Balance Charging - a few questions

[2Sheds]

A few EV noob questions

I have had my phase 2 Trophy for about 2.5 months now, and as it is owned not leased, I am keen to keep the battery in as good a state of health as I can. With that in mind I have been cycling it between around 20-80% as per recommended practice. The thing is that we aren't doing a lot of mileage, particularly after the first couple of weeks of getting the car, and I've been waiting for a long while now for a charge cycle to fall just before a long run to do a balance charge, so the car doesn't sit around at 100%. Just isn't happening though! As a consequence I haven't yet done a balance charge ?. (It was at 100% when we picked it up though). So far the car has done about 1400 miles, been exclusively charged at home, averaging about once every ten days or so (using Ohme charger, not granny lead) with the exception of one 25% top up at a 50kW rapid. So...I have a few questions:

1) The recommendation is to perform a balance charge once a month. So is this requirement purely a time based thing, or is that just based on an average usage? In other words, is it ok to do it less often if the car is used infrequently/does light mileage?

2). Does it matter what SoC the battery starts off at when doing a balance charge, ie is it ok to do it from 80%, 60%, whatever, or should it be a from low SoC? (I think I read somewhere that the battery should be occasionally charged 10-100%). I ask this so that if we do a longer trip in-between the normal 20-80% routine, I could balance it then, eg if it was at 60%.

3). Am I overthinking this? I am worrying too much about it?!

Thanks in advance.

 

[Corindikev]

I set the limit to 60% today to see what would happen. It charged to 60% and then went in to balance mode. The iSmart app continues to say charging and the finish time is displayed as the current time. The battery display on the infotainment screen displays balancing and the input current rapidly declines. After 8 minutes the app is showing 0.0 kW charging power. I changed the target to 80% and it is now charging at 6.6kW.

 

[tsedge]

A few EV noob questions

I have had my phase 2 Trophy for about 2.5 months now, and as it is owned not leased, I am keen to keep the battery in as good a state of health as I can. With that in mind I have been cycling it between around 20-80% as per recommended practice. The thing is that we aren't doing a lot of mileage, particularly after the first couple of weeks of getting the car, and I've been waiting for a long while now for a charge cycle to fall just before a long run to do a balance charge, so the car doesn't sit around at 100%. Just isn't happening though! As a consequence I haven't yet done a balance charge ?. (It was at 100% when we picked it up though). So far the car has done about 1400 miles, been exclusively charged at home, averaging about once every ten days or so (using Ohme charger, not granny lead) with the exception of one 25% top up at a 50kW rapid. So...I have a few questions:

1) The recommendation is to perform a balance charge once a month. So is this requirement purely a time based thing, or is that just based on an average usage? In other words, is it ok to do it less often if the car is used infrequently/does light mileage?

2). Does it matter what SoC the battery starts off at when doing a balance charge, ie is it ok to do it from 80%, 60%, whatever, or should it be a from low SoC? (I think I read somewhere that the battery should be occasionally charged 10-100%). I ask this so that if we do a longer trip in-between the normal 20-80% routine, I could balance it then, eg if it was at 60%.

3). Am I overthinking this? I am worrying too much about it?!

Thanks in advance.

1) There are two things happening here: balancing the battery to equalise cell voltages across the pack and calibrating the battery voltage curve as it ages.

Balancing can occur at a ranges of voltages, including 80%. However proper calibration beeds a charge to a full 100% and this is why it is recommended monthly.

The key thing for battery longevity is not to leave the car above 80% for long periods of time (weeks or longer). So do a 100% charge before you are about to do one of your longer journeys. If going on holiday without the car, leave between 50-80%.

2) No it doesn't matter. The reason for the 10-100% every 3-6 months is again to aid calibration.

3) No, it is confusing. Happily nothing bad will happen if you don't do these things for an extended period - the worst that is likely to happen is that the car slowly loses track of the range of the battery and you may get inaccurate range predictions and the car might suddenly drop range at low states of charge as it struggles to work with an unbalanced battery of uncertain capacity.

 

[barry7153]

Thank you, that clears up a lot of my questions, however a couple remain.
1. Is there any way post charging, IE a couple of hours later, that you can check if the previous charge achieved balancing/calibration.
2. If not, does the message I am told the car displays, refer to balancing or calibration and can that be used to decide when to go to 100%.

