MG4 LFP/NMC batteries

[Haggis]

Indeed : I do 1000 miles a month, so in 13 months, I've worked out that I've done 75 full cycles (13000 miles / 175 average range - 150 winter, 200 summer) (Standard LFP battery). At 6 months (6500miles), I had 2.8% degredation, and 6-7 months later (13000miles), I've now got a 3.6% degredation so it is curving in the right direction - for LFP they say around 10-20% degredation at 10 years - but who really knows?

My i-miev is 11 years old and it is perhaps just a bit better. But it has a lithium ion battery. It has only ever been charged using a household socket. And it only has 70,000 Kms on it. But now it's off the road. And it's because one cell...only one cell has dropped. I'm going to put it up on the hoist take the battery out and replace that cell and perhaps the cells around it. Check all cells and re-balance the cells. But there is no doubt the life of the vehicle is coming to an end unless I change the complete battery. And that is uneconomic. So I will try and fix it whilst I look to buy another EV. Either a new MG4 or a 12 month old TESLA with about 20,000 Kms on it seems the choice at the moment.

 

[MoDolph]

And there is a difference between the models with a LFP and NMC battery isn't there?

Yes and people are trying to explain them to you but you only seem to want to believe that LFP is always better and more suitable than NMC. Your focussing on the supposed better cycle life of LFP without considering the magnitude of the numbers involved.

To try to illustrate this I have made a basic model in Excel where I can enter the cycle life of each car and compare what the real world range will be after a given number of miles driven:

The above is assuming a life to 70% SOH of 3,000 cycles for NMC and 6,000 for LFP. Even being twice as bad, the NMC still has more real world range after 400k miles.

Even if the NMC only lasted 1,000 cycles and the LFP lasted 100,000 it would still take 170k miles to break even, well beyond when most vehicles are scrapped:

For all of those miles you are also getting faster charging and slightly better low temperature performance.

These cycle lives are based on charging both to 100%, if you only charge the NMC to 80% you can extend the number of miles until the break even point. This is why it's only a recommendation and if you need/want to always charge to 100% it it is not a problem.

The reason I chose 3,000 cycles for NMC is because the best data I have found is from CATL themselves. The following is taken from a presentation in 2017 where they are discussing ways to make higher density batteries. Although the basic chemistry is the same (NMC 532), they are charging it to 4.4 V instead of 4.2 V. Even being cycled at what would be, in our cars, 113%-0% they still managed 1800 cycles to 80% SOH. To 70% SOH which is what is more typically quoted for end of life you get ~2700 cycles.

 

[jpk]

I just signed up to the 14 day free trial for abrp premium and got this live data about the battery

 

[Rolfe]

Yes and people are trying to explain them to you but you only seem to want to believe that LFP is always better and more suitable than NMC. Your focussing on the supposed better cycle life of LFP without considering the magnitude of the numbers involved.

To try to illustrate this I have made a basic model in Excel where I can enter the cycle life of each car and compare what the real world range will be after a given number of miles driven:

View attachment 20918
The above is assuming a life to 70% SOH of 3,000 cycles for NMC and 6,000 for LFP. Even being twice as bad, the NMC still has more real world range after 400k miles.

Even if the NMC only lasted 1,000 cycles and the LFP lasted 100,000 it would still take 170k miles to break even, well beyond when most vehicles are scrapped:

View attachment 20920
For all of those miles you are also getting faster charging and slightly better low temperature performance.

These cycle lives are based on charging both to 100%, if you only charge the NMC to 80% you can extend the number of miles until the break even point. This is why it's only a recommendation and if you need/want to always charge to 100% it it is not a problem.

The reason I chose 3,000 cycles for NMC is because the best data I have found is from CATL themselves. The following is taken from a presentation in 2017 where they are discussing ways to make higher density batteries. Although the basic chemistry is the same (NMC 532), they are charging it to 4.4 V instead of 4.2 V. Even being cycled at what would be, in our cars, 113%-0% they still managed 1800 cycles to 80% SOH. To 70% SOH which is what is more typically quoted for end of life you get ~2700 cycles.

View attachment 20922

Brilliant post, @MoDolph.