MG5 SOH

Dt99idr

Dt99idr

Established Member
Joined
May 25, 2021
Messages
104
Reaction score
106
Points
43
Location
Yeovil, UK
Driving
MG5
Just had my 2nd service today after 26K miles. Allegedly my SOH is 100%... Half of me is thinking 'fantastic', the other half is thinking - have they actually checked...
Can anyone confirm a OBD2 dongle and android software i can use to check myself?

Thanks.
 
It's good up to a point. When new the car has a "top buffer" of around 6% which is their to improve the life of the battery (meaning charging to 100% is not that) and this buffer erodes over time. At some point the buffer will be eroded entirely and the remaining capacity will be seen to reduce.
So does that mean you have had no degradation? Some capacity will have been lost, clearly less than 6%, but you still have the same usable amount.
 
Dt99idr said:
Thank you @Alb Plugged I this afternoon and low and behold, 100% SOH. I think that's pretty good on a 2 year old car, certainly much better than I was expecting!
Click to expand...
If battery degradation is causing you concern, then can I suggest you take a look at this video below, it is pretty reassuring !.

 
I'm not concerned, but based on other reports on these forums I was expecting to have seen some % drop
 
BugEyed said:
It's good up to a point. When new the car has a "top buffer" of around 6% which is their to improve the life of the battery (meaning charging to 100% is not that) and this buffer erodes over time. At some point the buffer will be eroded entirely and the remaining capacity will be seen to reduce.
So does that mean you have had no degradation? Some capacity will have been lost, clearly less than 6%, but you still have the same usable amount.
Click to expand...
How do you know it's the buffer that erodes ?
2 possible scenarios,
1. the BMS enforces a 6% buffer so that regardless of any degradation it will still have 6% buffer to help with battery preservation, this will still show in reduced range in GOM.
or
2. As it degrades in your example by eroding the buffer what happens to the buffer when it reaches a state of health of 94%. Will it disappear so it no longer has a buffer and actually charges to true 100% from there on ?

I would rather hope the the former to protect the battery throughout it's life rather than the latter only protecting it for while.
 
I'd agree with you, but my understanding is that it is scenario 2. I suspect that manufacturers only care to massage the figures for the initial owners.
 
BugEyed said:
I'd agree with you, but my understanding is that it is scenario 2. I suspect that manufacturers only care to massage the figures for the initial owners.
Click to expand...
Using round numbers for ease, 61kWh battery gives a usable 57kWh battery, that is a 6% buffer to protect the battery when charging. So you think that the buffer itself decreases as the battery degrades to fill the void on reporting the SOH.
That is when the battery has degraded from 61 to say 59kWh (now 4% buffer), or from 61 to 57kWh (now 0% buffer) capacity it will still report 100% SOH.
If that were the case then the actual range would not drop for the first 6% actual degradation as it is a non-usable buffer that is eroding.

I still prefer the other scenario of a permanent 6% buffer whereby if capacity has degraded then the usable has also degraded.

It would be interesting to hear from anyone who has a less than 100% SOH what range is being reported with trips reset.

I have no particular knowledge as to how it reports SOH but struggle to imagine that the buffer to protect the battery just disappears, after all what is the BMS for ?
 
Gomev said:
I have no particular knowledge as to how it reports SOH but struggle to imagine that the buffer to protect the battery just disappears, after all what is the BMS for ?
Click to expand...

That's exactly what happens on Tesla and BMW to name but two.

MoDolph said:
If the top buffer is being eaten into then you would expect the fully charged voltage to gradually increase.
Click to expand...

Good point. And unusually that is something that we have access to (assuming it's accurate :rolleyes: ) and can monitor.
 
I would imagine that the initial degradation is easily hidden within the unused buffer. As the cells aren't taken close to their maximum voltage, there's no reason for the reduced capacity to become noticeable initially. When talking about a battery having a maximum usable capacity, you're really only talking about what the BMS is programmed to allow.

