ZS EV Mk2 51 kWh LFP battery - What is Your Voltage When Full?

[Peter WA]

402V

Amazing how close your cell voltages are 3.35 to 3.36V.

Interesting to see 99.9% SOC, not 100%, I wonder if your battery did properly balance after charging to full.

I can only wish mine was like that too...

 

[natasha y]

Amazing how close your cell voltages are 3.35 to 3.36V.

Interesting to see 99.9% SOC, not 100%, I wonder if your battery did properly balance after charging to full.

I can only wish mine was like that too...

It was reading 100% on the dash. I cut it short as the ambient temp was quite high and the fan had cut in. It usually puts up a message once balance charged. I have only DC charged once in just over a year from new and balance charged three times. Max separation any time I have checked has been 0.01v

 

[Peter WA]

Max separation any time I have checked has been 0.01v

When do you usually check this?

Reason I ask: When my car first ticks over to 100%, before (not actually) balancing, the highest cell voltage is 3.65V. Since yours is only 3.35V, something is different. Well, yours is better.

Although 3.35V, with no load, would be closer to 98% charged than 100%, just from experience with LFP cells in my home battery.

Did you use Car Scanner to get that screenshot, or a different app? Does it allow to read out the software versions of all ECUs?

I'd love to compare. My list looks like this right now:

ATC REL_BEV_ZS_Z_031
VCU blrv0660
EPS ZemrV08bRs
ABS 863443_NW5DR2b2Ee2b7oBWdfjhTA
GWM 0075011060
TBOX SNMKP02SAU
BCM 41762494 $
PEPS $Rev: 374
PLC 2035431312
SRM EP21MCE570
SCU 194177873 C1708
EVCC S007R7����
IPK 5.0.3.3
ICE 91.1.0.5
RDRA SWCR.16.16
TPMS QY1105A131

 

[natasha y]

When do you usually check this?

Reason I ask: When my car first ticks over to 100%, before (not actually) balancing, the highest cell voltage is 3.65V. Since yours is only 3.35V, something is different. Well, yours is better.

Although 3.35V, with no load, would be closer to 98% charged than 100%, just from experience with LFP cells in my home battery.

Did you use Car Scanner to get that screenshot, or a different app? Does it allow to read out the software versions of all ECUs?

I'd love to compare. My list looks like this right now:

ATC REL_BEV_ZS_Z_031
VCU blrv0660
EPS ZemrV08bRs
ABS 863443_NW5DR2b2Ee2b7oBWdfjhTA
GWM 0075011060
TBOX SNMKP02SAU
BCM 41762494 $
PEPS $Rev: 374
PLC 2035431312
SRM EP21MCE570
SCU 194177873 C1708
EVCC S007R7����
IPK 5.0.3.3
ICE 91.1.0.5
RDRA SWCR.16.16
TPMS QY1105A131

Using car scanner. Don’t do a regular check due to not ever having much cell differential. 95+% charged off rooftop pv so < 4kW. Generally only charge to 80-90% to avoid overheating in Perth weather and to avoid diminishment of kers at 95%. Will try to interrogate software tomorrow.

 

[Peter WA]

Using car scanner.

I've tried using car scanner too just to see, but I don't get any useful info for my car from it. Are you using the paid version or the free one?

In the ECU list BMS is one of the tick-boxes, but it is off by default, and when I pick it, no data comes back. Very weird. So we actually can't compare the most important software version.

As an update:
After charging from ~8% to 100% two times in a week I still did not get any 'equalising'. The second time charging kept going for over an hour at 9A (AC draw from my charger), then one cell hit the 3.65V cut-off, charge current dropped to 3A, and completely stopped after another 3 minutes. The discrepancy between lowest and highest cell is still very big, and overall voltage when fully charged is getting lower and lower.

I will contact the dealership and hope they agree this is an issue, and either install a BMS software update (if one is available), or contact MG to investigate further and perhaps make an update.

 

[natasha y]

I've tried using car scanner too just to see, but I don't get any useful info for my car from it. Are you using the paid version or the free one?

