Voltage shown in “Electrical information”

Hello, is there anybody who can confirm that the voltage displayed in
“Electrical information” message centre is real voltage of the HV battery?
When 100% charged this is 454V
I know the battery has 108 serial elements and this would mean that when 100% charged one single cell is having a voltage of 454 : 108 = 4,2V.
4,2V is exactly the top charge cut off voltage of a lithium cell and this would mean there is no top protection buffer in the MG, like p.e. Nissan who stops at 4,1V.
Is there somebody who knows more about this?

When the battery is full, the MG has no regen, which suggests that if there is a buffer it’s very small.

Thinking out loud, I reckon it can take 10 miles or 2kWh before you notice regen coming back.

When I can predict my usage, I will generally run my car down to about 50 miles, about thirty percent, and charge it to 120 to 130 miles, so maybe up to 85%.
I only fully charge if I’m going on a long journey.

That is complete other way to explain that the MG is having a small top protection buffer.
I made my conclusion from the fact that 108 x 4,2V = 454V exacltly what is displayed by “Electrical information”
A fully charged Lithiumcell is 4,2V.
But I need to know sure that this displayed voltage (454V) is straight coming from the HV battery so not somewhere in the converter or so.
Can anybody confirm this?

From testing with OVMS queries, the top limit appears to be 97%…not sure on bottom limit. I would not leave it there too long if you can help it. But at least there is thermal management on the pack

And yes that 450 V is direct from the battery, no conversion factor

“Would not leave it there too long” You mean don’t charge to 100% if you don’t need the car the next day or only for short distance.
If he 454V is coming straight from the battery it means that the voltage on one cell is 454:108= 4,2V. That means fully 100% charged without protection buffer. 4,2V is the charge cut off voltage of a lithium cell.
I charge to 80% if possible, but every 5 times to 100% just for performing an equalization.
When make long distance also charge 100% of course.

Taken from the manual:
Parameters of High Voltage Battery
Item Parameter Values
Type Ternary lithium ion battery
Rated Energy, kWh 44.5
Rated Voltage, V 394.2
Weight, kg 283
Waterproof Grade IP67
So could it mean the voltage we see could be from the inverter ?

That is the RATED voltage.
The rated voltage of one single lithium cell is 3,65V
This is matching exactly: 394,2:108= 3,65
100% charged lithium = 4,2V and this is slowly going down to about 3,5V when reaching 10%.
So the voltage is not always the same, rated voltage is the overall average voltage.
I can’t make other conclusion that the voltage shown on the dasboard is the voltage direct from the HV battery, as MikeRES said allready.
You see it going down after using the car.
Actually, you could use this voltage to see how many charge you have left.

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@Johnberg51 I’ve been thinking about this a bit, and do we have any more information about the cells and chemistry used in the MG. I highly doubt SAIC are pushing the cells up to the absolute max as it is just not worth the damage over the 7 year warranty for the small performance gain. Euan McTurk may be able to shed some light on this.

As far as I know MG is having Lithium Nickel Manganese Cobalt cells.
They have about 1000 to 2000 charging cycli. Let’s say 1500
1500 x 200 Km = 300.000 Km
So I think MG certainly will reach the garantee which means 70% capacity left.
70% is a very poor battery!!
I also read that NMC cells could be charged to 4,4V, maybe that top protection buffer is not so important anymore???
But if you could reach 90% after 8 years with a little charging regime, why should you not do this? I drive only 8000 Km a year.
I am very curious to the conclusion of Euan McTurk
On this website some info of types of Lithium:
https://batteryuniversity.com/learn/article/types_of_lithium_ion

I have a Nissan Leaf at 80k miles and 80% health so if the MG makes it to 200k and 70%…I would be very pleased…bear in mind almost all cars after 200k are considered end of life. Also I would have saved at least £20,000 in fuel costs…and still have a good second Life battery

@mikeRES
I read that Nissan limits charging the cells at 4,1V
I only can make conclusion that MG is charging at 4,2V which should be the max of Lthium.
I am a liitle worried about that.
I am not so interested in making a lot of miles, but I would like to have a 90% healthy battery after about 8 years or so.
Charging to 80% (about 4,0V pro cell) could double the amount of charging cycli.

