MG4 51kWh LFP Battery Health

[AlC]

It'd be interesting to know the dates as well as the milage on that graph for those SOH readings, as I think calendar degradation plays a big part.

Somewhat alarming that the downward trend doesn't seemed to have plateaued after a little over 2 years.

 

[EVentropy]

Update, Gen 1 (Sept 22), nearly 30k miles - Recent service Main Dealer = SoH = 100%, below is from car scanner - Basic 51kW SE

View attachment 33922

Mine is following that trend at 20k km. Actually lower SOH.
Does the VNCI vd13 give you access to cell voltages via SIPS? Also all the data the dealers
Get. I know you have to get a Co account etc and pay . Yeah , I know wrong thread.

 

[Tig170]

It'd be interesting to know the dates as well as the milage on that graph for those SOH readings, as I think calendar degradation plays a big part.

Somewhat alarming that the downward trend doesn't seemed to have plateaued after a little over 2 years.

I didn't record the dates, so here is what I've got via car scanner:

 

[gdog]

Didn’t someone say LFP degradation is Calendar based at about 3-4% PA. So at two years old 92-94% would tally up?

And indeed 68-76% at 8 years mark. (Edited to 8yrs)

Funny Coincidence that

 

[T1 Terry]

Didn’t someone say LFP degradation is Calendar based at about 3-4% PA. So at two years old 92-94% would tally up?

And indeed 70-79% at 7 years mark.

Funny Coincidence that

That's yet another myth. We have LFP house systems 12 yrs old at better than 100% capacity tested at the factory 2C discharge rate, so no degradation. They should be down to 64% to 52% capacity if that 3 - 4% degradation was correct.

Just one of the fallacies put out by misreading the information supplied by the manufacturer, that 3 - 4% degradation per yr only occurs if the battery is held at 100% SOC for that period of time .... but even then, it is an assumption using accelerated testing .... if you get around 1% after 3 mths, then that must mean 3 - 4% over 12 mths and so on.

T1 Terry

 

[gdog]

That's yet another myth

Fingers crossed. It’s probably just an algorithm in MG code for SOH.

I have 2+ year old LFP home storage and I think it is still near 100%. Need to do a full discharge/charge some time to confirm

 

[T1 Terry]

My guess is the steady loss of SoH is the real capacity catching up with the claimed capacity as far as the computer sees it. When it drops to 42Ah capacity, the degradation will slow to a much more realistic figure of less than 1% per yr.

The calculations I've made for the true 51 capacity are 104 cells X 125Ah X 3.2V nom. = 41.6kWh.
The nom. LFP battery voltage is a solid known figure, the 104 cells is also a known figure. Working backwards 51,000Wh/3.2V = 15397.5Ah/104 cells = 153.24Ah per cell.

Considering LFP isn't as energy dense as NMC, the same size battery box holds the same number of cells, 104, yet it is supposed to have a capacity of 63,000Wh. 63000Wh/3.7V nom. = 17,027Ah/104 cells = 163.7Ah ..... that's around 1% better capacity in the same size cell ....... really, if that was the case, no one would use NMC chemistry cells would they.
Add to this the fact MG derated the battery capacity in later models to 49kWh and no doubt this figure is also inflated using 3.65V as the nom. cell voltage, using the equations above comes out to 129Ah per cell ..... I still doubt it is even that much ...... Many cell/battery manufacturers like to use the other myth that only 80% of the capacity can be used, so they add the other 20% to their cell/battery capacity claims .... use this on the 51kWh claim and what figure do you come up with .......

I just realised I posted all this in the start of this thread .... sorry about that folks

T1 Terry

 

[ReintjeWA]

Some interesting conclusions about battery life

https://www.sciencedaily.com/releases/2024/12/241209122933.htm

www.mgevs.com

There was this study that implies the current testing regimes are pretty inaccurate anyway, when it comes to expected battery life.

 

[AlC]

My guess is the steady loss of SoH is the real capacity catching up with the claimed capacity as far as the computer sees it. When it drops to 42Ah capacity, the degradation will slow to a much more realistic figure of less than 1% per yr.

The calculations I've made for the true 51 capacity are 104 cells X 125Ah X 3.2v nom. =41.6kwh.
The nom. LFP battery voltage is a solid known figure, the 104 cells is also a known figure. Working backwards 51,000wh/3.2v = 15397.5Ah/104 cells = 153.24Ah per cell.

Considering LFP isn't as energy dense as NMC, the same size battery box holds the same number of cells, 104, yet it is supposed to have a capacity of 63,000wh. 63000wh/3.7v nom. = 17,027Ah/104 cells = 163.7Ah ..... that's around 1% better capacity in the same size cell ....... really, if that was the case, no one would use NMC chemistry cells would they.
Add to this the fact MG derated the battery capacity in later models to 49kwh and no doubt this figure is also inflated using 3.65v as the nom. cell voltage, using the equations above comes out to 129Ah per cell ..... I still doubt it is even that much ...... Many cell/battery manufacturers like to use the other myth that only 80% of the capacity can be used, so they add the other 20% to their cell/battery capacity claims .... use this on the 51kwh claim and what figure do you come up with .......

