MG4 51kWh LFP Battery Health

decrep said:

I like the bang crunch concept, but it seems to be out of favour at the moment.

Click to expand...

Too much Dark Energy? Or the god bothers won't allow it

T1 Terry

whatever it is, it isn't understood very well, so I'm still in favour of bang crunch, but only on an intuitional level. It just feels right.

Back on the 51 SOH, my theory about the true battery capacity ......

We arrived at The Royal Adelaide Hospital with 10% remaining battery and 2,000km on the clock, so we plugged into a Chargefox DC fast charger, this the invoice that was emailed to us


Quick math calculation, from 10% to 100% would require 90% of the capacity to be replaced, 37.83kWh. 90% x 1.1 =99.99% 37.83 x 1.11 = 41.99kWh ..... just saying.

T1 Terry

T1 Terry said:

Back on the 51 SOH, my theory about the true battery capacity ......

We arrived at The Royal Adelaide Hospital with 10% remaining battery and 2,000km on the clock, so we plugged into a Chargefox DC fast charger, this the invoice that was emailed to us
View attachment 35102

Quick math calculation, from 10% to 100% would require 90% of the capacity to be replaced, 37.83kWh. 90% x 1.1 =99.99% 37.83 x 1.11 = 41.99kWh ..... just saying.

T1 Terry

Click to expand...

You're still convienced that pack is only ~40 something usable?

The pack has 104 cells and 379,6V maximum voltage. Each cell is rated at 156Ah nominal. Nominal voltage is stated as 327V.

327Ah*104v is exactly 51.012kWh, just as they advertised. And difference between 51.012kWh and 50,8kWh is the tiny top buffer it has, which also explains why this car has basically no regen at full.

the pack also weighs 398.7Kg, so that makes pack 128Wh/kg, right in line with typical automotive LFP packs.




I think the whole issue in your case is that you take SoC way to seriously. LFPs have notoriously inaccurate SoC, if you don't regularly balance and 5-100% cycle the battery. And there's also the whole unknown of charge efficiency (which can vary depending on many factors). All of that can add up.

If the car really only had ~42kWh usable, it would be the most efficient car in its class by far.

My SE SR had a SOH of 97% according to the dealer at its 45,000 mile service, car registered November 22.

Love the very off topic discussion about the universe BTW

Tight Git said:

My SE SR had a SOH of 97% according to the dealer at its 45,000 mile service, car registered November 22.

Love the very off topic discussion about the universe BTW

Click to expand...

What year is yours? That's a very low degradation for sure!

There's also one interesting thing; they rate their pack nominal at 327V, which is 3.144V nominal per cell. The usual value for LFP cells is around 3.2V.

Plugging the math using this value makes the pack closer to 52kWh (51.916kWh to be exact). Maybe that's their top spare buffer?

On the subject of the health of the 51 LFP battery, something that keeps me awake at night when I've run out of other things to worry about is when I should charge my infrequently driven car to 100%.

I know you're supposed to regularly charge the LFP to 100% to prevent BMS drift, and I know people used to say LFPs are fine being at 100%, but now the advice I've seen is you don't want to leave LFPs at a high SoC for long periods.

My car gets driven only on weekends. I've had it for a year and a half and it still has less than 6,000km on the clock.

So when I do charge it to 100%, it'll often be a week or more before I can get it down under 80%. I'll then wait until it's at about 30% (which takes weeks) before charging it up to 100% again.

Am I damaging the battery? Should I perhaps charge to only 80% with the occasional 100% before long trips?

T1 Terry said:

I guess you have all seen the reports that EV batteries are outlasting the lab test results that often gave a very short cycle life/kms travelled/age expectations, LFP have a better cycle life than NMC or any of the cobalt/lithium compounds, so treated correctly, they have a very long cycle/calander life.

Click to expand...

Yes, but even based on lab test result the NMC cells in my MG4 will outlive the car.

hojnikb said:

You're still convienced that pack is only ~40 something usable?

The pack has 104 cells and 379,6V maximum voltage. Each cell is rated at 156Ah nominal. Nominal voltage is stated as 327V.

327Ah*104v is exactly 51.012kWh, just as they advertised. And difference between 51.012 and 50,800 is the tiny top buffer it has, which also explains why this car has basically no regen at full.

the pack also weighs 398.7Kg, so that makes pack 128Wh/kg, right in line with typical automotive packs.

