MG5 won't balance charge (2020 pfl exclusive)

Suspected so :)

Ok so the profile is right the info is odd

Can anyone with car scanner look at the main dashboard screen and see what their CMU’s say?

Sigh
 
Pebblefeline said:
Set to mg5 profile
It turns out they aren’t module s they are the Cell Monitoring Units that govern groups of cells
I believe the long range has 96 cells so in groups of 4 with a CMU in each? Giving 24 CMU’s?
These re reported by car scanner and each CMU reports in the cell voltage to the Bms I think.

Can anyone else with car scanner look at their CMU readings?

Now we are so far beyond my knowledge, I started reading a CMU research paper and ……. Well I got a headache
Click to expand...
Yes, my CMU readings are 3.22V when fully charged.
 
Gomev said:
As a rough calculation from 10% of actual size (rounded - 61kWh or should it be 57 usable ?) would need approx 55kWh (51kWh).
Onboard charger is 6.6kW so would require over 9 (8.5) hours plus balancing time to go 10-100%. - Just about a full at work :)
Can't remember if the 5 Trophy has 11kW charging, if so times obviously reduce a fair chunk.

All rough guesstimations.
Click to expand...

Balance day! Didn’t leave until 5.15pm

img_3546-png.34716
 

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I did a few weeks ago on my 74 plate trophy 7% to 100% charge with a (7kW) home charger at a rate of 6.5kW it took 8 hours 58 minutes for 60.48kWg of energy including balancing.
 
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walter said:
I did a few weeks ago on my 74 plate trophy 7% to 100% charge with a (7kW) home charger at a rate of 6.5kW it took 8 hours 58 minutes for 60.48kWg of energy including balancing.
Click to expand...
Sounds about right if that's the power supplied. 93% added of 61kWh is about 57kWh or 93% of usable 57kWH is 53kWh.
Take away conversion losses from supplied 60.48 from that added and it could match using either usable or total capacity.
 
Gomev said:
Sounds about right if that's the power supplied. 93% added of 61kWh is about 57kWh or 93% of usable 57kWH is 53kWh.
Take away conversion losses from supplied 60.48 from that added and it could match using either usable or total capacity.
Click to expand...
You can only access/charge the ‘usable’ battery capacity.
 
MickeySw said:
You can only access/charge the ‘usable’ battery capacity.
Click to expand...
I don't think the buffers top and bottom are kept separate in different cells from the usable part, it is still a 61kWH battery pack, the whole of which gets charged and discharged, just the very top and very bottom isn't usable.
 
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Gomev said:
I don't think the buffers top and bottom are kept separate in different cells from the usable part, it is still a 61kWH battery pack, the whole of which gets charged and discharged, just the very top and very bottom isn't usable.
Click to expand...
The theoretical capacity of a battery pack is derived from the maximum capacity of each cell, e.g. 150Ah from 2.5V-4.3V.

The BMS limits this voltage range (e.g 2.8V -4.1V) which will slightly decrease the overall capacity but greatly increase the longevity of the battery.

The top/bottom buffers can therefore not be accessed.
 
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MickeySw said:
The theoretical capacity of a battery pack is derived from the maximum capacity of each cell, i.e. 150Ah from 2.5V-4.3V.

The BMS limits this voltage range (e.g 2.8V -4.1V) which will slightly decrease the overall capacity but greatly increase the longevity of the battery.

The top/bottom buffers can therefore not be accessed.
Click to expand...
Precisely, they are software buffers for the whole battery preventing overcharging and overdraining, not physical entities in their own right.
I think we are agreeing but terminology is getting in the way. The usable battery is as you describe restricted by the BMS from using the entirety of those cells capacities whereas your original comments inferred they were separate cells that were in effect held in reserve and never accessed or charged.

MickeySw said:
You can only access/charge the ‘usable’ battery capacity.
Click to expand...
 
Pebblefeline said:
Set to MG5 profile.
It turns out they aren’t modules, they are the Cell Monitoring Units that govern groups of cells.
I believe the long range has 96 cells so in groups of 4 with a CMU in each? Giving 24 CMUs?
These re reported by car scanner and each CMU reports in the cell voltage to the BMS I think.

