Mg4 64kWh Battery Life

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umu1

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What is the degradation percentage of mg4 luxury? How often should i replace batteries? And are they replace all of them or a part of them?

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Are you talking about the traction battery guarantee under the 7 year warranty?
 
12 years, 1 million km is what CATL/MG think it'll do. That's likely to be to 70%.

Whether that is best/worst case or average is not known.

I have not yet seen a car that is reporting <100% SOH so we have no real world data yet.

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umu1 said:
Thank you so much
Click to expand...
No problem. What I find curious about that slide is that they choose to highlight the NMC battery's life instead of the LFP.

Everybody seems to think that LFP is better but all of the news articles and videos reference the same flawed paper so I'm not so sure.
 
MoDolph said:
No problem. What I find curious about that slide is that they choose to highlight the NMC battery's life instead of the LFP.

Everybody seems to think that LFP is better but all of the news articles and videos reference the same flawed paper so I'm not so sure.
Click to expand...
even if lpf is better , %70 heath and 1 million km is awesome
 
Well, disclaimer, I'm not an expert at all, but this is what I've managed to gather over the past six months.

NMC batteries are more energy-dense, and so have a longer range per kg/litre of battery weight/size. They also charge faster. This makes them more suitable for longer-range cars and cars that will be required to charge quickly (which tend to be the same thing). However this brings downsides. They aren't so long-lived (though that's relative, they're still pretty long-lived) and they're more finicky to look after. It's recommended not to leave them sitting around at either very high or very low states of charge for very long (under 20% or over 80%), so normally one would operate between these states unless preparing for and undertaking a long journey, when the battery won't be sitting around at any particular rate of charge. It is however recommended to charge them to 100% on an AC charger and let the cells balance by leaving the car plugged into the charger for as long as it takes, at least once a month. They also contain cobalt, which is known as a "conflict mineral" and is not beloved of environmentalists or human rights campaigners.

LFP batteries are less energy-dense, so have a shorter range for the same size/weight, and charge at only about 2/3rds the speed. However they are very long-lived and easier to look after. They don't mind being charged to 100% and left there, as the over-potential that causes electrolyte degradation in the NMC batteries is not present. You can just whack them up to 100% any time you want to. They like to be balanced at least once a week, but since you'll always be charging to 100% this happens without any extra effort. (They will balance every time they're taken to 100% on an AC charger.) They don't have any cobalt at all, so LFP owners can feel superior in this respect to anything else on the road.

If your normal daily mileage doesn't exceed the capacity of your battery and you can charge at home, the LFP is a bit of a no-brainer. You can practically charge it as you would your phone, not thinking about it too much. You can always leave home with enough charge to get you back, rinse and repeat. This applies so long as you're relaxed about your occasional long journeys needing an extra stop (because of the lower capacity) and the stops being a bit longer (because of the slower charging). This is why I went for the LFP.

On the other hand if you need to do journeys beyond the range of the car where time is pressing, go for the NMC. Also, if you can't charge at home and don't have easy access to an AC charger within walking distance, I think there's a lot to be said for the NMC. You can operate within the 20-80% range on rapid chargers (or grazing on AC chargers without going to 100%) most of the time, and you won't have to wait around too much. You only have to organise to leave the car to balance on an AC charger once a month. It will be easier to fuel more in the manner of an ICE car.

No doubt someone will be along to explain that this is wrong, or at best overly simplistic, but it's my current understanding.
 
I look at it this way, because the car is a consumer item it has to be idiot proof, so it has to have it's own protection mechanisms built in if the manufacturer is going to give a good warranty.
Here's where the BMS steps in. The BMS doesn't allow the consumer to actually charge the battery to 100%, it's actually at something like 97% when it says 100% in the car.
So what the MG 7 year HV battery warranty says to me is, if you charged your NMH (or NMC) battery to 100% every time and left it at 100% for days on end or if you let the battery run low and left it low for days on end, then you should still get 7 years of use where the battery won't degrade more than 70% SOH
In reality that says to me that if I look after my NMH/NMC battery by charging in the recommended "battery saver" region, with the occasional 100% balance, then I should get far more life out of it.
I reckon, looked after, the NMH/C battery will last for 10 plus years and have a good SOH, probably more than 70%, after that time and I can see LFP batteries even lasting 15 years or more.
So basically if you're planning on keeping the car for that length of time you need to nurse your NMH/C batteries, if you change your car often there's no need to worry about any of this.
 
There are two things that bother me about the NMC vs LFP debate:

There is no convincing evidence that I have found that suggests that automotive grade LFP have longer life than similar grade NMC.

LFP doesn't "like" to be charged to 100%. It still degrades more when at high SOC but the manufacturer's have somehow convinced everyone otherwise. They did this because LFP is more challenging when it comes to SOC estimation due to its flatter discharge voltage curve so it "has" to be charged to 100% regularly despite it being damaging.

These two videos are worth watching if your interested battery lifetime research. I will put a disclaimer that his area of research is NMC battery development (funded by Tesla) so he is likely to be a little biased but he is still one of the top researchers in the field.



 
In the videos I've watched, Euan McTurk is quite dismissive of any coddling of the LFP, possibly because he sees any degradation you might cause as being insignificant in terms of the overall life of the battery. He specifically states that the electrolyte degradation caused by the overpotential the NMC batteries can achieve doesn't happen on the LFP.

I think the point is that the LFP likes to be charged to 100% because it likes to balance, as discussed earlier, and that degradation is not in practice something to get seriously worried about. I'd like to hear him talk more about the LFP specifically though. Mostly, he just says something like "of course just in the NMC" when he's talking about things to avoid doing.

(I just saw the lengths of those videos. Ummm....)
 
Rolfe said:
I just saw the lengths of those videos. Ummm....
Click to expand...
They are long but worth it. The first one is the best and he only presents for maybe 40 mins with the rest being Q&A.

He is basically summarising research his team did to make NMC batteries last for 100 years being used daily for V2G applications.
 

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