View attachment 35104


I think the whole issue in your case is that you take SOC way to seriously. LFPs have notoriously inaccurate SOC, if you don't regularly balance and 5-100% cycle the battery. And there's also the whole inknown of charge efficiency (which can vary depending on many factors). All of that can add up.

If the car really only had ~42kWh usable, it would be the most efficient car in its class by far.

Click to expand...

LFP cells have a very reliable SOC, you just need to know how to measure it.

The battery isn't very old, but has been cycled and slow charged each time, so there just isn't any more room to store any added electrical energy.

As far as efficiency, how far do you get out of your 51kwh battery? At 10% remaining the guess-a-meter was dropping around 2km range every 1 km travelled in 60km/h traffic .... a fairly good sign there was bugger all left.

If you have much experience with LFP cells, you would know that the remaining energy after 3v per cell no load and 2.5v under load, isn't a whole lot, yet they measure the 51kwh down to 2.5v per cell .... and the chances of all 104 cells being perfectly balanced at 2.5v under load, especially when top balancing is used ...... is about as close to zero as you'll get .....

You will also be familiar with the energy density difference between LFP cells and NMC cells, yet they get 104 of each type of cell into that battery case. There is only 13.5Ah between the capacity of the NMC cells and the LFP cells, they certainly packed a lot of Ah into a small case with the LFP cells .....

No idea how you are using the weight comparison of the battery pack, but there is only 9.9kg difference in weight between the same number of LFP cells as NMC cells .... that weight is not just the cells, but the whole BMS, cooling system and case add in ......

I think the figures advertised are reverse calculations, start with the end figure you want, 51kwh, divide that by the number of cells, 104, that is a fixed number, then by the nom. voltage for LFP cells, that is a known hard fact 3.2v .... what is left is the Ah you need to claim each cell holds ... the maths comes out to 153Ah, so their maths isn't real good either .....

Until someone strips out a 51 LFP battery pack, I'm guess we are all guessing as to just how much the true capacity is ....... well, until the battery health bottoms out at around 90% mark and then stops falling at such a rapid rate .......

T1 Terry

AlC said:

On the subject of the health of the 51 LFP battery, something that keeps me awake at night when I've run out of other things to worry about is when I should charge my infrequently driven car to 100%.

I know you're supposed to regularly charge the LFP to 100% to prevent BMS drift, and I know people used to say LFPs are fine being at 100%, but now the advice I've seen is you don't want to leave LFPs at a high SoC for long periods.

My car gets driven only on weekends. I've had it for a year and a half and it still has less than 6,000km on the clock.

So when I do charge it to 100%, it'll often be a week or more before I can get it down under 80%. I'll then wait until it's at about 30% (which takes weeks) before charging it up to 100% again.

Am I damaging the battery? Should I perhaps charge to only 80% with the occasional 100% before long trips?

Click to expand...

I wouldn’t worry about it too much mate, but charging to 80% probably won’t hurt and it seems to serve you fine to not have 100% in the battery pack.

Also, high battery health might not be so important if you only do about 4000km a year. But only you can answer that for yourself

T1 Terry said:

Are you sure these are LFP cells and not NMC cells? That is more like an NMC cell degradation plot, or it is adjusting the real capacity

Click to expand...

Yes, my car has 51kWh of LFP cells. I'm not saying that the chart shows the actual degradation. It is however what the BMS reports via OBD2. Every single day the car gets turned on the countdown timer continues.

I am currently following the instructions I got above: drive until SOC is well below 10%, then do a 100% charge. See if that triggers an update to SOH based on an actual measurement by the BMS.

Hopefully it triggers a balance at the end too. Although I have my doubts my car ever did a cell balance. I just went back in my records, even the very recording of charging the car to 100% did not have a balance at end. It did however keep going at 9A AC for about 17 minutes after it showed 100% SOC (at 7:17). So SOC was out, and was corrected.

Peter WA said:

Yes, my car has 51kWh of LFP cells. I'm not saying that the chart shows the actual degradation. It is however what the BMS reports via OBD2. Every single day the car gets turned on the countdown timer continues.

I am currently following the instructions I got above: drive until SOC is well below 10%, then do a 100% charge. See if that triggers an update to SOH based on an actual measurement by the BMS.

