Soh after 20k miles

[Tim Green]

Although the U-tubes were interesting, they were very basic and general, and said little about how SOH is actually measured (if at all).
The easiest approximation would be to have the software count the number of times the car was rapidly charged and to what extent, and apply a depreciation amount accordingly, and similarly to a lesser extent with normal (at home) charges.
On the other hand, the car is there to be used, so if one sticks to general good practice, the battery should last a good many years, similar to an ICE car.

 

[Bodgerx]

Although the U-tubes were interesting, they were very basic and general, and said little about how SOH is actually measured (if at all).
The easiest approximation would be to have the software count the number of times the car was rapidly charged and to what extent, and apply a depreciation amount accordingly, and similarly to a lesser extent with normal (at home) charges.
On the other hand, the car is there to be used, so if one sticks to general good practice, the battery should last a good many years, similar to an ICE car.

Cycles are specifically mentioned - which is what you are talking about with number of times charged.

 

[fred12345]

I finally managed to connect my cheapy ODB reader and Car Scanner app and it shows 92.32% SoH for our 2 year old standard range Trophy with 43,000 miles... for an ex-lease car, I guess it's not too bad ...

 

[Bodgerx]

I finally managed to connect my cheapy ODB reader and Car Scanner app and it shows 92.32% SoH for our 2 year old standard range Trophy with 43,000 miles... for an ex-lease car, I guess it's not too bad ...

Do you rapid charge much?

 

[fred12345]

Do you rapid charge much?

I just got it 10 days ago and only charged it twice on a slow home plug 2kW charge, not sure what the guy who was driving it before used to do, it's ex lease car...

 

[andymgzs]

For anybody who worries about battery degradation I don't think there is any need. Mostly home charged with the occasional rapid when needed.
View attachment 25699

Where did data come from. I ask because elsewhere on this site it references that MG have hard coded the SOH into the diagnostics.

Mine when battery is completely flat to fully charged takes 32kwh. Not 44.5kwh capacity.

73%!

Computer says 92%!

 

[tomhanman]

It’s 4 years old and gets balanced every 4-6 weeks. Local dealer reckons it’s as expected after 4 years, but it seems to have dropped fairly quickly since October when it was 92%.

Doing a deep discharge (as deep as possible, don't stop at 10%) followed by a full charge is not about balancing. As an aside balancing really shouldn't be of any significance with these virtually new cells. The deep discharge and charge cycles allow the coloumb counter to establish the actual amount of energy capacity remaining in the range used as opposed to continually trying to calculate it from theoretical look-up tables relating to voltage under partial load, curent in, temperature, current out etc.

You could also monitor the cell values when getting low, and getting full to see if there are any outliers. The tiny balance ability of these bms is just for maintenance, if there is a problem, the cell will most probably show itself at very low charge levels or very high.

Otherwise it is just degradation... I nearly made my wife choose the lfp version instead of the long range for the chemistry and it's supposed talents. But when I read the (fascinating, not) warranty and saw that they are the same for the two battery types, I figured that if they weren't confident enough in their lfp solution to extend the warranty, then neither was I.

Regards,
Tom.

 

[Bodgerx]

Doing a deep discharge (as deep as possible, don't stop at 10%) followed by a full charge is not about balancing. As an aside balancing really shouldn't be of any significance with these virtually new cells. The deep discharge and charge cycles allow the coloumb counter to establish the actual amount of energy capacity remaining in the range used as opposed to continually trying to calculate it from theoretical look-up tables relating to voltage under partial load, curent in, temperature, current out etc.

You could also monitor the cell values when getting low, and getting full to see if there are any outliers. The tiny balance ability of these bms is just for maintenance, if there is a problem, the cell will most probably show itself at very low charge levels or very high.

Otherwise it is just degradation... I nearly made my wife choose the lfp version instead of the long range for the chemistry and it's supposed talents. But when I read the (fascinating, not) warranty and saw that they are the same for the two battery types, I figured that if they weren't confident enough in their lfp solution to extend the warranty, then neither was I.