 

[Corindikev]

Balancing can occur at a ranges of voltages, including 80%. However proper calibration beeds a charge to a full 100% and this is why it is recommended monthly.

The monthly 100% charge recommendation is not in the MG4 manual so who made this recommendation?

While the equalisation process occurs at whatever you set the maximum charge rate at the manual does say that full equalisation is the only way to ensure optimal battery SOC as per the manual extract below but nowhere is a time-frame mentioned.

Note: Carrying out a full slow charge is the only way
for the high voltage battery to reach the optimal
equilibrium state (equalisation charge).

It does say this though

If an equalisation charge has not been carried out for
sometime, the message centre in the instrument pack will
display 'Please Slow-charge the Vehicle'. Please refer to
'Slow Charging' in the 'Starting and Driving' section.

So does "sometime" mean a month of fast or rapid charging or is this just someone's interpretation of sometime? I seems to me that the car will tell you when it is needed.

 

[Tight Git]

Thank you, that clears up a lot of my questions, however a couple remain.
1. Is there any way post charging, IE a couple of hours later, that you can check if the previous charge achieved balancing/calibration.
2. If not, does the message I am told the car displays, refer to balancing or calibration and can that be used to decide when to go to 100%.

The car cannot tell you if it has completed the balance charge after it has finished but your EVSE (charger) should be able to, unless you are using a dumb one like the granny.

Attached is my Zappi report from last night when I did a charge from 4% to full - if you look at the blue line it drops from 7kW at about 03.40 and balances until 04.10 (it is just about visible but low down!)

 

[barry7153]

Cheers for that.

 

[fnegroni]

This is mine from yesterday: charging from 3% on a granny charger using a Tapo smart plug:

 

[Bam Bam]

Attempted our first balancing charge after finally getting the battery to 10%.

The Givenergy EV info doesn't seem as detailed, but you can see here that the power dropped to about 50% for a half an hour before finishing. Then there was a little 850W charge 20 minutes later, presumably part of the balancing process.

 

[tsedge]

The monthly 100% charge recommendation is not in the MG4 manual so who made this recommendation?

MG makes this recommendation.

It applies to LR cars only, the SR versions have a different battery chemistry (LFP) and there the recommendation is to always charge to 100% and to do that at least weekly, as calibration and balancing are more important for this chemistry.

This recommendation has existed since the car was launched.

The 10-100% every 3-6 months also came from MG but this surfaced more recently, I don't recall it being discussed in the first 6 months the car was on sale.

Not everything appears in the manual and there have been different versions of the manual.

 

[wattmatters]

The monthly 100% charge recommendation is not in the MG4 manual so who made this recommendation?

Frankly the manual is confusing when it comes to charging advice so it is little wonder there is conflicting advice out there.

e.g. it does recommend a monthly equalisation charge but that does not necessarily mean charging to 100%:

For LFP models this does mean charging to 100% because LFP requires a full charge to do an equalisation and is probably why LFP models don't enable setting a max SOC less than 100%.

NMC does not require 100% SOC for equalisation.

But it also says this:

• a weekly full charge if used daily, and
• a full low power charge every 3-6 months:

Shoulder shrugs all round.

MG makes this recommendation.

It applies to LR cars only, the SR versions have a different battery chemistry (LFP) and there the recommendation is to always charge to 100% and to do that at least weekly, as calibration and balancing are more important for this chemistry.

The problem is the manual, at least the one here in Australia, does not differentiate between LFP and NMC when it comes to charging advice.

Then to confuse matters more, this page implies all models need to be charged to 100% for equalisation:

In this instance battery type 1 is 51 kWh LFP, type 2 is 64 kWh NMC and type 3 is 77 kWh NMC (edit: the manual does not explicitly state this though).

 

[tsedge]

Some of the recommendations came via the MG website and others in communications from MG UK in emails to enquiries from users.

I don't have a record of exactly where each recommendation came from but I am confident these are accurate and real recommendations.

Of course, people are free to ignore them and many aren't even aware, happily it seems little bad happens if you do.

The only scenario in which damage is likely is leaving a LR car fully charged for weeks or months.

 

[fnegroni]

The problem is the manual, at least the one here in Australia, does not differentiate between LFP and NMC when it comes to charging advice.