Hopefully it triggers a balance at the end too. Although I have my doubts my car ever did a cell balance. I just went back in my records, even the very recording of charging the car to 100% did not have a balance at end. It did however keep going at 9A AC for about 17 minutes after it showed 100% SOC (at 7:17). So SOC was out, and was corrected.


View attachment 35112

Click to expand...

It will be interesting to see if the degradation of battery health bottoms out in the high 80% area, with occasional trips back up to the 90% region.

As a general rule, I've found LFP cells don't lose capacity when treated well, that doesn't mean treating them with kid gloves, they like to work, they don't like being taken out of their "safe for long life" voltage range when charging or discharging ... it isn't the rested voltage like lead acid batteries, the 2.8v threshold should be exceeded too often while under load and the 3.6v while charging, so a very fast charge needs to throttle back as the cell approaches the 3.6v mark.

The degradation that comes with cycle use, is the internal resistance and this will start to limit the high current draw under load because the cell voltage drops, yet when the load is reduced, the voltage returns well into the safe range, the capacity is still there at that stage, it just can't be supplied at the high rate an EV needs. At this point, they still have many yrs service life as a house battery, because the high loads are much lower in a house battery system than in an EV.
As an example:
A 100Ah cell will reach a point where it can no longer deliver the whole 100 amps for 1 hr without the voltage dropping outside the safe zone, yet it will still deliver 50 amps for 2 hrs and maintain better than 3v while doing it.

T1 Terry

I'm clearly getting too old for this, it dawned on me while finishing that post to Peter in WA.

Battery capacity is measured at a fixed load over time. If you are unrealistic about the assumed load the battery will be operating at and substituted with a lighter load, the battery will deliver a greater number of Ah over a given time before the cell voltages drop below the level the test is terminated.

As an example, this is the graph for a 100Ah Winston LFP cell ..... bugga, they were all on the computer and back ups that were lost in the fire, so I can't show you the graphs that explain what I'm saying ....
This is the graph for a Winston LYP 100Ah cell, not a great example because LYP cells have a better high discharge rate than LFP cells.

OK, I'm going to market this cell as 120Ah. If I load test it at 0.25CA, or 25 amps over 4 hrs and continued the load until the voltage dropped to 2.5v. With a bit of imagination, you can see the discharge curve is better that the 0.5CA discharge curve (50 amps over 2 hrs)

The problem is, I'm going to use this battery at a 3CA discharge rate (300 amps over 20 mins)
At the load rate the battery will be used, 3CA, it is not a 120Ah battery, brand new it is a 100Ah battery.



The paperwork shows the MG4 51kwh battery is built from 104 x 156Ah cells .... but was that 156Ah measured at 3CA, the motor is 150kw after all. Or was the 156Ah measured using the lead acid deep cycle battery load rate of C20, the capacity divided by 20, 7.8 amps, over a 20 hr period till the cell voltage drops to 2.5v .... It can still be advertised as a 156Ah cell ......

T1 Terry

T1 Terry said:

LFP cells have a very reliable SOC, you just need to know how to measure it.

The battery isn't very old, but has been cycled and slow charged each time, so there just isn't any more room to store any added electrical energy.

As far as efficiency, how far do you get out of your 51kwh battery? At 10% remaining the guess-a-meter was dropping around 2km range every 1 km travelled in 60km/h traffic .... a fairly good sign there was bugger all left.

If you have much experience with LFP cells, you would know that the remaining energy after 3v per cell no load and 2.5v under load, isn't a whole lot, yet they measure the 51kwh down to 2.5v per cell .... and the chances of all 104 cells being perfectly balanced at 2.5v under load, especially when top balancing is used ...... is about as close to zero as you'll get .....

You will also be familiar with the energy density difference between LFP cells and NMC cells, yet they get 104 of each type of cell into that battery case. There is only 13.5Ah between the capacity of the NMC cells and the LFP cells, they certainly packed a lot of Ah into a small case with the LFP cells .....

No idea how you are using the weight comparison of the battery pack, but there is only 9.9kg difference in weight between the same number of LFP cells as NMC cells .... that weight is not just the cells, but the whole BMS, cooling system and case add in ......

I think the figures advertised are reverse calculations, start with the end figure you want, 51kwh, divide that by the number of cells, 104, that is a fixed number, then by the nom. voltage for LFP cells, that is a known hard fact 3.2v .... what is left is the Ah you need to claim each cell holds ... the maths comes out to 153Ah, so their maths isn't real good either .....