Regards,
Tom.

Yes, I doubt there are many buying the LFP version for it being LFP.

It's price and not needing the extra range.

 

[Lovemyev]

Traction battery degradation is going to happen regardless.
But if you intend to keep your car a while and it was purchased with your own hard earned cash, then of course you want to try and help slow down that trend in any way you possibly can.
However if it’s a lease car, then preserving the health of your pack, is the last thing on your mind TBH.
This attitude is very similar with ICE models in many respects.
Lease cars and especially X hire cars can receive a hard life in the very first few years of their existence.
Although the initial harsh treatment may not manifest itself straightaway, it can raise its head after the cars warranty has expired.
Which in the case of most manufacturers, is normally only 3 years in most cases.
Battery degradation is a bit like old age really I guess, you do your little bit, but you can’t prevent it from happening unfortunately .

 

[chris69]

Doing a deep discharge (as deep as possible, don't stop at 10%) followed by a full charge is not about balancing. As an aside balancing really shouldn't be of any significance with these virtually new cells. The deep discharge and charge cycles allow the coloumb counter to establish the actual amount of energy capacity remaining in the range used as opposed to continually trying to calculate it from theoretical look-up tables relating to voltage under partial load, curent in, temperature, current out etc.

You could also monitor the cell values when getting low, and getting full to see if there are any outliers. The tiny balance ability of these bms is just for maintenance, if there is a problem, the cell will most probably show itself at very low charge levels or very high.

Otherwise it is just degradation... I nearly made my wife choose the lfp version instead of the long range for the chemistry and it's supposed talents. But when I read the (fascinating, not) warranty and saw that they are the same for the two battery types, I figured that if they weren't confident enough in their lfp solution to extend the warranty, then neither was I.

Regards,
Tom.

Ok so this is confusing to me and counter intuitive to everything I have just read on several competent looking websites about lithium ion batteries. Surely a deep discharge damages a lithium ion battery, and partial discharges prolong life and capacity? Also doesn't the BMS in the car prevent a deep discharge by reserving a buffer? Or are you suggesting the BMS cannot measure SOH accurately unless at least one deep discharge is carried out?

 

[Peter WA]

Where did data come from. I ask because elsewhere on this site it references that MG have hard coded the SOH into the diagnostics.

Mine when battery is completely flat to fully charged takes 32kwh. Not 44.5kwh capacity.

73%!

Computer says 92%!

Based on the 44.5kWh I take it you've got a Mk1 vehicle?

When I had that one the SOH seemed in line with the range I was getting, and it changed in irregular intervals in slightly irregular steps. I took that to mean it actually was measured. Whether those measurements were correct, who knows.

When you extrapolate from what your charger tells you to capacity, one main thing to keep in mind is that the Mk1 has buffers at both top and bottom. You only ever get to use ~90% of the actual capacity. That means even a brand new battery would only have taken 40.x kWh from empty to full.

The other thing: where does the 32kWh figure come from? If it is a home charger I'd doubt the accuracy of that measurement. If it is a commercial (paid for) charger, the accuracy should be higher.

I finally managed to connect my cheapy ODB reader and Car Scanner app and it shows 92.32% SoH for our 2 year old standard range Trophy with 43,000 miles... for an ex-lease car, I guess it's not too bad ...

2 years old would be the Mk2 with 51kWh LFP battery? That's the one I have now and where I know for a fact that the SOH reported by the car is fake.

This is my SOH over time from a few days after I got the car (November 2022) until today. Straight line decline. A count down calibrated to ensure it stays above the 70% warranty cut-off for the whole warranty period.

The only anomaly was back in March last year. About a week after the only software update the car had the SOH increased a little bit. Likely a result of the software update, but hard to explain why it took a few days.

As to observed actual SOH: I believe that is very close to 100% still. I do not experience any reduction in range compared to new.