Can anyone else with car scanner look at their CMU readings?
Click to expand...

I have a 2021 pfl, same as you, reading 24 CMU's with CarScanner set to MG5EV. When set to MG5 it only had reading for internal combustion. Min/Max cell voltage 3.25/3.26V for each CMU, battery cell Min/Max 4.15/4.16V.

This is with a 97.12% SOH @27k miles.

My previous pfl 2021 plate had 100% SOH at 41k miles, I charged on 7kW home charger most nights to 100%, zero degradation. I'm assuming the previous owner of my new to me car used a lot of fast chargers for it to be at 97% at 21k miles when I got it.
 
AndyB87 said:
This is with a 97.12% SOH @27k miles.

My previous pfl 2021 plate had 100% SOH at 41k miles, I charged on 7kW home charger most nights to 100%, zero degradation. I'm assuming the previous owner of my new to me car used a lot of fast chargers for it to be at 97% at 21k miles when I got it.
Click to expand...
Was your previous PFL also standard range as there is a rumour going around that some got ‘rejected’ LR batteries and therefore SoH remained 100% indefinitely..
 
MickeySw said:
Was your previous PFL also standard range as there is a rumour going around that some got ‘rejected’ LR batteries and therefore SoH remained 100% indefinitely..
Click to expand...
It was a 2021, so yes, before they released the long range. I can't see that being the case though as my car was probably manufactured late 2020, unlikely they even had developed the longer range battery by that point.
 
AndyB87 said:
It was a 2021, so yes, before they released the long range. I can't see that being the case though as my car was probably manufactured late 2020, unlikely they even had developed the longer range battery by that point.
Click to expand...
According to the EV database, LR models were available from July 2020, hence they were built alongside your car.

It’s very probable that manufacturing teething problems could result in LR packs with insufficient capacity. Recycling these into SR models would be way more cost effective than ‘bin’ them.

Fact is that NMC batteries loose capacity due to age and ‘usage’. Yours still showing ‘zero visible degradation’ after 41k is therefore unlikely the full story.

At the end of the day, few (if any) would notice even a 10% reduction in SoH during their daily drive.
 
AndyB87 said:
Interesting, I wasn't aware of this. So for them to be manufactured as LR - are we talking about the Roewe Ei5 as opposed to the UK spec MG5?
Click to expand...
ev-database.org

MG MG5 EV Long Range

All details and specs of the MG MG5 EV Long Range (2020-2022). Compare price, lease, real-world range and consumption of every electric vehicle.
ev-database.org ev-database.org
 
Hi. I have an MG5 Exclusive. I charge at home with an Easee charge. I always charge to 100% when I charge, yet the car complains almost all the time about needing a BMS balancing charge. Simply reversing from my drive causes the message to pop up. Also I have read here that some people can take their car down to 10% or less: I can't - I get the snail mode limiting power, even at 27% or higher? Is this in line with other people's experience?
 
hastykev said:
I get the snail mode limiting power, even at 27% or higher? Is this in line with other people's experience?
Click to expand...

No, or at least it certainly isn't for me. On one occasion I ran it down to below 5% and didn't experience any power limiting (just a realisation that I needed to be very gentle with my right foot!).

How old is your car and what mileage have you covered? Have you owned it from new? Mine is a 2022 PFL, approximately 18.5k miles, owned from new.
 
hastykev said:
Hi. I have an MG5 Exclusive. I charge at home with an Easee charge. I always charge to 100% when I charge, yet the car complains almost all the time about needing a BMS balancing charge. Simply reversing from my drive causes the message to pop up. Also I have read here that some people can take their car down to 10% or less: I can't - I get the snail mode limiting power, even at 27% or higher? Is this in line with other people's experience?
Click to expand...
It’s rare, but I have heard of MG5’s suffering from what appears to be a voltage imbalance caused by a weak cell.

I would start with a hard reset, I.e. disconnect the (-) pole of the 12V battery for a few minutes.

If that doesn’t make a difference, invest in a OBD dongle and check the cell voltages yourself or bring the car to the nearest dealer.
 

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