charging to 100%

[Scoozy]

That's right they do but they don't mention that it also balances below 100% . Mine is on a dumb EVSE so gets balanced virtually every time I charge , don't know wether that's good or not. Yes I do sometimes go to 100% .

Correct, i have a smart charger Smappee EV Wall and it balance every time i charge the battery. I see the end time of charging and after that I takes the time to balance the cells.

 

[Rolfe]

That's interesting. So it's not just the SR that balances every time, the LR will also do it when it gets the chance.

 

[Themist0]

How do you tell it’s balanced, am I missing a screen somewhere

 

[siteguru]

When charging, if the charge rate drops to about 200W (0.2kW) then it's doing a balance.

 

[Rolfe]

Mine drops to 20 watts, usually. I don't think I've ever seen it over 80 watts while it's balancing.

 

[Themist0]

I’m never awake in the middle of the night to check

 

[DBedford]

The advice from MG is:

• Normally charge to 80%
• 100% charge at least once a month and when you need it.

Regularly charging to 100% will have an effect, will be minimised if you immediately discharge the battery and use it, but will probably still affect overall degradation.

However, we are only talking a few percent over years so unless you are keeping the car for many years, it really won't make any difference.

Bear in mind that even Nissan Leafs, who don't have active thermal management and degrade much more quickly are fine for the first 5 years or so and even when older there are plenty of people running around with 2/3 or 1/2 the original range without problems.

With the MG4 degradation will be much less than this whatever you do with charging.

Range
So MG4 or ZS long range : approx. 273 mile 100% charge.
But then charging to 80% on the LR models the range is down to 218 mile. And that’s the range of the SR model !
So why isn’t the same battery technology found in the SR models also used in the LR models, so the longer range could be used daily?

 

[Ian Key]

Range
So MG4 or ZS long range : approx. 273 mile 100% charge.
But then charging to 80% on the LR models the range is down to 218 mile. And that’s the range of the SR model !
So why isn’t the same battery technology found in the SR models also used in the LR models, so the longer range could be used daily?

Because the SR battery isn't as fuel dense so takes up more room per kWh. In simple terms a 64kWh battery the same type as in the SR wouldn't fit because it would need to be bigger.

 

[val33]

Range
So MG4 or ZS long range : approx. 273 mile 100% charge.
But then charging to 80% on the LR models the range is down to 218 mile. And that’s the range of the SR model !
So why isn’t the same battery technology found in the SR models also used in the LR models, so the longer range could be used daily?

I'm not sure if I am misunderstanding or you are. You can charge the LR to 100% every day, if you are driving it long distances every day, what you are advised not to do, is to charge to 100% and keep it there or only drive to the shops and back. In that situation its better for the battery to be only charged to 80%.

 

[Rolfe]

I’m never awake in the middle of the night to check

I don't have a variable tariff and charge on the granny charger any time I feel like it. Any time I look, after getting to 100% it drops to 20 watts (with occasional fluctuations) for half an hour before announcing that it's done. Same thing when I used the type 2 chargers next to my friend's home when I was staying there.

 

[tsedge]

Range
So MG4 or ZS long range : approx. 273 mile 100% charge.
But then charging to 80% on the LR models the range is down to 218 mile. And that’s the range of the SR model !
So why isn’t the same battery technology found in the SR models also used in the LR models, so the longer range could be used daily?

LFP technology (as used on the SR) is cheaper but it is also less space efficient (so it would not fit in the MG4 with a larger capacity pack), it is heavier per-kWh and it is slower to charge/discharge. It does last longer, roughly twice the charge/discharge cycles before significant battery degradation.

Higher performance EVs use NMC across the industry (eg Tesla), because of its better performance characteristics. This is normal.

As others have pointed out elsewhere, you can use the whole range of a LR daily, but doing so will have some longevity consequences.

However, battery longevity is typically longer than the car lifespan anyway (most batteries of all types will be reused for stationary storage), so this doesn't really matter unless you want to keep your MG4 for 10+ years.

