MG5 won't balance charge (2020 pfl exclusive)

[Petriix]

I've realised that my MG5 isn't balance charging once it gets to 100%. Previously the charge rate would taper off as it gets closer to full, dropping steadily from 7.3kW to around 2kW before spending a couple of hours with power as low as 500W while the cells balance.

Now it's getting down to 2kW then simply stopping. I noticed this morning that the fully charged voltage was 403V where it would normally be 405V.

I thought it might be an issue with Intelligent Octopus Go so I didn't think too much about it, I just switched off smart charging and put it on manual but it did exactly the same thing. On investigation it seems it hasn't balanced properly since October, before the most recent service.

I don't if anyone else is experiencing this or something similar. It's like the dodgy BMS issue the ZS faced. I'm not sure if I've been given a dodgy software update or if something else has gone wrong but it's definitely not working properly.

I have a feeling it's going to be difficult to get MG to understand, acknowledge and diagnose the problem so any advice would be greatly appreciated.

Here's what a normal balance charge looks like:

And here's what's happening now:

 

[Jomarkh]

I was thinking the same on my last balance, it didnt seem to continue the few hundred watts balance.
What SOH are you at and do you know what was update for that may have caused the issue?

 

[Fokmg]

Is it worth charging most of the way using normal; octopus go intelligent and then swap over to the granny charger for the final few % and the balance charge ?
This way you could eliminate either a BMS fault or Octopus issue?

 

[Petriix]

I've spoken to the garage who tell me there's no record of any software update since 2023. Next thing is to try the granny charger in case it's an issue with the Zappi; harder to monitor but I should be able to discern the power through my smart meter data if not the Myenergi app (will look like home usage). I can't see how Octopus could be involved if it's happening with smart charging disabled.

 

[Gomev]

I suspected mine of this before I swapped it 8 months ago. I couldn't establish any proof but did notice differences as you have described.

 

[emmrecs]

Mine is a 2022 PFL and I think it is doing exactly this, and not balancing.

For the month of January I have been meticulously recording (in a spreadsheet) ALL journey data (SOC, miles covered, Range, average m/kWh, both per journey and cumulative for the month). The car is due for its third service and first MOT next month and I want the data to be able to "discuss" the issue with the dealer's service department.

One thing that has emerged is that estimated range for 100% battery on January 1st was 240 miles (following a total reset of Current Journey and Cumulative Total data), on January 15th it was 205 and on January 24th it was 187! Also, at no time was the "expected average" of 2 miles per 1% battery depletion actually achieved. Currently it shows 87% and 155 miles range. One of the "lowest" figures I saw was 27% and 39 miles.

I assume an MG dealer's diagnostics can show whether or not the cells are balanced?

 

[Petriix]

@emmrecs I wouldn't be worried about the estimated range. It's the overall pack voltage when fully charged and cell min/max voltages which the garage should be able to show you.

 

[emmrecs]

@Petriix

Thanks for your post.

I'm not worried about the estimated range, though it does concern me to see it drop so much between charges over a comparatively short period of time.

The pack voltage etc. figures you refer to will be interesting to see!

 

[Pebblefeline]

Was the 205 and lower figures what you had at 100 percent after a reset?

Or was this figure after the car had been driven?

 

[emmrecs]

No reset.

Because I keep another spreadsheet showing monthly mileage and consumption figures, I normally do a reset only on the first of the month.

 

[Pebblefeline]

That’s why the total is low though on the gom.

I imagine you mi/kWh figures are around 3.3 maybe in January?

The 240 miles at reset bases that figure closer to 4mi/kWh.
4.18 mi/kWh to be precise

So the dropping figure on the gom is based on your current driving efficiency. And it will drop quickly.

Your figures look reasonable.
I expect to get 170 to 190 miles in the winter, and 220 to 230 in summer.

The 2 miles per percent is just a sort of benchmark average.

 

[emmrecs]

I imagine you mi/kwh figures are around 3.3 maybe in January?

They're actually showing currently as 2.7.

The 2 miles per percent is just a sort of benchmark average

Agreed, but it is what I have been seeing during most of the nearly three years I've owned the car.

the dropping figure on the gom is based on you current driving efficiency

Again, agreed. But I don't think my driving style has changed that much over those three years!

But the topic of this thread is about whether balancing is occurring and if not, why not, and is that "lack of balance" adversely affecting overall performance?