Then to confuse matters more, this page implies all models need to be charged to 100% for equalisation:

View attachment 28366
In this instance battery type 1 is 51 kWh LFP, type 2 is 64 kWh NMC and type 3 is 77 kWh NMC (edit: the manual does not explicitly state this though).

Type 1 is 64kWh , type 2 is 51kWh.

 

[Corindikev]

I read the entire manual when I first got the car but obviously forgot the extra battery maintenance stuff in the Service & maintenance section (why isn't all this in the battery section Charging & discharging requirements) & that bit about less than 10% or 1 grid is completely confusing? What is 1 grid? There are 3 separate sections on the HV battery and charging.

Then the statement that failure to follow the guidelines will result in HV battery damage & invalidate the warranty seems like an attempt to get out of any battery warranty claim.

I think the advice provided by Euan McTurk in a number of informative videos is far better than trying to follow the stuff in the manual. That plus the reports of drivers not following any regime at all and getting enormous mileages from a NMC battery albeit over 5-8 years.

Reported on an Electric Viking video recently is that all new MG4s sold in Thailand are being given a lifetime battery warranty & that this warranty will eventually be extended to all MG 4s sold previously. An owner of a Cyberster in China reported his car came with a lifetime battery warranty. The battery is the same 64kWh battery installed in the MG Essence 64/Trophy model.

I wonder what "lifetime" means and what the list of conditions are and where the details are printed or hidden.

 

[Rolfe]

I think in principle that lifetime will mean that it won't be the battery that will cause the car to be considered at the end of its life. Maybe it will rust to bits first.

 

[wattmatters]

Type 1 is 64kwh, type 2 is 51kwh

Well there you go. Yet the manual doesn't actually tell us which is which. Silly me for thinking the type numbering would go up in order of capacity!

I read the entire manual when I first got the car but obviously forgot the extra battery maintenance stuff in the Service & maintenance section (why isn't all this in the battery section Charging & discharging requirements) & that bit about less than 10% or 1 grid is completely confusing? What is 1 grid? There are 3 separate sections on the HV battery and charging.

I agree - the information on battery use and care in the user manual is confusing and unhelpful.

My take:

• mostly charge with AC chargers (up to ~11 kW) where possible
• if regular AC charging isn't possible (unusual) then schedule one complete AC charge every so often
• occasionally charge NMC models to 100%
• don't worry about charge SOC limits with LFP models, excepting:
• don't leave the battery (either type) at a very high (>95%) or very low (<10%) state of charge for long periods
• if leaving car for long periods unattended then leave the drive battery in the 50-70% SOC range and consider using a 12 V battery tender.

 

[Ethernea]

How do you guys start the balancing of the cells?

I have a NCM battery 64kWh and this is my 2nd charge after getting this car...

I figured...this car battery is new. It hasn't been used or charged before. So maybe it needs "balancing"

So today it went from 28% to 100%... And i got to be sit here to watch what happens when it does...

And it changed from slow charging 6.4kW to trickle charging 3.9kW

And it has been in 100% for 10 minutes and it still says trickle charging at 3.9kW despite it says its 100%.

It doesn't say "battery balancing" or whatever...

Is this what balancing looks like in mg4?

Should i wait until it stops on its own - so its entirely 100% maxed out?

Or should i charge ONLY 20 to 80% and once a month up to 100% and let it stop on its own?

Its weird it says 100% and still "trickle charging" at 3.9kW for 20 minutes by now.

Says 100% and 469 km range.

 

[Coulomb]

How do you guys start the balancing of the cells?

It happens automatically when you leave the car plugged in to AC charging and it gets to 100%.

I have a NCM battery 64kWh and this is my 2nd charge after getting this car...

I figured...this car battery is new. It hasn't been used or charged before. So maybe it needs "balancing"

Yes, it likely does, after standing in car yards, on a ship, etc.

And it changed from slow charging 6.4kW to trickle charging 3.9kW

That's the first stage of balancing.

And it has been in 100% for 10 minutes and it still says trickle charging at 3.9kW despite it says its 100%.

That's the indication that it's balancing. I wish MG made it more obvious. Many users would look at that and say "oh, it's full, I can pull out the plug now".

It doesn't say "battery balancing" or whatever...

Is this what balancing looks like in mg4?

I believe so, yes.