Until someone strips out a 51 LFP battery pack, I'm guess we are all guessing as to just how much the true capacity is ....... well, until the battery health bottoms out at around 90% mark and then stops falling at such a rapid rate .......

T1 Terry

Click to expand...

I'm very familiar with LFP pack. And there's a reason why these cars don't allow setting max SoC. If people set the maximum SoC at 70-80%, GOM would become wildly inaccurate.

The issue with LFP is it's very flat volage curve within 10-90% of SoC. This is why it's so difficult to determine actual SoC. NCA/NMC has a much more linear curve and as such much easier to determine SoC and doesn't need as much 5-100% cycles. This is why they can get away with setting max charge state without ill effect on SoC accuracy.

you would know that the remaining energy after 3v per cell no load and 2.5v under load, isn't a whole lot, yet they measure the 51kwh down to 2.5v per cell

Click to expand...

Doesn't really matter. As long as BMS is accuratly calibrated, it will show correct SoC. But if people don't regularly cycle 5-100%, of course it will drift away and inaccuracies will happen, especailly down bellow.

You will also be familiar with the energy density difference between LFP cells and NMC cells, yet they get 104 of each type of cell into that battery case. There is only 13.5Ah between the capacity of the NMC cells and the LFP cells, they certainly packed a lot of Ah into a small case with

Click to expand...

If anything, they use low density NMC cells. If they used highly dense NMC cells, a 77kWh pack could not exist within the same formfactor and configuration. You can have varying densities within the same size of cell. And that can also be beneficial, as those kinds of cells tend to have higher cycle life.
Just look at 18650 cells. You can get them all the way down to 1500mAh or 3500mAh. Stand to reason, that automotive packs can be the same way.

Until someone strips out a 51 LFP battery pack, I'm guess we are all guessing as to just how much the true capacity is ....... well, until the battery health bottoms out at around 90% mark and then stops falling at such a rapid rate .......

Click to expand...

The capacity surely is correct. It's how SoH is calculated and how much buffers there are top and bottom are somewhat of a mistery.
There's just no way they be lying about capacity for 10-20% as you state above.

T1 Terry said:

I'm clearly getting too old for this, it dawned on me while finishing that post to Peter in WA.

Battery capacity is measured at a fixed load over time. If you are unrealistic about the assumed load the battery will be operating at and substituted with a lighter load, the battery will deliver a greater number of Ah over a given time before the cell voltages drop below the level the test is terminated.

As an example, this is the graph for a 100Ah Winston LFP cell ..... bugga, they were all on the computer and back ups that were lost in the fire, so I can't show you the graphs that explain what I'm saying ....
This is the graph for a Winston LYP 100Ah cell, not a great example because LYP cells have a better high discharge rate than LFP cells.

OK, I'm going to market this cell as 120Ah. If I load test it at 0.25CA, or 25 amps over 4 hrs and continued the load until the voltage dropped to 2.5v. With a bit of imagination, you can see the discharge curve is better that the 0.5CA discharge curve (50 amps over 2 hrs)

The problem is, I'm going to use this battery at a 3CA discharge rate (300 amps over 20 mins)
At the load rate the battery will be used, 3CA, it is not a 120Ah battery, brand new it is a 100Ah battery.

View attachment 35114

The paperwork shows the MG4 51kwh battery is built from 104 x 156Ah cells .... but was that 156Ah measured at 3CA, the motor is 150kw after all. Or was the 156Ah measured using the lead acid deep cycle battery load rate of C20, the capacity divided by 20, 7.8 amps, over a 20 hr period till the cell voltage drops to 2.5v .... It can still be advertised as a 156Ah cell ......

T1 Terry

Click to expand...

51kWh motor is 125kW peak (so basically it can deliver that power for about 30secs). Continuous power is 54kW.

So if you plan on capacity testing with driving, 125kW discharge rate is not the rate you'll be discharging the battery from 100 to 0%, as motor will derate itself very quickly.
Most ESS cells are designed with 0,5-1C discharge and charge rates in mind. With 117kW charging on the 51kWh version, the cells need to be rated for at least 2.5C charge rate, way above what most normal ESS versions are rated for.

54kW with some motor/inverer losses and aux drains comes to just over 1C. And that's the discharge rate, that most cells are capacity rated at.

In reality, avarage power will be closer to something like 15-20kW, which helps cells easily hit their rated capacity.