 

[Coulomb]

I doubt there are many buying the LFP version for it being LFP.

I would.

 

[tomhanman]

Ok so this is confusing to me and counter intuitive to everything I have just read on several competent looking websites about lithium ion batteries. Surely a deep discharge damages a lithium ion battery, and partial discharges prolong life and capacity? Also doesn't the BMS in the car prevent a deep discharge by reserving a buffer? Or are you suggesting the BMS cannot measure SOH accurately unless at least one deep discharge is carried out?

All correct Chris, but we're not talking about a lithium ion battery here. Fred has the lfp pack so lithium iron phosphate... they may very well involve some lithium ions but as far as the terminology goes we refer to nmc as lithium ion or ternary.

Anyhow, I did not suggest this as a daily medicine, just as a potential corrective measure. Not intended to improve the actual capacity of the battery cells, but to allow the bms to better understand the capacity of the cells.

But if this preprogrammed degradation being talked about is set in stone then that might lead to some interesting court time in a few years (assuming Trump isn't occupying them all).

I would like to believe that the preprogrammed figure is being used by the bms in the absence of proper measurable full cycles. But I may be optimistic.

Welcome to the world of trying to second guess your car. I've been doing it for a decade with Leafs... Still not sure how they're screwing me with the bms software 'upgrade' applied to my 30kWh. Just sure they are!

 

[Tim Green]

Well my Gen1 car is 4 years old and 21000 miles, and still returns 165 miles GOM every time, except in depth of winter. So either the battery is in reasonable condition or MG have some way of eliminating any degradation from the calculation.
Either way, it seems that battery condition is similar to "engine condition" in an ICE which was usually measured by oil consumption. Apart from general maintenance, the short answer is there is not much you can do about it.

 

[Bodgerx]

I would.

Would, but haven't?

 

[Coulomb]

Would, but haven't? [ Bought LFP because I consider it to be a desirable feature. ]

Yes. I bought my ZS EV before LFP was available from MG, and I'm not in a financial position to update for a while.

But if and when I do, an LFP battery will be highly favoured.

 

[Bodgerx]

Yes. I bought my ZS EV before LFP was available from MG, and I'm not in a financial position to update for a while.

But if and when I do, an LFP battery will be highly favoured.

Even though it's the lower capacity, lower range version?

 

[Coulomb]

All correct Chris, but we're not talking about a lithium ion battery here. Fred has the lfp pack so lithium iron phosphate... they may very well involve some lithium ions but as far as the terminology goes we refer to nmc as lithium ion or ternary.

I've noticed a tendency to regard the term "lithium ion" as referring only to the higher voltage chemistries such as NMC, NCA, LMO etc, and not the lower voltage chemistries like LFP and LTO (the latter standing for Lithium Titanate, a nominally 2.4V chemistry). But they all move lithium ions from anode to cathode or vice versa. So they all are genuinely lithium ion cells / batteries / chemistries.

I don't think that this one is so badly entrenched yet that we can give up on being scientifically correct.

 

[Coulomb]

Even though it's the lower capacity, lower range version?

Resuming that it meets our modest range needs, yes.

 

[Peter WA]

Resuming that it meets our modest range needs, yes.

Not only that, range of NMC is not what it is made out to be.

The Mk1 ZS EV makes available only a tad over 90% of the battery, the rest is buffers. And they failed to adjust the advertised range to reflect that. That meant instead of 263km it would have been a 240km vehicle when brand new. When I sold mine, degradation had started and reduced that further, to around 225km.

The Mk2 makes available about 96% of the battery, and the advertised range seems more conservative. I still get the 320km for most of my day to day driving.

Now assuming the Mk2 long range version is similar to the Mk1, seeing it has the same battery technology, how long until the actual range of the LR with NMC battery is identical to the standard range with LFP?

For the ZS EV the difference in battery size is sufficient that that might never happen, but the price difference is very substantial too.

For the MG4, the 64kWh version is quite pointless though for anyone who plans to keep the car for a long time.