Battery Charging / Range Anomalies - anyone have the same experience?

[MTS]

Hi all, just want to share a few strange things happening recently and if anyone has had similar experience - MG ZS Mk2 SR, current odometer reading 1800miles:

1) Recently I've been seeing around 110 miles travelled with still 45% left in battery. Really chuffed and thinking that gives me around 200miles real world range which is consistent with the 4miles/kwh reading. Then the battery drops really rapidly and I've lost 20% doing the next 20 miles! All other things unchanged with the previous 110 miles in terms of driving style, route etc. I guess if I was to keep driving till the battery dies, I'm only seeing around 140-150miles. Now some people may say as we get into colder weather getting around 150miles in an SR is probably about right, but it's just the way the battery depletes at such an inconsistent manner which is worrying.

2) It's happened once where the battery suddenly stayed at 64% for over 20 miles which I knew was not right when I should have lost around 10% of battery. I popped into the local tescos and charged it for 10 minutes thinking a software bug was causing it and a quick charge might 'reset things', it seemed to have worked. It was all back to normal until it dropped to around 40%. Then the next day, saw that it had dropped to 30% and I lost 10% overnight. It seems that suddenly the computer monitoring the battery may have 'woken up' and realised I did 20 miles with the battery % stuck and decided to drop by 10% to correct itself!!

3) Recently when charging at a 7kw charger, it's charges very consistently from say 30% to 85% over a few hours. Then suddenly when I 'm checking on the app, it jumps from 85% to 95% in a matter of minutes, then after another few minutes it says 100% charge and has stopped. Now there's no way that the battery could have gone from 85% to full in 10 minutes. This is happening quite consistently now.

I've not taken the car back to MG yet - not sure if it's something anyone else has experience with this, is it my battery or a software issue?

 

[N2STY]

I think this it to be accepted with SR batterys as there is not much voltage Curve from high to low this is why it's the bms that likes to see 100% more than the battery it gives the gom a fighting chance

 

[Luke]

Hi MTS, thanks for posting this! I have the same car, and have experienced exactly the same things.

1) I've worked out that most of the time I get close to 4 miles per kWh, which is approximately 2 miles every battery percentage. On the motorway this is less, and closer to 1.6 miles per percent of battery (it's just easier to work it out this way in my head while driving). Randomly the car will get 1 mile per percent despite showing 4 miles per kWh in the display. It happened recently on a long drive and I decided to top it up at a public charger to make sure I made it to my destination. I only charged it 20%, but after that, it then consumed the battery at the expected rate.

2) Yesterday I was doing the usual "Dad taxi" driving taking my kids to all their Saturday clubs. The battery was at 72%, and was 61% after driving 19 miles. However it then remained "stuck" at 61% for the next 20 miles which was disconcerting, and even would occasionally go back up to 62% if I braked. I ended up charging the car when I got home using my 7 kWh wall charger and it now seems to be behaving as normal expected again.

3) Our local Aldi has a free 7 kWh charge point, and I often use it to top up the battery while shopping. I normally get anywhere from 8-12% battery depending on how long I'm in for. On a recent charge I got 4.029 kWh on a 35 minute charge, which should have been around 8% battery, but it showed as 14% battery.

I'm hoping it's a software issue rather than an issue with the battery. All the software on the car feels very buggy, like it's a beta release. I've heard there are some firmware updates already with issues like the DAB radio intermittently cutting off. Perhaps a firmware update is needed for the battery too?

 

[MTS]

I think this it to be accepted with SR batterys as there is not much voltage Curve from high to low this is why it's the bms that likes to see 100% more than the battery it gives the gom a fighting chance

Hi, would you mind elaborating on this as I am not really technically minded enough to understand about the voltage curve and what it does? In layman terms, are you suggesting it is normal for the SR? Thanks!

 

[MTS]

Hi MTS, thanks for posting this! I have the same car, and have experienced exactly the same things.

1) I've worked out that most of the time I get close to 4 miles per kWh, which is approximately 2 miles every battery percentage. On the motorway this is less, and closer to 1.6 miles per percent of battery (it's just easier to work it out this way in my head while driving). Randomly the car will get 1 mile per percent despite showing 4 miles per kWh in the display. It happened recently on a long drive and I decided to top it up at a public charger to make sure I made it to my destination. I only charged it 20%, but after that, it then consumed the battery at the expected rate.

2) Yesterday I was doing the usual "Dad taxi" driving taking my kids to all their Saturday clubs. The battery was at 72%, and was 61% after driving 19 miles. However it then remained "stuck" at 61% for the next 20 miles which was disconcerting, and even would occasionally go back up to 62% if I braked. I ended up charging the car when I got home using my 7 kWh wall charger and it now seems to be behaving as normal expected again.