In the ECU list BMS is one of the tick-boxes, but it is off by default, and when I pick it, no data comes back. Very weird. So we actually can't compare the most important software version.

As an update:
After charging form ~8% to 100% two times in a week I still did not get any 'equalising'. The second time charging kept going for over an hour at 9A (AC draw from my charger), then one cell hit the 4.65V cut-off, charge current dropped to 3A, and completely stopped after another 3 minutes. The discrepancy between lowest and highest cell is still very big, and overall voltage when fully charged is getting lower and lower.

I will contact the dealership and hope they agree this is an issue, and either install a BMS software update (if one is available), or contact MG to investigate further and perhaps make an update.

Using the pro/paid version. Sounds weird on the battery cell differential especially when mine is nigh on perfectly balanced all the time.

 

[Coulomb]

one cell hit the 4.65V cut-off,

Are you sure about that number?

I suspect that CarScanner is using the wrong scale factor for converting raw Can bus values to displayable cell voltages. Did you select a suitable car model in the settings?

 

[Peter WA]

Are you sure about that number?

I suspect that CarScanner is using the wrong scale factor for converting raw Can bus values to displayable cell voltages. Did you select a suitable car model in the settings?

Sorry, typo, 3.65 of course. Fixing it above.

Using the pro/paid version.

Is the connection profile in that version of car scanner still called "MG MR5EV / Marvel EV/ MG ZS EV Facelift 2022'?

Would you be able to check whether you can read out a software version for the BMS? It's in the section called 'ECU Identifiers'.

If you get that info (I don't get it, and I don't get it in OVMS either), that might be an indication of an issue already. Actually, I might just disconnect the 12V battery to see if a proper full reboot of everything makes a difference.

 

[natasha y]

Is the connection profile in that version of car scanner still called "MG MR5EV / Marvel EV/ MG ZS EV Facelift 2022'?

Would you be able to check whether you can read out a software version for the BMS? It's in the section called 'ECU Identifiers'.

If you get that info (I don't get it, and I don't get it in OVMS either), that might be an indication of an issue already. Actually, I might just disconnect the 12V battery to see if a proper full reboot of everything makes a difference.

Yes, same profile but won’t read the BMS. I tried, Sorry
Btw my max/min cells exactly equal again/still.

 

[Peter WA]

Yes, same profile but won’t read the BMS. I tried, Sorry
Btw my max/min cells exactly equal again/still.

Thank you so much for being so responsive and helpful. If we can't get the BMS software version number to compare, there is no point for me upgrading to the pro version of the app. In that case I just assume my OVMS gives me all there is to see.

Regarding cell voltages: even my unbalanced pack will show a similar minimal discrepancy between cells when the pack is somewhere in the middle of the SOC range (say between 10 and 90%). The only reason I still see any difference at all is that I get an extra digit (3 decimals), while the app only shows you 2 digits. You would not see a 3mV difference, it gets rounded to the save value.

The reason that we have those tiny differences is that LFP cells have an extremely flat voltage curve. The real difference only becomes apparent right at both ends. I don't want to go down to 0%, so I am looking at 100%.

The very first screenshot you posted, where you had 99.9% SOC was 3.35V. The one just now, 77% SOC shows 3.32V. You had another one, 72% SOC, also 3.32V. The difference is very small, and most of that voltage drop will happen in the first 1% of discharging, when what is called 'surface charge' is used.

I would be curious to see where your voltage difference goes to right at the end of a charge to 100%, just before the car stops charging. I would assume that the highest cell goes to 3.65V, just like it does for me. The question is where the lowest cell is at that time.

Mine is around 3.37V at that time, which is much too low for my liking. Anything over 3.45V for the lowest cell, I'd be happy with. By my estimation that difference is enough to hide 10% of the cell capacity, which might go unused in my battery pack.

 

[LeedsLoiner]

Using the 13amp charger that came with the car. Is this a granny charger?
Charged over two days from 60% and left charging this morning until it turned itself off. See attached for the voltage after unplugging.

 

[Coulomb]

the 13amp charger that came with the car. Is this a granny charger?

Yes.