MG Owners > 1 year .. Battery Health

[Cricketer007]

reaching out to owners who have had their MG ZS EV for a good year and put some decent mileage on their cars ....

are you still experiencing good battery health i.e after a AC slow charge, are you still getting 450V and 163 miles range on normal?

or are signs of battery wear setting in?

thanks

 

[Mark Holmes]

Over 1 year and nearly 17000 miles with no problems that I am aware off regarding my battery or range.

 

[Paulie68]

I'm on 12k, battery seems the same as ever, range just as good as new.

Oddly, I have noticed the last couple of charges, my voltage is showing as 448v rather than 449v, but balancing wasn't complete before I used the car again. I'll be keeping an eye on it.

 

[Cocijo]

Do we know what the definitive test is for checking battery degradation?

 

[rpannell]

I'm on 14,000 miles with a reported 98.7% SOH, however the SOH stayed at 100% for ages then has recently started dropping quickly from 100%. I cannot detect any change in range, or amount to charge the car, but then I probably would not notice 1.3%.
I wonder how MG measure the SOH? Is it based on the number of charges, the mileage, the internal resistance, the max battery voltage etc. Without knowing how MG measure it, it is impossible to know whether to believe the result.
I'm using the Thai app to display the SOH.

 

[JodyS21]

I'm on 14,000 miles with a reported 98.7% SOH, however the SOH stayed at 100% for ages then has recently started dropping quickly from 100%. I cannot detect any change in range, or amount to charge the car, but then I probably would not notice 1.3%.
I wonder how MG measure the SOH? Is it based on the number of charges, the mileage, the internal resistance, the max battery voltage etc. Without knowing how MG measure it, it is impossible to know whether to believe the result.
I'm using the Thai app to display the SOH.

I think it has to be based on max cell voltage, it is the only thing I think it has to work from.

Have you had your BMS updated yet or are you still on the **R17 version?
Your SOH has gone down since I got your data - have you done many miles/recharges since then?

It'd be interesting to see your fully charged data over time.

 

[AbuG]

Do we know what the definitive test is for checking battery degradation?

Would have to run down battery to empty and then recharge to 100% and see how much energy it accepted... Then repeat yearly under the same climate conditions. Percentage difference would be degradation.

 

[rpannell]

I think it has to be based on max cell voltage, it is the only thing I think it has to work from.

Have you had your BMS updated yet or are you still on the **R17 version?
Your SOH has gone down since I got your data - have you done many miles/recharges since then?
View attachment 2711
It'd be interesting to see your fully charged data over time.

In my case, the SOH has reduced but I have not done any 100% charges during that reduction, so the car is not using the maximum voltage as its measure of SOH. Actually we know that as the cars with the bad BMS were still reporting 100% SOH. The car could be using distance covered, the number of charges or perhaps some form of change of voltage versus coulombs added (or removed) at some defined SOC to estimate the SOH.
I tend to charge little and often - I add 35% SOC (7 hrs on a granny) every time the battery is below 50% SOC, plus the odd topup at Tesco, so it may be that the car is using the number of charges to estimate the SOH.

 

[JodyS21]

In my case, the SOH has reduced but I have not done any 100% charges during that reduction, so the car is not using the maximum voltage as its measure of SOH. Actually we know that as the cars with the bad BMS were still reporting 100% SOH. The car could be using distance covered, the number of charges or perhaps some form of change of voltage versus coulombs added (or removed) at some defined SOC to estimate the SOH.
I tend to charge little and often - I add 35% SOC (7 hrs on a granny) every time the battery is below 50% SOC, plus the odd topup at Tesco, so it may be that the car is using the number of charges to estimate the SOH.

Very very interesting....

I believe the bad bms cars will still be finding out what the max voltage cell is and therefore SOH correctly, as they'll charge until the first cell hits its max voltage, they are just low on total voltage as other cells are lower/out of balance. So if they hit the wanted max cell voltage it'd think it's 100% SOH still (I believe).

I just don't know about this. I'd be very surprised that it's not pretty much just worked out on voltage; from reading up on it, it is very complex to do it any other way.

Really, you're doing everything perfectly from a battery life perspective, not charging it to 100% all the time/letting it go really low, so your car battery should do better than others on similar mileage.
One thing we can be sure of, MG will obviously have set it up to not reduce the figure if they can help it to avoid getting to the warranty claim point!

How many miles have you done?
[edit] I've just noticed you've done 14,000 miles, that's less than Mark Holmes 17,000 and he's on 100% SOH.
That doesn't make sense based on your battery charge care regime?!?!?