@Johnberg51 You’re probably right.

OVMS:
v.b.c.voltage.max 4.11119,4.1139,4.09085,4.09085,4.09356,4.08881,4.09356,4.08881,4.11119V
v.b.c.voltage.min 4.10305,4.10305,4.06373,4.08542,4.06508,4.08542,4.05424,4.08136,4.10441V
v.b.voltage 435.5V
v.b.soc 83.1711%

When I see the image I see a possibility of 18 modules and in OVMS I see 9x cell voltages.
9 equals 12 “something” is also 108, interesting… Above 80% SOC the voltages are around approaching 4.1V :slightly_smiling_face:

From a Dutch website Google translated:
The MG ZS battery has a much higher energy density. It has eighteen modules, each with six blocks in series of six cells connected in parallel. Such a block is good for 110 Ah, and 108 blocks of 3.65 V provide a battery voltage of 394.2 V. This brings the capacity to a small 44 kWh. That is less than the Maxus battery, but at a much lower weight: 277 kg.

OVMS on your post is showing about 4,10V per cell, but at what SOC?
When 100% fully charged the car dashboard is showing 454V
454 : 108 = 4,2V
4,2V is the voltage of a really top charged lithium cell without any protection buffer.
Ebikes also are charged at 4,2V per cell.
If the car display should have displayed 108 x 4,1 = 443V @100% I would be much more happy :grinning:

From a Youtube of Björn Nyland and I also read on a Thai website that the battery of th MG is having a total battery capacity of 50 Kwh.
This could explain that 4,10V per cell when fully charged.
If this is true I would be really happy, but nobody can confirm this.
But that 4,10V is contradictory with the 454V shown in the car display.


Use Google translate :grinning:

I did for you:
But if you want me to guess about the battery price of the MG ZS EV, I would like to take an example of a chevy bolt battery to compare it. The chevy bolt has about 60 kWh or 288 cells battery. The Bolt is at $ 15,000 or 450,000 baht, while the MG ZS EV has a battery of 50 kWh, but can be used only 44.5 kWh because the software lock can not use more than 90% SoC (State of Charge), so I look. That the battery cost of MG should be cheaper than 400,000 baht per pack (excluding tax for some countries) And if you think about it in a straightforward way, one module will drop approximately 25,000 baht (this is a fun calculation From the world battery price Which is expected that in the future in the next 8 years, the battery price will be 1 times cheaper than before

@Johnberg51

I posted all the details of the cells and battery:

Yes, I know that website also :). The cells are 4.1 at a SOC of 83%. But 435.5/108 = 4.03…

I’ll let the battery equalize and check cell voltages again. I’m not sure how OVMS is getting the cell voltages and why it are just 9.

I really would like to know how much the cell voltage is when the car is showing 100% charged.
That is the only truely indication of the SOC
Lithium:
100% = 4,2V
90% = 4,1V
BTW what about the Thai info that we actually are having a 50 Kwh battery?

I think, the battery is 50 kWh with 44.5 kWh useable (90% DoD). It uses a later NMC chemistry (NMC532?) that can actually be happily used up to 4.4V (change in cathode material I think allows the additional 0.2V).

Next time I do a full charge I will check cell voltages for you (might be a while thanks to lockdown).

Bear in mind for cycle ratings, you do not use a “full cycle” unless you go from absolute 0 to 100% so you can probably say double that for EV usage, so 2000 cycles to 80% health, works out at least 4000 EV use cycles so that is like once a day for 11 years. TBH I think there will be better EVs out there by then I would want to be hacking!


This is the battery label under the car @mikeRES

I also read that NMC batteries could be charged to 4,4V
One thing is sure: when charged to 100% the voltage on the dashboard is showing 454V and I know that the battery is having 108 serial blocks.
So the voltage if one block is 454 : 108 = 4,2V
With conventional lithium this should mean 100% SOC
But maybe the secret is in the fact that NMC could be charged to 4,4V
So if charged to 4,4V it could be 50 Kwh and 4,2V for our battery could mean 90% SOC. But this are all assumptions :roll_eyes:

I still wonder: is manual charging to 80-85% useful to spare the battery for the future?