And lets not forget; those are not stationary LFP cells, but automotive. Stands to reason their caracteristcs are a bit different and designed with higher charge(!!) and discharge rates in mind.





These looks like the sort of cells that SAIC might be using. Dimensions look about right (they claim pack is 110mm thick) but their characteristics don't seem quite right.

In any case, i have a strong suspision that SAIC might be using the actual capacity of the cells (not rated) to have some degradation buffer. You see, typically a 156Ah isn't 156Ah from the factory, but usually at least 5-10% more.

So lets assume that 156Ah cell has typically 164Ah of actual usable capacity when new. SAIC could be using that difference for their buffer, while still being correct about their advertised capacity.

So 51kWh nominal and 53.63kWh raw "usable" and the difference is used as a degradation buffer. Might also explain why rated pack voltage per cell is only 3.144V instead of the usual 3.2V.

T1 Terry said:

Quick math calculation, from 10% to 100% would require 90% of the capacity to be replaced, 37.83kWh. 90% x 1.1 =99.99% 37.83 x 1.11 = 41.99kWh ..... just saying.

Click to expand...

would you mind explaining your calculation to me as i dont understand how you arrived at 41.99
what is 1.1 and 1.11?
what does 99.99% represent?

Surely DC charging losses are minimal?
37.83kWh for 90% charge sounds too little IMO

just intrested

hojnikb said:

With 117kW charging on the 51kWh version

Click to expand...

Not sure about over there but here the 51 kWh LFP MG4 has a max DC charge rate of 88 kW.

AlC said:

On the subject of the health of the 51 LFP battery, something that keeps me awake at night when I've run out of other things to worry about is when I should charge my infrequently driven car to 100%.

I know you're supposed to regularly charge the LFP to 100% to prevent BMS drift, and I know people used to say LFPs are fine being at 100%, but now the advice I've seen is you don't want to leave LFPs at a high SoC for long periods.

My car gets driven only on weekends. I've had it for a year and a half and it still has less than 6,000km on the clock.

So when I do charge it to 100%, it'll often be a week or more before I can get it down under 80%. I'll then wait until it's at about 30% (which takes weeks) before charging it up to 100% again.

Am I damaging the battery? Should I perhaps charge to only 80% with the occasional 100% before long trips?

Click to expand...

What I tend to do is to let the car sit at whatever SOC I arrived home at, until the evening before I want it again. Then I charge it up to 100% the night before it's going to be driven. The exception is that if I get back very low then I'll only give it as much as I can get at off-peak rates, which will take it up to maybe 80%. I'll leave it there until the evening before I next want it, and do the last bit of charge and balance then. That means that if I need the car unexpectedly it will always have something in it no matter what.

T1 Terry said:

Apologies for the long post, feel free to skip over it if you have no interest in understanding how LFP cells die an early death

Bypassed the BMS allowing some of the cells to discharge to 0v, then put a battery charger on the whole battery at higher than an amp or so until the low cells reached above 3v .... and often reset the system by pressing the momentary relay latching switch as soon as the voltage is high enough to hold the contactor closed, and full solar and inverter charging also slammed into the cells ....... Then often leaving a dumb transformer type charger on the battery resulting in cell hitting 4.5v ..... all of these things will murder an LFP cell.

The over voltage charging on its own just increases the internal resistance, so when a cell reaches 3.6v, the charger is programmed to drop into float mode, but with the high internal resistance adds up to 0.5v to the actual cell internal voltage when charging and drops the voltage by the same amount when discharging ..... so the cell that cut off the charging @ 3.6v was actually only at 3.1v, then a load is applied and the voltage seen at the terminals is 2.6v ... and the BMS again isolates the battery ..... so they turn the bypass on again and yet another low voltage drain

Charging rapidly with the cell voltage below 1v will result in lithium actually transferring onto the graphite plate ... and that spot is always the spot where anything will attach to .... till it passes through the separator material and shorts out that plate in the cell ....
or
The rubbish that separates from the electrolyte coats the graphite material until no lithium ions can penetrate .... this results in the terminal voltage climbing rapidly till it trips the BMS, or gets that hot it boils off the electrolyte ..... No electrolyte, no method of transferring lithium ions from the active plate to the graphite plates ... so zero capacity, the same terminal voltage rapid climb and drop to 0v as a load is applied

T1 Terry

Click to expand...

OK, thanks for that!