 

[Paul225]

reaching out to owners who have had their MG ZS EV for a good year and put some decent mileage on their cars ....

are you still experiencing good battery health i.e after a AC slow charge, are you still getting 450V and 163 miles range on normal?

or are signs of battery wear setting in?

thanks

This is today’s reading after a podpoint overnight charge - car is 14 months old !!

 

[JodyS21]

This is today’s reading after a podpoint overnight charge - car is 14 months old !!

As per my reply to your same post on another thread.
You have the dodgy BMS if that is your full charge voltage.
You haven't reset your accumulated trip to give a default comparable range.

 

[Paul225]

As per my reply to your same post on another thread.
You have the dodgy BMS if that is your full charge voltage.
You haven't reset your accumulated trip to give a default comparable range.

Do you need to reset accumulated trip after every charge then ?? I did reset it earlier this week ?? Thanx

 

[John G]

reaching out to owners who have had their MG ZS EV for a good year and put some decent mileage on their cars ....

are you still experiencing good battery health i.e after a AC slow charge, are you still getting 450V and 163 miles range on normal?

or are signs of battery wear setting in?

thanks

After one year and 10500 miles I had 100% state of health with 455v before service and update and now 449 after, but no problem with range throughout year. Only the usual cold and wet reduction but even this is less on a longer trip. Energy cost 1p per mile.

 

[rpannell]

Very very interesting....

I believe the bad bms cars will still be finding out what the max voltage cell is and therefore SOH correctly, as they'll charge until the first cell hits its max voltage, they are just low on total voltage as other cells are lower/out of balance. So if they hit the wanted max cell voltage it'd think it's 100% SOH still (I believe).

I just don't know about this. I'd be very surprised that it's not pretty much just worked out on voltage; from reading up on it, it is very complex to do it any other way.

Really, you're doing everything perfectly from a battery life perspective, not charging it to 100% all the time/letting it go really low, so your car battery should do better than others on similar mileage.
One thing we can be sure of, MG will obviously have set it up to not reduce the figure if they can help it to avoid getting to the warranty claim point!

How many miles have you done?
[edit] I've just noticed you've done 14,000 miles, that's less than Mark Holmes 17,000 and he's on 100% SOH.
That doesn't make sense based on your battery charge care regime?!?!?

It's a bit of a mystery how the car estimates the SOH. From the observations on my car (where the SOH has decreased during a time when no 100% charges were done) it cannot be by reference to the max cell voltage. It's important to know otherwise an owner could change their charging profile to minimise the displayed SOH reduction but in doing so increase the true degradation. For example, if the car estimates the SOH on the number of charges (not complete charge cycles) charging the car from say 5% - 100% would minimise the number of charges but is likely to increase the true degradation.
I'm still on R17 BMS so I think I will update this to see if this helps the fast degradation.

 

[Cocijo]

Someone asked me the other day ‘why doesn’t your car just have one big battery?’ Which is an interesting question that makes you think of why battery packs are built from many individual cells - the benefits and the downsides.

It is inevitable that as the batteries age some cells will outperform others. At this point the bms tries to protect these degraded cells from further damage (as it has done since they were new).
If it were possible for example to isolate these degraded cells, then the remaining pack would show good health. It’s usually a few degraded cells that can affect how the pack as a unit performs.

This is one of the reasons why manufacturers first look to replace cells to bring a pack back to an acceptable level of health before considering replacing the whole pack.
I wonder if a customer could in the future buy just a pack of cells and replace the under-performing ones rather than the complete pack? I guess adding new cells might also put pressure on the other ageing cells in the pack so the only real longer term solution is a new pack? But it would certainly be cheaper for cars that are out of warranty.

I use quite a few lion batteries at home for security cameras etc and the same batteries with the same use have variations in performance and longevity so I guess this is normal.
My iPhone tells me that my battery health is 98% but i’ve no idea how it calculates this - I would guess it has to be voltage, but as with our cars showing a voltage and also being able to perform under high rates of discharge and load are different areas.

 

[Paul225]

Today’s details on battery after charging fri night and travelling 2 miles yesterday - this is after switch on !

 

[JodyS21]

Today’s details on battery after charging fri night and travelling 2 miles yesterday - this is after switch on !

Sorry, Not sure what you are trying to show?

