MG4 SE battery 1year SoH

[unbornidentity]

Just had my first service done at 12 months and 10500 miles. A battery health check was done and it said 88%. That was actually battery health not SoC as it was at 85% before I dropped it off and 80% when I collected it.

It was checked off as good and I’m not overly concerned about it but it seems pretty low. I’ve not done a <10% to 100% charge since about October and the battery was far from being warm but 88%?

I’ve looked after it and it’s only been rapid charged about 3 times in its life. My guess is that it’s the cold weather combined with no calibration charge but does anyone else have a SoH report from a service to compare?

The range of the car seems normal, performance seems normal. It can lose power at motorway speeds if you plant the throttle with <20% battery but it’s cold so makes sense and probably normal. But I’m a bit of a battery care nerd so 88% seems a bit odd.

 

[Everest]

I’m a bit of a battery care nerd so 88% seems a bit odd

I’ve not done a <10% to 100% charge since about October

One of those is wrong then

See page 296 (in the service and maintenance section) of user guide...

3 It is recommended using the vehicle at least once a month. Where possible it is recommended that you carry out a slow charging (equalisation charging) every month to extend the service life of high-voltage battery pack. The battery management system will monitor the status of the high voltage battery pack. After monitoring for a period of time, if an equalisation charge has not been carried out for some time the message centre in the instrument pack will display ‘Please Slow-charge the Vehicle’. At this time you must carry out an equalisation charge. For operation mode ,please refer to ‘Equalisation Charging’ in ‘Starting &Driving’ section.

 

[unbornidentity]

One of those is wrong then

See page 296 (in the service and maintenance section) of user guide...

3 It is recommended using the vehicle at least once a month. Where possible it is recommended that you carry out a slow charging (equalisation charging) every month to extend the service life of high-voltage battery pack. The battery management system will monitor the status of the high voltage battery pack. After monitoring for a period of time, if an equalisation charge has not been carried out for some time the message centre in the instrument pack will display ‘Please Slow-charge the Vehicle’. At this time you must carry out an equalisation charge. For operation mode ,please refer to ‘Equalisation Charging’ in ‘Starting &Driving’ section.

Nope! I let the car charge to 100% once a week on my home charger. I’m on about letting it get below 10% then charging to 100% LFP batteries have a near flat voltage curve and can only determine capacity by letting the voltage drop to near flat then fully charging. Read the manual thanks, even the bit you missed about what to do every 3 to 6 months.

 

[Everest]

Exactly. You'll need to let the BMS see a full discharge and charge back to 100% for it to re-calibrate the capacity. The BMS's coulomb counters will drift over time and won't give accurate values.

Have you checked with car scanner too?

Also this thread may be of interest..

MG4 51kWh LFP Battery Health

Hi everyone! I'm second owner. It had 10500 (6524 mile) kilometers on it when I bought it and SOH was 93.64% . Now my car is 17500(10873 mile) km and SOH is 93.15%. There is a difference -0.49% in 7000 kilometers. I just wanted to hear your ideas and suggestions. First of all is it normal...

www.mgevs.com

 

[unbornidentity]

Have you check with car scanner too?

Also this thread may be of interest..

MG4 51kWh LFP Battery Health

Hi everyone! I'm second owner. It had 10500 (6524 mile) kilometers on it when I bought it and SOH was 93.64% . Now my car is 17500(10873 mile) km and SOH is 93.15%. There is a difference -0.49% in 7000 kilometers. I just wanted to hear your ideas and suggestions. First of all is it normal...

www.mgevs.com

Nope was in for a service. I’m not worried about it yet. Just seems oddly low. If it is much less on the next service I’ll start looking at a warranty claim and if there is any hint of pushback at that point I’ll hand it back or trade in when the contract expires. Am planning to keep it though.

 

[mg4]

That is one serious degradation. For just over a year i got 0,9% degradation. Mine is a 77kWh battery though, so other chemistry. It is mostly used between 40% an 80%, I have newer seen a 'please slow charge' kind of a message and the car has done 2 trips each with 6000km of rapid charging it during them.

I think the car equalized the battery every time it is charging, since it always draws some small amount of power at the end of the charge, for 10-15 minutes.

Aside from the pattern above, I do about one or two trips per month where I charge it to 100% over night and leave it to do its equalization if needed. I do try to get below 10% before that. The rest of the weekend it is rapid charging.

I expected some high loss like 3% to 5% for the year, so once i got 0,9% I was pretty happy with it. I got this from the OBD2 dongle though.

So a loss of 12% capacity for me would be something to look into replacement under a warranty claim.

