Intelligent Go) night rate of 6 hours, hence the temporary extra time extension to 12 hours I've found works fine.
I never once knowingly carried out an equalisation charge on my previous MG4, although I have often charged it to 100% several times for longer trips, I may well have inadvertently managed it.

I don't really get what you are doing Len! I don't understand why you would want to connect a "granny charger to finish the job" That part of your previous message confuses me, if you are disconnecting a wall charger and connecting a granny charger, unfortunately it wont work.

The cost is identical if you use a granny charger at around 2kW or a 7kW EV charger, you are using EXACTLY the same AMOUNT of electricity, and therefore EXACTLY the same cost.
As I said earlier, the ONLY difference is the time it takes!!! The COST is identical.

THE BIG BUT for anyone new to EV equalisation here is, if you disconnect the the main 7kW charger and connect the granny charger to finish, you will not achieve a satisfactory equalisation as it should be done uninterrupted on the same charger either the 7Kw charger or "granny charger" left connected, presumably if using a granny charger, the BMS will determine equalisation and stop the charge.

I've gone through several laptops and phones due to battery life degradation, but EV battery management (BMS) systems are far more sophisticated than phone and laptop chargers.

Severe imbalance of an EV battery due to poor maintenance could mean → 10–20% usable capacity loss.
As my second MG EV is now mine and not leased of financed, I'm fairly keen to do everything I can to maintain it in decent order, however confusing EV cell balancing or equalisation is.

Fair enough having owned an EV for 7 years that 10 -20 loss won't happen because of no below 10%-100% equalisation charges with an NMC battery.
LFP needs that type of equalisation charge but even them with modern tech are now a lot more robust.
But whatever makes you happy, no matter how well you try to look after it it will lose capacity over time

 

[Joningy]

Fair enough having owned an EV for 7 years that 10 -20 loss won't happen because of no below 10%-100% equalisation charges with an NMC battery.
LFP needs that type of equalisation charge but even them with modern tech are now a lot more robust.
But whatever makes you happy, no matter how well you try to look after it it will lose capacity over time

Just out of interest @LenEV2016 , what EV are you currently running, your bio says "not an MG"

 

[LenEV2016]

Just out of interest @LenEV2016 , what EV are you currently running, your bio says "not an MG"

Wife has an mg4 trophy I have a Born

 

[MickeySw]

The only issue with doing that is that a full equalisation & balance needs to be uninterrupted & done from a low state of charge (below low battery warning) continuously up to 100% & then letting the BMS do it's thing to equalise. Again it was MG that said to me the charge must not be interrupted. Apparently if interrupted the BMS becomes disengaged from the process.

THE BIG BUT for anyone new to EV equalisation here is, if you disconnect the the main 7kW charger and connect the granny charger to finish, you will not achieve a satisfactory equalisation as it should be done uninterrupted on the same charger either the 7kW charger or "granny charger" left connected, presumably if using a granny charger, the BMS will determine equalisation and stop the charge.

Severe imbalance of an EV battery due to poor maintenance could mean → 10–20% usable capacity loss.
As my second MG EV is now mine and not leased or financed, I'm fairly keen to do everything I can to maintain it in decent order, however confusing EV cell balancing or equalisation is.

Don’t think I will be ever be able to clarify this for everyone, but I will try anyway:

• an equalisation charge and cell balancing are the same thing
• the important step for balancing is to reach 100% while AC charging, starting SoC is irrelevant
• the BMS will decide if balancing is required after car is charged to 100%
• if no balancing takes place, it’s not required
• if the BMS detects a large imbalance during 'normal' operation it will suggest balancing
• discharging cells into single digit SOC will likely create a large imbalance
• re-charging imbalanced cells from very low SoC to 100% in one go can amplify the problem
• deep discharge/charge therefore 'fixed' something that wasn't broken in the first place
• large capacity losses in modern EVs are more likely due to BMS issues, not balancing
• deep discharge/charge to 100% without interruption is a procedure used to re-calibrate the BMS

 

[Joningy]

Don’t think I will be ever be able to clarify this for everyone, but I will try anyway:

• an equalisation charge and cell balancing are the same thing
• the important step for balancing is to reach 100% while AC charging, starting SoC is irrelevant
• the BMS will decide if balancing is required after car is charged to 100%
• if no balancing takes place, it’s not required
• if the BMS detects a large imbalance during 'normal' operation it will suggest balancing
• discharging cells into single digit SOC will likely create a large imbalance
• re-charging imbalanced cells from very low SoC to 100% in one go can amplify the problem
• deep discharge/charge therefore 'fixed' something that wasn't broken in the first place
• large capacity losses in modern EVs are more likely due to BMS issues, not balancing
• deep discharge/charge to 100% without interruption is a procedure used to re-calibrate the BMS

Thank you @MickeySw , that's very interesting, another version of how it should be done!
All sounds pretty logical, it just shows the confusion regarding balancing/equalisation is pretty widespread.
I'll try it at a higher SOC next time I balance (on one leg) watching with interest, not only is it much easier for us living in deep rural Hampshire to NOT need to go into deep discharge and leaving very few miles of range, due to the possibility of needing to dash off somewhere in an emergency, it's also more economical as we aren't dipping into the expensive tariff as with the method I tried, a small point but nevertheless one of the reasons for choosing MG & an EV was to hopefully save a few quid.
Does what you are suggesting on your last bullet point mean a deep discharge should be carried out occasionally to re-calibrate the BMS, or is this unnecessary.
Thanks again for a very informative reply!

 

[MickeySw]

Does what you are suggesting on your last bullet point mean a deep discharge should be carried out occasionally to re-calibrate the BMS, or is this unnecessary.

It’s not necessary if everything checks out.

 

[Alb]

You can gain an additional insight if you scan the OBD2 port and see what the cell voltage delta actually is:

The above is from my car on the 6th of November and it has never been equalised.