No point in using anything for comparison other than getting the figures after doing a full AC charge and balance - don't do any miles etc, unplug it and get the reading straight away - start without brake pedal pressed to ensure the HV battery is under no load.
Make sure the accumulated trip says zero so that the range calculation is using the default settings, if it has any data on the trips then the range calculation shown will be based on your diving data stored and not the default driving data.

 

[JodyS21]

It's a bit of a mystery how the car estimates the SOH. From the observations on my car (where the SOH has decreased during a time when no 100% charges were done) it cannot be by reference to the max cell voltage. It's important to know otherwise an owner could change their charging profile to minimise the displayed SOH reduction but in doing so increase the true degradation. For example, if the car estimates the SOH on the number of charges (not complete charge cycles) charging the car from say 5% - 100% would minimise the number of charges but is likely to increase the true degradation.
I'm still on R17 BMS so I think I will update this to see if this helps the fast degradation.

I agree, it would be beneficial to be told so that you have the option of altering your charging profile appropriately if you wish to.

I guess if the car doesn't get any 100% charges it still kinda needs to know roughly what the SOH is to do the battery management.
Maybe it does use the number or charges or it maintains an accumulative tally of the charge percentage that has been put into the car.
The only thing is that makes no sense to getting a true SOH and, people with similar mileage would then have similar SOH.

I wonder if your SOH would go back up if you did a few 100% charges/balances.
Remember until you do a 100% charge it won't be doing any balancing.

 

[Kithmo]

Someone asked me the other day ‘why doesn’t your car just have one big battery?’ Which is an interesting question that makes you think of why battery packs are built from many individual cells - the benefits and the downsides.

It is inevitable that as the batteries age some cells will outperform others. At this point the bms tries to protect these degraded cells from further damage (as it has done since they were new).
If it were possible for example to isolate these degraded cells, then the remaining pack would show good health. It’s usually a few degraded cells that can affect how the pack as a unit performs.

This is one of the reasons why manufacturers first look to replace cells to bring a pack back to an acceptable level of health before considering replacing the whole pack.
I wonder if a customer could in the future buy just a pack of cells and replace the under-performing ones rather than the complete pack? I guess adding new cells might also put pressure on the other ageing cells in the pack so the only real longer term solution is a new pack? But it would certainly be cheaper for cars that are out of warranty.

I use quite a few lion batteries at home for security cameras etc and the same batteries with the same use have variations in performance and longevity so I guess this is normal.
My iPhone tells me that my battery health is 98% but i’ve no idea how it calculates this - I would guess it has to be voltage, but as with our cars showing a voltage and also being able to perform under high rates of discharge and load are different areas.

I suspect safety is the reason we don't have one big battery, accidentally touching 450v DC is instant death. When the battery is disconnected there is a safety fuse that lowers the touchable connectors to a safer, more survivable (but still shocking), voltage.
I swapped out two cells from SWBO's old 2006 Prius earlier this year but couldn't get new ones, Toyota will supply you with the whole pack but not individual cells at a cost of £1100. The two second hand ones I bought were £19 each, so I repaired the car for £38.
I think it'll be the same for the MG, you either buy a whole pack new or you go to a breakers.

 

[JodyS21]

Someone asked me the other day ‘why doesn’t your car just have one big battery?’ Which is an interesting question that makes you think of why battery packs are built from many individual cells - the benefits and the downsides.

It is inevitable that as the batteries age some cells will outperform others. At this point the bms tries to protect these degraded cells from further damage (as it has done since they were new).
If it were possible for example to isolate these degraded cells, then the remaining pack would show good health. It’s usually a few degraded cells that can affect how the pack as a unit performs.

This is one of the reasons why manufacturers first look to replace cells to bring a pack back to an acceptable level of health before considering replacing the whole pack.
I wonder if a customer could in the future buy just a pack of cells and replace the under-performing ones rather than the complete pack? I guess adding new cells might also put pressure on the other ageing cells in the pack so the only real longer term solution is a new pack? But it would certainly be cheaper for cars that are out of warranty.

I use quite a few lion batteries at home for security cameras etc and the same batteries with the same use have variations in performance and longevity so I guess this is normal.
My iPhone tells me that my battery health is 98% but i’ve no idea how it calculates this - I would guess it has to be voltage, but as with our cars showing a voltage and also being able to perform under high rates of discharge and load are different areas.

I get the impression that no cars use a single battery.
There's always going to be multiple cells, you can't have just a single cell/battery.
It makes total sense to be modular, the battery packs can then be used in different configurations - capacities/size/layout etc, they can be replaced separately etc.