I just realised I posted all this in the start of this thread .... sorry about that folks

T1 Terry

No need to apologise, this is good info and makes more sense after the context of the additional posts.

So, your assertion is that the "actual" capacity of the LFP battery in the 51 is 41.6kWh, but the BMS has been programmed to expect 51kWh and is slowly adjusting downward over time to meet the real capacity of the battery?

Should it be possible to establish the "real" capacity of the battery by charging to 100% and then driving the car until it shuts down, then checking the used kWh via the trip meter?

 

[AlC]

...in which case the 51's SOH should level off (or stop dropping so precipitously) at 82% SoH right?

 

[hojnikb]

My guess is the steady loss of SoH is the real capacity catching up with the claimed capacity as far as the computer sees it. When it drops to 42Ah capacity, the degradation will slow to a much more realistic figure of less than 1% per yr.

The calculations I've made for the true 51 capacity are 104 cells X 125Ah X 3.2v nom. =41.6kwh.
The nom. LFP battery voltage is a solid known figure, the 104 cells is also a known figure. Working backwards 51,000wh/3.2v = 15397.5Ah/104 cells = 153.24Ah per cell.

Considering LFP isn't as energy dense as NMC, the same size battery box holds the same number of cells, 104, yet it is supposed to have a capacity of 63,000wh. 63000wh/3.7v nom. = 17,027Ah/104 cells = 163.7Ah ..... that's around 1% better capacity in the same size cell ....... really, if that was the case, no one would use NMC chemistry cells would they.
Add to this the fact MG derated the battery capacity in later models to 49kwh and no doubt this figure is also inflated using 3.65v as the nom. cell voltage, using the equations above comes out to 129Ah per cell ..... I still doubt it is even that much ...... Many cell/battery manufacturers like to use the other myth that only 80% of the capacity can be used, so they add the other 20% to their cell/battery capacity claims .... use this on the 51kwh claim and what figure do you come up with .......

I just realised I posted all this in the start of this thread .... sorry about that folks

T1 Terry

I highly doubt that the actual raw capacity is 41.6kWh. That's 10kWh less than advertised. Chinese are sneaky, but not that sneaky. First of all, this would make this car way more efficient than it actually is. Secondly, this would show in charging, as considering charging losses you'd never be able to come close to 51kWh+ AC power delivered.

And third thing; you're assuming that all NMC cells are of high density type. That does not have to be the case. Factory can design and manufacture cell of certain size and energy density, regardless of what is actually achievable. Good example of this are prismatic LFP cells you can buy yourself for DIY packs. They come in 280-320Ah (maybe even more?) in the same basic size.

And there's also 77kWh model, that i would assume uses the same size battery box.


So i'd guess (and that's just my guess). They likely fill the pack with 51kWh worth of LFP cells. With 77kWh likely do the same, but with higher density NMC cells and with 64kWh they might just be using lower density cells to hit that capacity. There's no info on 77kWh pack configuration, so that's just my speculation.

But pack being much smaller actually? That i don't buy.

 

[Tomg4]

My guess is the steady loss of SoH is the real capacity catching up with the claimed capacity as far as the computer sees it. When it drops to 42Ah capacity, the degradation will slow to a much more realistic figure of less than 1% per yr.

The calculations I've made for the true 51 capacity are 104 cells X 125Ah X 3.2v nom. =41.6kwh.
The nom. LFP battery voltage is a solid known figure, the 104 cells is also a known figure. Working backwards 51,000wh/3.2v = 15397.5Ah/104 cells = 153.24Ah per cell.

Considering LFP isn't as energy dense as NMC, the same size battery box holds the same number of cells, 104, yet it is supposed to have a capacity of 63,000wh. 63000wh/3.7v nom. = 17,027Ah/104 cells = 163.7Ah ..... that's around 1% better capacity in the same size cell ....... really, if that was the case, no one would use NMC chemistry cells would they.
Add to this the fact MG derated the battery capacity in later models to 49kwh and no doubt this figure is also inflated using 3.65v as the nom. cell voltage, using the equations above comes out to 129Ah per cell ..... I still doubt it is even that much ...... Many cell/battery manufacturers like to use the other myth that only 80% of the capacity can be used, so they add the other 20% to their cell/battery capacity claims .... use this on the 51kwh claim and what figure do you come up with .......

I just realised I posted all this in the start of this thread .... sorry about that folks

T1 Terry

I highly doubt that it is 'only' a ~42kWh battery pack. That's 20% less than advertised.
If that's the case than the MG4 would be MORE efficient than a Standard Range Tesla M3, which i CANNOT imagine
MG4 51kWh (or 42kWh as you say): WLTP range of 350 km, so 8,33km/kWh (350/42)
Tesla M3 Standard Range, 55kWh battery, WLTP range of 448, so 8,14 km/kWh.

 

[EVentropy]

Can't agree there Terry. AFAIK, nominal voltage is arbitary figure @~20%SOC for LFP.
And, as above, efficiency is bollocks.
Besides, why are Carscammer and VDS so different?