Should i wait until it stops on its own - so its entirely 100% maxed out?

Yes, unless you really need to drive the car.

Or should i charge ONLY 20 to 80% and once a month up to 100% and let it stop on its own?

Once it's balanced, yes, charge whenever you feel like (no need o wait till it gets down to 20%), but only to 80% except once a month, or when you know you'll need the extra range.

Its weird it says 100% and still "trickle charging" at 3.9kW for 20 minutes by now.

The amount of time it spends balancing depends on many factors, basically how unbalanced the battery is. The very first balance is expected to take longer; it may even take several hours, or it might give up and try again next time you charge to 100%.

 

[Ethernea]

It happens automatically when you leave the car plugged in to AC charging and it gets to 100%.


Yes, it likely does, after standing in car yards, on a ship, etc.


That's the first stage of balancing.


That's the indication that it's balancing. I wish MG made it more obvious. Many users would look at that and say "oh, it's full, I can pull out the plug now".


I believe so, yes.

Yes, unless you really need to drive the car.

Once it's balanced, yes, charge whenever you feel like (no need o wait till it gets down to 20%), but only to 80% except once a month, or when you know you'll need the extra range.


The amount of time it spends balancing depends on many factors, basically how unbalanced the battery is. The very first balance is expected to take longer; it may even take several hours, or it might give up and try again next time you charge to 100%.

So i leave it plugged in - with the trickle charging?

I think it requires 1 hour or so until it finishes... After that - right?

Well, reconnecting didnt work now. I plugged it again and says charge complete.

So next time... Leave it on to see what happens.

Does it stop automatically? Or i have to stop it once the balancing finishes?

I dont have the app because it doesnt work in my country. So i have to physically walk over there and check.

It might be but you would be one of a very few interested in such application.

The cycling of an EV battery is different to a stationary battery. Not many EV batteries are cycled between a low and high SOC on a regular daily basis and the charge rate is typically lower (~0.1 C or lower, except for occasional DC fast charging) while stationary applications tend to cycle much more and settle on ~0.2 C for charging, although some drive them harder up to 0.5 C.

The battery pack will outlast the car.

I thought about doing a DIY LFP pack for home but the server rack units I use were already cheap enough. I can view the 16S cell voltage data on their displays while my Home Assistant tracks min, max and cell delta for each unit, e.g.:

View attachment 28168


It would be interesting to know how the LFP pack voltage responds to charging to 100%. Can at least see what average cell voltage they are using. Should be something in the range of 3.6 V/cell I'd expect.

My NMC pack peaked at 441 V the other day when charged to 100%.
441/104 = 4.24 V/cell.

4.20-4.25 V is the typical upper charge voltage for NMC depending on cell brand.

MG4 pack details:

View attachment 28169

Where did you get this information about the batteries of mg4? The chart comparison and the image of the battery

 

[wattmatters]

Where did you get this information about the batteries of mg4? The chart comparison and the image of the battery

Can't recall off top of my head. There are several sites with battery spec data.

Does it stop automatically?

Yes.

The car's battery management system will look after it. If it has completed charging it will stop.

There really isn't a lot you need to do other than plug it in and set the maximum charge level - the car will take care of the rest.

I was out a little earlier and when I got home plugged in to top the car up:

That's the power draw reported by my circuit monitoring for the EV charger. Can see it pulling ~7 kW, then at the end it drops down to a trickle of ~50-150 W for 5-10 minutes, then stops completely, other than the 1-2 W of idle power the EVSE itself consumes.

NMC models will do this balancing even at SOCs less than 100%. You can do that with NMC chemistry due to the SOC-voltage relationship but you can't really do it with LFP. LFP needs to be at/near 100% to do a cell balance.

 

[Ethernea]

I was out a little earlier and when I got home plugged in to top the car up:

View attachment 29194

That's the power draw reported by my circuit monitoring for the EV charger. Can see it pulling ~7 kW, then at the end it drops down to a trickle of ~50-150 W for 5-10 minutes, then stops completely, other than the 1-2 W of idle power the EVSE itself consumes.

NMC models will do this balancing even at SOCs less than 100%. You can do that with NMC chemistry due to the SOC-voltage relationship but you can't really do it with LFP. LFP needs to be at/near 100% to do a cell balance.

Uhm sorry. Im new with many terms...

What is SOC?