Battery lifespan is really a non issue with the latest EVs, it is already much better than ICE engines, which are so pushed to the limit for emissions control and economy that they increasingly now need major work from as little as 50,000 miles. But even if your ICE engine will do 200,000 miles, your SR MG4 battery should do 400,000+

 

[Rolfe]

As I understood it, the problem with the NMC batteries and charging to 100% isn't how many times you take the battery to 100%, but how long you leave it sitting at 100%. Something about the space taken up by all the lithium ions crowding into the cathode? Or anode?

Correct me if I'm wrong, but I thought it was OK to charge the LR batteries to 100% every day, so long as you set off and use that charge ASAP so that it doesn't sit for a long time at that SoC. Or does even a couple of hours every morning add up?

 

[tsedge]

As I understood it, the problem with the NMC batteries and charging to 100% isn't how many times you take the battery to 100%, but how long you leave it sitting at 100%. Something about the space taken up by all the lithium ions crowding into the cathode? Or anode?

Correct me if I'm wrong, but I thought it was OK to charge the LR batteries to 100% every day, so long as you set off and use that charge ASAP so that it doesn't sit for a long time at that SoC. Or does even a couple of hours every morning add up?

Both charging to 100% and leaving the battery at 100% have negative effects in the long run (with NMC). Leaving at 100% is the bigger effect, but even if you always use it soon after there will be a negative effect from charging to 100%. This is because the battery degradation rises with higher battery voltages, so time at high states of charge speeds up battery breakdown.

However, these days neither of these battery effects really matters unless you are keeping the car for a long long time.

It is a bit like repeatedly revving an ICE car to the redline every day. You can do it, no problem, but over time it will increase engine wear. But who cares if you are only keeping the car for a year or two? If you want to keep it 10 years though, you won't drive it like that.

 

[Rolfe]

Thanks, that clarifies it. It's academic for me as I have the LFP battery, but it's good to be educated.

 

[memo]

All batteries LPF or NCM will last longer if charged only between 20 to 80% in fact between 50 to 60% for longest life but the difference between 20/80 and 50/60 is very little in longevity thats why you hear 20/80 so much. longevity goes down more when below 20 or above 80 and as tsedge said they like it even less if left at 100% for any lenght of time. but the effect is less on LPF than NCM and with modern batteries its not something i am worried about as they will outlast the car.

the real reason they say to charge a lpf battery to 100% isn't because it loves it, it is because the voltage (also each cells voltage is much lower than a ncm at max charge as well) in the discharge curve of a LPF battery is consistant thoughtout the discharge until the end when it drops of the cliff so the voltage sensor for the GOM doesn't really know what state of charge the battery has during the discharge as the voltage is the same. it only knows for sure when the battery is at 100% and can GUESS the state of charge going down by how you use it and kilometers. whereas a NMC battery the voltage gradually get lower as you discharge it, so the sensor and the GOM knows quite accurately the state of charge of your battery because of its voltage.

hence always charge a LPF battery to 100% so it can reset the gom. You still need to charge a nmc battery to 100% occasionally as well but it is less important for knowing its state of charge

 

[Rolfe]

I think someone said that already, but you have explained it extremely well, thank you.

 

[DBedford]

I'm not sure if I am misunderstanding or you are. You can charge the LR to 100% every day, if you are driving it long distances every day, what you are advised not to do, is to charge to 100% and keep it there or only drive to the shops and back. In that situation its better for the battery to be only charged to 80%.

Totally with you, just saying the LR is carrying extra battery around for those once in a while trips, when a SR may be more convenient .

 

[siteguru]

Given the higher Wh per kg of the NMC battery, the 64kWh battery pack is not much difference in weight vs the 51kWh LFP pack.

 

[Rolfe]

How much does £2,500 weigh, though?

 

[siteguru]

I agree ... £2.5k pays for a lot of charging sessions, even at 79p per kWh. I was just assuaging the assumption that the bigger capacity battery would be significantly heavier.