3) Our local Aldi has a free 7 kWh charge point, and I often use it to top up the battery while shopping. I normally get anywhere from 8-12% battery depending on how long I'm in for. On a recent charge I got 4.029 kWh on a 35 minute charge, which should have been around 8% battery, but it showed as 14% battery.

I'm hoping it's a software issue rather than an issue with the battery. All the software on the car feels very buggy, like it's a beta release. I've heard there are some firmware updates already with issues like the DAB radio intermittently cutting off. Perhaps a firmware update is needed for the battery too?

Hi Luke, interesting you are pretty much having the exact same issues as me. It's not serious enough to warrant a return to MG and might just have to wait until next service - I use the car daily and can't let them have it for a week or so to 'check'. Typically the dealer will probably say there's nothing wrong with it or can't find what's wrong and the battery is not exhibiting any problems to justify a warranty claim.
Indeed hope it's just a software glitch and an update next time it's in for service will solve it.....

 

[N2STY]

Hi, would you mind elaborating on this as I am not really technically minded enough to understand about the voltage curve and what it does? In layman terms, are you suggesting it is normal for the SR? Thanks!

Basically the standard range voltage is the same at 30% as it is at 70% so the car is just guessing state of charge so needs a 100% starting point to be more accurate

where the long range the voltage slowly drops which gives more accurate state of charge

 

[MTS]

Basically the standard range voltage is the same at 30% as it is at 70% so the car is just guessing state of charge so needs a 100% starting point to be more accurate View attachment 12093where the long range the voltage slowly drops which gives more accurate state of chargeView attachment 12094

Thanks, it's clear now but cannot understand why they've not been able to engineer it so that the battery reading is more linear or reliable.

It is frustrating how once below 40%, the range and battery drops at a rapid rate making it hard to plan longer journeys (I'm mainly using it for in town use so rarely do so).

I've not heard back from many other forum users which may mean they are probably are driving an LR or not having the same issues on the SR so I'm considering whether to take it back to the dealer for a check....will update here is I have any luck or have to live with this!

 

[N2STY]

Thanks, it's clear now but cannot understand why they've not been able to engineer it so that the battery reading is more linear or reliable.

It's just down to the chemistry of the battery unfortunately with its advantages come disadvantages

 

[MTS]

What's frustrating for me with this anomaly is that I can only reliably use the first 50-60% of the battery or about 110-120miles. After that, the battery drops at such a rapid rate that I don't have any idea when it'll be down to such a low level to be at risk not getting home.

Just to share, I've given my local MG dealer (RRG Stockport) a call to book in for a check on the battery and they have said that if they check the car and it is not a warranty issue or they find nothing wrong with the battery they will charge a 'fee' for checking over the car of around 120quid!

Now I'm not sure if they will really charge this, have booked a slot anyway and could always cancel!

Has anyone had a similar experience when booking a car in for something under warranty?

 

[N2STY]

@MTS this explains it well

 

[Coulomb]

It seems that the MG firmware is relying too much on voltage and not enough on the accumulated charge (Ah). It seems to me that they could do a lot better of a job than they are at present.

Maybe some day a firmware update will make it better, but MG aint Tesla when it comes to firmware and software quality, and especially responsiveness. Even critical things like chargers bricking cars doesn't seem to spur them into any sort of urgency. I guess it's one of the compromises with such a well priced car.

 

[N2STY]

But if tesla can't fix the problem how is mg?

 

[Lizzie]

I’ve a problem, we’re parked at Stansted with only 15 miles showing , how low can I go? Need to get to Tesco 6 miles away.

 

[N2STY]

You maybe OK but next time you may want to go to Tesco's before you park up to like 80% your really don't want it stored below 20%
Edit is there not a dc charger that's closer? I supposed worst case you can use the AA through MGs assist they can send a charge van if needed

 

[Luke]

Hi all, just want to share a few strange things happening recently and if anyone has had similar experience - MG ZS Mk2 SR, current odometer reading 1800miles:

1) Recently I've been seeing around 110 miles travelled with still 45% left in battery. Really chuffed and thinking that gives me around 200miles real world range which is consistent with the 4miles/kwh reading. Then the battery drops really rapidly and I've lost 20% doing the next 20 miles! All other things unchanged with the previous 110 miles in terms of driving style, route etc. I guess if I was to keep driving till the battery dies, I'm only seeing around 140-150miles. Now some people may say as we get into colder weather getting around 150miles in an SR is probably about right, but it's just the way the battery depletes at such an inconsistent manner which is worrying.

