MG fully charged voltage

Label on car battery (sorry it's dirty)

IMG_20210109_214053703.jpg
 
Nominal voltage on battery 394.2 divided by nominal voltage on cells 3.65 = 108

I'll stop posting now haha, anyone please feel free to correct me, but it does look as though these are the cells used in our cars.
 
Chrisb said:
Nominal voltage on battery 394.2 divided by nominal voltage on cells 3.65 = 108

I'll stop posting now haha, anyone please feel free to correct me, but it does look as though these are the cells used in our cars.
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Looks right to me. Also, if we do end up seeing a terminal voltage of 450v rather than about 455v after the last update, I really don't think we need to be worrying.

They appear to have decided to drop the cell voltage from about 4.2v to 4.16\17v. This will be good for longevity of the battery. As for range, if you study a typical charge curve for this chemistry, the difference between 4.2v and 4.17v from a range point of view is measured more in yards than miles!

If anyone would like to prove it who is running the older BMS software with the finishing 455v or so. Please go and drive 1 mile. I'll be willing to bet before you've got to a mile, the voltage will be at 450v or lower. ;)
 
I don't know what type of cells the Mg5 uses, they may be totally different?

If the look at chart with the cells on the Max cell charge can actually be as high as 4.25v per cell, but yes 4.21 per cell is a bit high, doesn't exceed the specs of the cell though, but it may be the reason with the latest update that they're now charged to 4.16 per cell, as that will help as you've shown with battery lifespan. Maybe mg have looked back at data from cars over here and seen them degrading too quickly when charged at 4.21 per cell constantly and decided to lower it? I wonder if in other markets where the have the app etc whether they can set it to charge up to 80% on a regular basis or 100% for a long journey, a bit like Tesla/nissan, whereas ours was probably the first market where they charge up to 100% all the time?
 
Another thing which actually matches up with these cells possibly being in our cars is the charge rate, in the table it shows a max charge rate of 1.5c so that means 1.5 it's capacity, so if it is 50kw fully charged that's a 75 kw max charge rate, which I do believe sometimes we can get (weather/temperature dependent), but also that it's normal charge rate is 1c which is 50kw which is probably more the norm in good weather.
 
Here is the description of the CATL cells I posted earlier, interesting to read about the number of full cycles and battery life in years (7 years with losses, hmm isn't that the warranty).
Screenshot_20210128-111906.png
 
Paulie68 said:
Looks right to me. Also, if we do end up seeing a terminal voltage of 450v rather than about 455v after the last update, I really don't think we need to be worrying.

They appear to have decided to drop the cell voltage from about 4.2v to 4.16\17v. This will be good for longevity of the battery. As for range, if you study a typical charge curve for this chemistry, the difference between 4.2v and 4.17v from a range point of view is measured more in yards than miles!

If anyone would like to prove it who is running the older BMS software with the finishing 455v or so. Please go and drive 1 mile. I'll be willing to bet before you've got to a mile, the voltage will be at 450v or lower. ;)
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I tried this today, charged and balanced up to 455v, drove until it went to 450v and got 6.5 miles.
 
It did 3.3 miles per kw, it was only around town, so you could say it's about 2kw worth.
 
Chrisb said:
It did 3.3 miles per kw, it was only around town, so you could say it's about 2kw worth.
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So about 5% of capacity. There shouldn't be that much energy with this chemistry between 4.16v & 4.2v per cell. I'm wondering how accurate the voltage reading is now...

I'm looking forward to doing a full discharge to see what range I'm actually getting now and how it compares to the reported miles per kWh so I can see what the useable capacity is.
 
Paulie68 said:
So about 5% of capacity. There shouldn't be that much energy with this chemistry between 4.16v & 4.2v per cell. I'm wondering how accurate the voltage reading is now...

I'm looking forward to doing a full discharge to see what range I'm actually getting now and how it compares to the reported miles per kWh so I can see what the useable capacity is.
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So have you had the latest BMS update?
 
Paulie68 said:
So about 5% of capacity. There shouldn't be that much energy with this chemistry between 4.16v & 4.2v per cell. I'm wondering how accurate the voltage reading is now...

I'm looking forward to doing a full discharge to see what range I'm actually getting now and how it compares to the reported miles per kWh so I can see what the useable capacity is.
Click to expand...
Sounds very complicated.
 
Paulie68 said:
So about 5% of capacity. There shouldn't be that much energy with this chemistry between 4.16v & 4.2v per cell. I'm wondering how accurate the voltage reading is now...

I'm looking forward to doing a full discharge to see what range I'm actually getting now and how it compares to the reported miles per kWh so I can see what the useable capacity is.
Click to expand...
I’m far from an expert on lithium-ion batteries , however my observations are that when showing 100% charged they can show this % for quite a while until it drops in normal use. For example my Apple iPad shows 100% after a charge - I can use it for quite a while - say 20mins and it will still show 100% before it eventually starts to drop. Is it not also that EV‘s produce more power when their batteries are fully charged than when say 25% charged? At the other end of charge (when low on charge) the battery seems to reduce at a greater rate. It’s the reverse of charging - faster from low charge, slowly reducing as the battery becomes quite full - to a trickle to finish off. I’m not sure what all this means but it’s interesting.
 
Cocijo said:
I’m far from an expert on lithium-ion batteries , however my observations are that when showing 100% charged they can show this % for quite a while until it drops in normal use. For example my Apple iPad shows 100% after a charge - I can use it for quite a while - say 20mins and it will still show 100% before it eventually starts to drop. Is it not also that EV‘s produce more power when their batteries are fully charged than when say 25% charged? At the other end of charge (when low on charge) the battery seems to reduce at a greater rate. It’s the reverse of charging - faster from low charge, slowly reducing as the battery becomes quite full - to a trickle to finish off. I’m not sure what all this means but it’s interesting.
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Let me see if I can find a discharge curve, it will help you see my point... :)
 
Here we go.
181048jn4sl2katkt4k4xn.jpg

So this isn't a perfect example, but it is typical of this cell type, so shows the point. You can see there is very little energy between 4.2v and 4.16v or so, certainly not close to 5% capacity, I'd be surprised if it was as high as 1%.

Unless... The CATL chemistry is significantly different and has a more linear discharge down from 4.2v, but I'd doubt it.
 
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Interesting how the rate over time changes with big drop off at the end. What causes that?
 
EVMid said:
My AS when fully charged reads 450 volts does this number suggest my MY needs the latest BMS upgrade? I got the car in November.
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Had a BMS upgrade today as was told the last software update caused a bit of a problem - I have complained about the reduced range since the last update and today MG have offered to pay for my first service as a gift towards more charging that I have incurred !!!
 
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