 

[tsedge]

Has anyone ever actually seen real-world battery degradation in a SR/LFP car?

I'm not talking about the meaninglessness of SOH, but real world?

Anyone done over 100,000 miles / 160,000 kms and had the discipline to compare range for the same journey over that lifetime?

(One reason I ask is we do have a report from a 100k LR/NMC taxi driver who states no noticeable battery degradation, and we know LFP should do better - of course age matters as well as miles).

 

[T1 Terry]

I highly doubt that the actual raw capacity is 41.6kWh. That's 10kWh less than advertised. Chinese are sneaky, but not that sneaky. First of all, this would make this car way more efficient than it actually is. Secondly, this would show in charging, as considering charging losses you'd never be able to come close to 51kWh+ AC power delivered.
OK, so what is the most anyone has recorded when recharging a 51 pack?

I highly doubt that it is 'only' a ~42kWh battery pack. That's 20% less than advertised.
If that's the case than the MG4 would be MORE efficient than a Standard Range Tesla M3, which i CANNOT imagine
MG4 51kWh (or 42kWh as you say): WLTP range of 350 km, so 8,33km/kWh (350/42)
Tesla M3 Standard Range, 55kWh battery, WLTP range of 448, so 8,14 km/kWh.
Why would they have revised the battery capacity down to 49kWh? I suspect it will continue to be revised in small steps, you wouldn't want to caught out telling bold faced porky pies would you?
The vehicle weight hasn't reduced, so they didn't fit smaller capacity cells to reduce weight and make it more efficient, yet the claimed efficiency range also continues.

As far as the WLTP range .... MG MG4 Electric 51 kWh says it's only 300km, not 350, that comes out to 7.14km/kWh doesn't it?
Still, it's a bit like solar panel claimed output ..... who gets that in the real world? How many Tesla owners will admit the claimed range of the std model is work of fiction?

T1 Terry

 

[T1 Terry]

No idea why that posted twice, so it's off in the ether providing more feed stock for future posts

T1 Terry

 

[EVentropy]

Actually I have always taken SOH with a grain of salt. My CALB cells capacity tested at 231 to 234Ah, so I set them at 230 so they should have read 100+%. Nope, 95%. And they are still at 95% three years later! Balmar BMS. Never took a shine to Balmar stuff , except for their voltage regulators which had the bells and whistles way before the opposition.

 

[Tomg4]

I highly doubt that the actual raw capacity is 41.6kWh. That's 10kWh less than advertised. Chinese are sneaky, but not that sneaky. First of all, this would make this car way more efficient than it actually is. Secondly, this would show in charging, as considering charging losses you'd never be able to come close to 51kWh+ AC power delivered.
OK, so what is the most anyone has recorded when recharging a 51 pack?

I highly doubt that it is 'only' a ~42kWh battery pack. That's 20% less than advertised.
If that's the case than the MG4 would be MORE efficient than a Standard Range Tesla M3, which i CANNOT imagine
MG4 51kWh (or 42kWh as you say): WLTP range of 350 km, so 8,33km/kWh (350/42)
Tesla M3 Standard Range, 55kWh battery, WLTP range of 448, so 8,14 km/kWH
Why would they have revised the battery capacity down to 49kwh? I suspect it will continue to be revised in small steps, you wouldn't want to caught out telling bold faced porky pies would you?
The vehicle weight hasn't reduced, so they didn't fit smaller capacity cells to reduce weight and make it more efficient, yet the claimed efficiency range also continues.

As far as the WLTP range .... MG MG4 Electric 51 kWh says it's only 300km, not 350, that comes out to 7.14km/kwh doesn't it?
Still, it's a bit like solar panel claimed output ..... who gets that in the real world? How many Tesla owners will admit the claimed range of the std model is work of fiction?

T1 Terry

It literally states 350km:

WLTP Ratings​

Range	350 km
Rated Consumption	170 Wh/km
Vehicle Consumption	145 Wh/km

Your calculations are based on some assumptions, I really don't believe the battery pack is ~42kWh. That's a massive fraud and would be enough to start a big consumer lawsuit

 

[Semerkand]

3 - 4% degradation per yr only occurs if the battery is held at 100% SOC for that period of time ....

Could this explain why the first owner of my car lost SOH around 6%?

when i bought the car
Soh:93.64%
10500 km

now(3 months later):
Soh:92.9%
21500 km

(SOH values were checked after a 100% balancing charge from a low percentage. I don't know how accurate it is.)

And is the 41.6 kWh value the value that will settle over time?
I would also like to state that I loaded 40.7 kWh energy from 3% to 83% last night. I also remember loading 45-46 kWh for balancing.

 

[hojnikb]

Can't agree there Terry. AFAIK, nominal voltage is arbitary figure @~20%SOC for LFP.
And, as above, efficiency is bollocks.
Besides, why are Carscammer and VDS so different?

Nominal voltage is not an "arbitrary" figure. It's actually an average voltage you get, if you divide Wh(energy) by Ah(capacity). For example, a 280Ah LFP cell has 896Wh of energy, so 896/280 comes out to 3.2V.