The hypothetical total capacity (were there no BMS) is potentially significantly higher, with the caveat that there would be irreversible damage from charging that much.

Batteries degrade over time, even with the best BMS and taking extreme care to avoid stressing them. If the degradation wasn't hidden in the buffer then the 100% SOH reported would be an obvious lie and we would notice reduced range.
 
Petriix said:
I would imagine that the initial degradation is easily hidden within the unused buffer. As the cells aren't taken close to their maximum voltage, there's no reason for the reduced capacity to become noticeable initially. When talking about a battery having a maximum usable capacity, you're really only talking about what the BMS is programmed to allow.

The hypothetical total capacity (were there no BMS) is potentially significantly higher, with the caveat that there would be irreversible damage from charging that much.

Batteries degrade over time, even with the best BMS and taking extreme care to avoid stressing them. If the degradation wasn't hidden in the buffer then the 100% SOH reported would be an obvious lie and we would notice reduced range.
Click to expand...
Indeed they do, The Leafs certainly with no cooling, but is it overhyped ? Are we worrying too much about it ?
Watching the video in post #5 above and also an Everything Electric podcast where they talked about China and the Mk1 MG5 mentioned as widely used as a taxi, with many having 350,000km on them and still going strong.
I say let the BMS do it's thing and just enjoy the driving. :)
 
Gomev said:
Indeed they do, The Leafs certainly with no cooling, but is it overhyped ? Are we worrying too much about it ?
Watching the video in post #5 above and also an Everything Electric podcast where they talked about China and the Mk1 MG5 mentioned as widely used as a taxi, with many having 350,000km on them and still going strong.
I say let the BMS do it's thing and just enjoy the driving. :)
Click to expand...
While I say take sensible steps to look after your battery (without inconveniencing yourself). MG don't have a perfect record with BMS software.
 
Petriix said:
While I say take sensible steps to look after your battery (without inconveniencing yourself). MG don't have a perfect record with BMS software.
Click to expand...
Quite right, sensible steps, just like life. I don't go out of my way to be careful it just happens normally day to day. I charge when I need, how I need and to how much I need and I don't worry about it.
Yes, I suffered the awful BMS cock-up on my ZS EV Mk1 but they fixed it and everything returned to hunky dory....eventually. :) and they seem to be doing a pretty reasonable job right now.
 
I'm in shock. Just had my Mk1 26th month old 7,500 mile ZS EV serviced and the battery SOH was 89% ***. I'm very worried, this is surely very bad. It had a BMS update at time same time. Previously it was charging to 450v for reference...
 
running flat said:
I'm in shock. Just had my Mk1 26th month old 7,500 mile ZS EV serviced and the battery SOH was 89% ***. I'm very worried, this is surely very bad. It had a BMS update at time same time. Previously it was charging to 450v for reference...
Click to expand...
That is why they have done the BMS update, sounds like your pack is out of balance.
Don't worry it should recover, did they explain that you will need to carry out a number of balance cycles now with a A/C charger to help re-balance the pack ?.
 
Lovemyev said:
That is why they have done the BMS update, sounds like your pack is out of balance.
Don't worry it should recover, did they explain that you will need to carry out a number of balance cycles now with a A/C charger to help re-balance the pack ?.
Click to expand...
It's an MG dealer, so no f help at all. I thought about doing several equalisation charges on a 7kw charger starting tomorrow. Thanks for your help and fingers crossed
 
running flat said:
It's an MG dealer, so no f help at all. I thought about doing several equalisation charges on a 7kw charger starting tomorrow. Thanks for your help and fingers crossed
Click to expand...
You may get more help from ZS onwers on the ZS forum bit of the site as the is for the MG5.
 
Support us by becoming a Premium Member

Latest MG EVs video

MG3 Hybrid+ & Cyberster Configurator News + hot topics from the MG EVs forums
Published
Subscribe to our YouTube channel
Back
Top Bottom