AlC said:

On the subject of the health of the 51 LFP battery, something that keeps me awake at night when I've run out of other things to worry about is when I should charge my infrequently driven car to 100%.

I know you're supposed to regularly charge the LFP to 100% to prevent BMS drift, and I know people used to say LFPs are fine being at 100%, but now the advice I've seen is you don't want to leave LFPs at a high SoC for long periods.

My car gets driven only on weekends. I've had it for a year and a half and it still has less than 6,000km on the clock.

So when I do charge it to 100%, it'll often be a week or more before I can get it down under 80%. I'll then wait until it's at about 30% (which takes weeks) before charging it up to 100% again.

Am I damaging the battery? Should I perhaps charge to only 80% with the occasional 100% before long trips?

Click to expand...

my mileage is pretty low so bounce charging between 40-80% usually ie charge to 80% when it gets below 40%. Charge to 100% night before i do a long run or every month or two

gdog said:

would you mind explaining your calculation to me as i dont understand how you arrived at 41.99
what is 1.1 and 1.11?
what does 99.99% represent?

Surely DC charging losses are minimal?
37.83kWh for 90% charge sounds too little IMO

just intrested

Click to expand...

OK, if 90% of the battery capacity was the amount added to the battery to bring it up from 10% to 100%, then that value represents 100% of the energy added. To get from 90% to 100%, 0.1 would equal 9% so multiplying the 90% by 1.1 adds 9% to the 90% = 99%. Add 0.01 of 90% = 0.9%. 90% x 1.11 = 99%

T1 Terry

hojnikb said:

[Hot Item] Catl 3.2V 156ah LiFePO4 Battery Suitable for Fishing Boats, Electric Vehicles, RV, Car Power Storage Energy

Type: LiFePO4 Usage: UPS, Electric Power, Electric Bicycle Nominal Voltage: 3.2V Discharge Rate: High Discharge Rate Shape: Cylindrical Battery Electrolyte: LiFePO4

linksunhk.en.made-in-china.com

View attachment 35117

These looks like the sort of cells that SAIC might be using. Dimensions look about right (they claim pack is 110mm thick) but their characteristics don't seem quite right.

In any case, i have a strong suspision that SAIC might be using the actual capacity of the cells (not rated) to have some degradation buffer. You see, typically a 156Ah isn't 156Ah from the factory, but usually at least 5-10% more.

So lets assume that 156Ah cell has typically 164Ah of actual usable capacity when new. SAIC could be using that difference for their buffer, while still being correct about their advertised capacity.

So 51kWh nominal and 53.63kWh raw "usable" and the difference is used as a degradation buffer. Might also explain why rated pack voltage per cell is only 3.144V instead of the usual 3.2V.

Click to expand...

You do realise they are C grade 200Ah cells at best. Did you look at the temp v charge rate profile, a very narrow window for recharging as well, so C grade might be a tad optimistic.
The fact CATL don't sell to the public and all A grade cells are consumed by the electric car manufacturers, these cells are from the trash can, cells that failed CATL quality testing so were rejected.
Most quality lithium battery manufacturers don't sell their rejects, but rather recycle them, ensuring their name is not connected with anything not top quality.
I'm guessing someone has bought these cells from a recycler and are using the CATL brand name without their permission, an enquiry with CATL using the barcode on top of the label will confirm or deny what I'm suggesting.
Do you really think MG would use C grade cells that they are attaching a 10yr warranty saying they will replace them if they fall below 70% capacity in that 10 yr period? And members here are questioning if MG would distort the capacity of their battery pack

T1 Terry

In any case, i have a strong suspision that SAIC might be using the actual capacity of the cells (not rated) to have some degradation buffer. You see, typically a 156Ah isn't 156Ah from the factory, but usually at least 5-10% more.

So lets assume that 156Ah cell has typically 164Ah of actual usable capacity when new. SAIC could be using that difference for their buffer, while still being correct about their advertised capacity.

Click to expand...

They are some dark tinted rose coloured glasses you are wearing, are you sure you don't work for SAIC in the PR dept
Do really expect anyone to believe a Chinese EV manufacturer would derate the battery capacity to add a buffer? That would mean their 10 yr warranty on the battery is actually factoring in a 60% degradation, the 10% "buffer" plus the 30% degradation from the claimed 51kwh .... so my new MG4 51 would actually have 164Ah x 104 cells x 3.2v nom. = 54.6kwh battery? If that is the case, the 102km trip from home to the hospital, with a big down hill into Adelaide adding some regen to the capacity, used 49.1 kwh hrs of battery capacity ...... I hope you are wrong and I'm closer to the real situation, if the capacity is going to drop even 10% in the short term, I'll need a recharge part way so I can get to the big down hill run, then recharge to get back to the mid way charging point so I can get back home to do a 200km round trip .....