 

[Pebblefeline]

Yes true my post was poorly related to the thread

But your 2.7 mi/kWh figure isn’t affected by balancing, overall capacity will be but not efficiency unless I am missing something. At 2.7 your range sounds realistic frankly and the car is working as it should.

Have you put an OBD reader on your car with car scanner? Then you can see the individual module voltages and know definitively.

I check mine now and then and see normally 0.01 V variations

The op sounds as though they may have a problem and have some data that backs up the hypothesis.
However they to my knowledge have not looked at their cell voltage either.
Which seems like the first step to me to confirm if the modules are showing a balance issue.

Your post sounded like you were concerned your gom was showing reduced range during the coldest period we have had I the uk for some time and you were drawing a correlation that you were concerned about your 5 not balancing.
I wanted to reassure you, as I suspect that your issue is simply short drives in the cold when the battery heater runs and eats power. This would be bound out for me by your consumption figures.

I would suggest the investment in an obd scanner and car scanner app will put your mind at rest as you can see reported voltages for modules.

Apologies if my post sounded off topic.

 

[MickeySw]

I thought it might be an issue with Intelligent Octopus Go so I didn't think too much about it, I just switched off smart charging and put it on manual but it did exactly the same thing. On investigation it seems it hasn't balanced properly since October, before the most recent service.

It could still be an EVSE issue, if it had a recent (October?) update that terminates the process once the current drops below a certain level?

Using the granny as @Fokmg suggested would shed some light.

It could also be (in theory at least) that the cells are already balanced? As @Pebblefeline mentioned, you can easily check that yourself.

 

[Gomev]

Mine is a 2022 PFL and I think it is doing exactly this, and not balancing.

For the month of January I have been meticulously recording (in a spreadsheet) ALL journey data (SOC, miles covered, Range, average m/kWh, both per journey and cumulative for the month). The car is due for its third service and first MOT next month and I want the data to be able to "discuss" the issue with the dealer's service department.

One thing that has emerged is that estimated range for 100% battery on January 1st was 240 miles (following a total reset of Current Journey and Cumulative Total data), on January 15th it was 205 and on January 24th it was 187! Also, at no time was the "expected average" of 2 miles per 1% battery depletion actually achieved. Currently it shows 87% and 155 miles range. One of the "lowest" figures I saw was 27% and 39 miles.

I assume an MG dealer's diagnostics can show whether or not the cells are balanced?

That is the correct way to find the SOH if you do not have access to an OBD reader. At 100% SOH your 5 Exclusive LR should show 250 miles GOM at 100% when accumulated trip is reset.
As yours showed 240 this represents a SOH of 96%. If you are doing this at lower SOC %ages then you will need to also do a reset on the accumulated trip and pro rata for whatever % you are at (in your example at 155 GOMx100/87 SOH) not always as accurate as doing it at 100% but a reasonable guess. The key is the accumulated trip has to be reset.
This of course does not show you how well balanced the cells are you, will need an OBD for that and there are many threads on here re those.

 

[Coulomb]

As yours showed 240 this represents a SOH of 96%.

Remember also that this estimated SoH may rebound slightly in summer.

 

[Fluffykins]

Yes true my post was poorly related to the thread

But your 2.7 mi/kWh figure isn’t affected by balancing, overall capacity will be but not efficiency unless I am missing something. At 2.7 your range sounds realistic frankly and the car is working as it should.

Have you put an OBD reader on your car with car scanner? Then you can see the individual module voltages and know definitively.

I check mine now and then and see normally 0.01 V variations

The op sounds as though they may have a problem and have some data that backs up the hypothesis.
However they to my knowledge have not looked at their cell voltage either.
Which seems like the first step to me to confirm if the modules are showing a balance issue.

Your post sounded like you were concerned your gom was showing reduced range during the coldest period we have had I the uk for some time and you were drawing a correlation that you were concerned about your 5 not balancing.
I wanted to reassure you, as I suspect that your issue is simply short drives in the cold when the battery heater runs and eats power. This would be bound out for me by your consumption figures.

I would suggest the investment in an obd scanner and car scanner app will put your mind at rest as you can see reported voltages for modules.

Apologies if my post sounded off topic.

What software are you using?

 

[Pebblefeline]

Car scanner with an old Carly obd

 

[Fluffykins]

Car scanner with an old Carly obd

Thanks. Is that on Android or iOS?

 

[Pebblefeline]

I use it in iOS but I believe it’s in android as well