2) It's happened once where the battery suddenly stayed at 64% for over 20 miles which I knew was not right when I should have lost around 10% of battery. I popped into the local tescos and charged it for 10 minutes thinking a software bug was causing it and a quick charge might 'reset things', it seemed to have worked. It was all back to normal until it dropped to around 40%. Then the next day, saw that it had dropped to 30% and I lost 10% overnight. It seems that suddenly the computer monitoring the battery may have 'woken up' and realised I did 20 miles with the battery % stuck and decided to drop by 10% to correct itself!!

3) Recently when charging at a 7kw charger, it's charges very consistently from say 30% to 85% over a few hours. Then suddenly when I 'm checking on the app, it jumps from 85% to 95% in a matter of minutes, then after another few minutes it says 100% charge and has stopped. Now there's no way that the battery could have gone from 85% to full in 10 minutes. This is happening quite consistently now.

I've not taken the car back to MG yet - not sure if it's something anyone else has experience with this, is it my battery or a software issue?

A quick follow up on this, I saw a video about equalisation charging on the previous MG ZS model. This is where you charge your EV to 100% with your slow charger, but leave it connected. You will see that even though the battery is full, the status still says it's charging but a very small amount. It can take a few hours after fully charging to complete. I tried it and the battery seems to be performing much more reliably again. Apparently, this is worth doing at least once every few months.

 

[Coulomb]

Apparently, this is worth doing at least once every few months.

Or better yet, once per month.

 

[Lovemyev]

A quick follow up on this, I saw a video about equalisation charging on the previous MG ZS model. This is where you charge your EV to 100% with your slow charger, but leave it connected. You will see that even though the battery is full, the status still says it's charging but a very small amount. It can take a few hours after fully charging to complete. I tried it and the battery seems to be performing much more reliably again. Apparently, this is worth doing at least once every few months.

This really is great advice in principle, but we have to remember that there are some slight differences between Gen1 and Gen 2 models to certain extent, that maybe worth giving some thought.
The battery technology in the Gen 2 standard range and the Gen 2 longer range are different and therefore has a slightly different charging protocol.
In the standard range model, it is suggested that you charge to SOC of 100% all of the time.
This is backed up in the head settings of the charging screen of the car, because you are unable to lower the charging SOC to anything lower than 100%.
Therefore if you just plug in the car and let it do it’s own thing, then it is going to enter the battery balancing cycle, without you even noticing !.
The long range model of the Gen 2 is very different, as it is recommended to charge to a 80% SOC for regular journeys and then extend the charging cycle upto 100% SOC when you have the longer journeys to make.
It’s stands to reason then, is owners of the LR model are mostly carrying out shorter trips, then more often that not, they will not charging to 100% and then going on to carry out a balance cycle as often as a standard range owner will do.
The previous Gen1 model was similar to the standard range Gen2 with this respect then.
No delayed timer functions on the Gen1 did not help this situation either.
This whole charging / battery health thing, can be a total mine field to be totally honest.
If you are really interested in this subject and have a long time to read all of the opinions and comments on this subject, then search for the BMS thread on the forum.
But be aware, it is packed with brilliant facts, figures and informative content, but it can be heavy going on times.
Maybe not a bed time read .

 

[Luke]

This really is great advice in principle, but we have to remember that there are some slight differences between Gen1 and Gen 2 models to certain extent, that maybe worth giving some thought.
The battery technology in the Gen 2 standard range and the Gen 2 longer range are different and therefore has a slightly different charging protocol.
In the standard range model, it is suggested that you charge to SOC of 100% all of the time.
This is backed up in the head settings of the charging screen of the car, because you are unable to lower the charging SOC to anything lower than 100%.
Therefore if you just plug in the car and let it do it’s own thing, then it is going to enter the battery balancing cycle, without you even noticing !.
The long range model of the Gen 2 is very different, as it is recommended to charge to a 80% SOC for regular journeys and then extend the charging cycle upto 100% SOC when you have the longer journeys to make.
It’s stands to reason then, is owners of the LR model are mostly carrying out shorter trips, then more often that not, they will not charging to 100% and then going on to carry out a balance cycle as often as a standard range owner will do.
The previous Gen1 model was similar to the standard range Gen2 with this respect then.
No delayed timer functions on the Gen1 did not help this situation either.
This whole charging / battery health thing, can be a total mine field to be totally honest.
If you are really interested in this subject and have a long time to read all of the opinions and comments on this subject, then search for the BMS thread on the forum.
But be aware, it is packed with brilliant facts, figures and informative content, but it can be heavy going on times.
Maybe not a bed time read .

Very interesting, thanks for sharing!