T1 Terry

wattmatters said:

Not sure about over there but here the 51 kWh LFP MG4 has a max DC charge rate of 88 kW.

Click to expand...

EU spec versions up to the "mild" facelift are rated for 117kW.

T1 Terry said:

You do realise they are C grade 200Ah cells at best. Did you look at the temp v charge rate profile, a very narrow window for recharging as well, so C grade might be a tad optimistic.
The fact CATL don't sell to the public and all A grade cells are consumed by the electric car manufacturers, these cells are from the trash can, cells that failed CATL quality testing so were rejected.
Most quality lithium battery manufacturers don't sell their rejects, but rather recycle them, ensuring their name is not connected with anything not top quality.
I'm guessing someone has bought these cells from a recycler and are using the CATL brand name without their permission, an enquiry with CATL using the barcode on top of the label will confirm or deny what I'm suggesting.
Do you really think MG would use C grade cells that they are attaching a 10yr warranty saying they will replace them if they fall below 70% capacity in that 10 yr period? And members here are questioning if MG would distort the capacity of their battery pack

T1 Terry

Click to expand...

I'm not saying these exact cells are in the MG4.. Just these "sort" of cells..

T1 Terry said:

They are some dark tinted rose coloured glasses you are wearing, are you sure you don't work for SAIC in the PR dept
Do really expect anyone to believe a Chinese EV manufacturer would derate the battery capacity to add a buffer? That would mean their 10 yr warranty on the battery is actually factoring in a 60% degradation, the 10% "buffer" plus the 30% degradation from the claimed 51kwh .... so my new MG4 51 would actually have 164Ah x 104 cells x 3.2v nom. = 54.6kwh battery? If that is the case, the 102km trip from home to the hospital, with a big down hill into Adelaide adding some regen to the capacity, used 49.1 kwh hrs of battery capacity ...... I hope you are wrong and I'm closer to the real situation, if the capacity is going to drop even 10% in the short term, I'll need a recharge part way so I can get to the big down hill run, then recharge to get back to the mid way charging point so I can get back home to do a 200km round trip .....

T1 Terry

Click to expand...

It's certanly more plausible than them selling a battery that has actual capacity 10-20% lower than advertised. After all, MG4 is an export model and fooling overseas customers about something so essential like battery capacity just isn't on the table -- even for Chinese.

But fact of the matter is, battery manufacturing has variances, even high quality automotive cells. And typically, A tier manufacturer will rate their cells with the worst capacity that that series of cells is capable of.

This is true of any products that use lithium batteries. Look at phones, smartwatches, laptops etc.. Their cells usually have at two ratings; typical and minimum. And most often than not, a factory cell capacity will always be above typical.

iPhones for example use minimum capacity as their base 100% SoH. So an iphone with minimum rated capacity 2000mAh and 2050 typical capacity will likely have an actual capacity of ~2100mAh+ from the factory, but internal calculation will still show 100%. Only when capacity drops below 2000mAh, SoH starts dropping.

Comparing an EV battery with a watch or phone battery, really? The Chinese are the masters of double speak, remain ambiguous by hiding behind language misinterpretations barriers ...... but that is a one way street. Having friend who is in direct business relations with the son of a major Chinese province, opens doors and also opens the eyes on the Chinese way of avoiding the truth, he is able to ask the number 1 son what is really meant from what was communicated, they are two very different things and it is the way some things are worded that makes all the difference.
The obvious double speak is put out as a decoy, you think you have spotted the ambiguity in what was said, the underlying word play is the part that comes back to bite you, simply because you didn't see the facts in what they said because it was hidden ... there in plain sight, if you knew what to look out for, but worded in a way that looked like what you wanted to see.

As an example, can you spot the double speak and implied message that is not actually stated anywhere? This is not a promotion or attack on this reseller, it is just an example
12V 100Ah LiFePO4 Deep Cycle Lithium ion Phosphate Battery 4WD RV Camping Marine | eBay

T1 Terry