 

[gdog]

That is one serious degradation. For just over a year i got 0,9% degradation. Mine is a 77kWh battery though, so other chemistry. It is mostly used between 40% an 80%, I have newer seen a 'please slow charge' kind of a message and the car has done 2 trips each with 6000km of rapid charging it during them.

I think the car equalized the battery every time it is charging, since it always draws some small amount of power at the end of the charge, for 10-15 minutes.

Aside from the pattern above, I do about one or two trips per month where I charge it to 100% over night and leave it to do its equalization if needed. I do try to get below 10% before that. The rest of the weekend it is rapid charging.

I expected some high loss like 3% to 5% for the year, so once i got 0,9% I was pretty happy with it. I got this from the OBD2 dongle though.

So a loss of 12% capacity for me would be something to look into replacement under a warranty claim.

Not much of this info applies to a LFP battery. 88% is low for 1 year LFP. 95% sounds more normal.

 

[Tuareg]

I thought that MG warranty the battery for 7 years and a minimum of 70%, so no warranty claim at 88%. I would have thought you would have to hit the 70% value before making any such claim.

 

[T1 Terry]

I thought that MG warranty the battery for 7 years and a minimum of 70%, so no warranty claim at 88%. I would have thought you would have to hit the 70% value before making any such claim.

That sounds about right. I think because you haven't artificially reset the capacity back to 100% being 51kWh, it is getting close to telling you what the true capacity of the battery is ..... so I wouldn't worry too much. The next SoH will not be as savage I'm guessing, and bottoming out at around 82% or higher and maintaining that for yrs to come.

T1 Terry

 

[Ian Key]

Could be something as simple as the technician put the SOC in the wrong box and misread 85 as 88. Hopefully next time they'll put their glasses on

 

[gazza487]

I have a very early SE. Played about with my new Autel and its reported the SOH as 92% ish on 12k miles.

Not overly worried as there is no way this is a linear progression.

 

[unbornidentity]

That sounds about right. I think because you haven't artificially reset the capacity back to 100% being 51kWh, it is getting close to telling you what the true capacity of the battery is ..... so I wouldn't worry too much. The next SoH will not be as savage I'm guessing, and bottoming out at around 82% or higher and maintaining that for yrs to come.

T1 Terry

Yeah, I expect it’s just an oddity of the way it calculates it. Next time it’s due I do a <10% to 100% shortly before and see what happens. I know they lose more in the first year and settle down but 12% seems a lot!

If it does carry on at the same rate and it’s true though it will get claim level by the time it’s 3.

Could be something as simple as the technician put the SOC in the wrong box and misread 85 as 88. Hopefully next time they'll put their glasses on

I suppose that’s possible.

I have a very early SE. Played about with my new Autel and its reported the SOH as 92% ish on 12k miles.

Not overly worried as there is no way this is a linear progression.

Not miles from mine then. Other than this report I’ve not noticed and difference in range beyond that to be expected in winter.

 

[siteguru]

I had Car Scanner up on the Info display via AA last night when I was heading home. SOH was showing as 92.52%, down from 92.65% last time I checked a few weeks ago.

 

[Romeo77]

I might be wrong but I think that for proper calibration and getting best SOH afterwards calibration done the discharge and charge cycles for that purpose should be performed when battery not colder then 25 degrees Celsius because LFP when its temperature less then 25°C will have higher internal resistance, and will not be able to give its full capacity.
Use the battery heating function to warm the battery from the battery menu.
Discharging low when battery cells not have same temperature and generally colder then 25 degrees Celsius (huge temperature difference across battery cells) will also give wrong result of SOH and will not let all cells get equal charge because of colder cells will quickly get to higher voltage (higher internal resistance when cell cold) and will result in big voltage delta at end of charging and loss of available capacity.
That low SOH might be also because cells are not balanced well for long time.
I found on my car that fast accelerations and high and frequent regen braking adds imbalance also.

 

[fnegroni]

I treat my LFP battery as a fuel tank: fill up to full and keep using until it’s at least 25% or lower, frequently much lower.
I heat the battery before charging when it’s really cold. I heat the battery if I need performance or I stick with ECO power.
I lower the regen to 2 or 1 when it’s below 0 Celsius because of reduced grip.
This is the same as I would on any other car but LFP seems to prefer sitting at different charge levels more.

 

[unbornidentity]

I might be wrong but i think that for proper calibration and getting best SOH afterwards calibration done the discharge and charge cycles for that purpose should be performed when battery not colder then 25 degree Celcius because LFP when it`s temperature less then 25 C will have bigger internal resistance and will not be able to give it`s full capacity.
Use battery heating function to warm battery from battery menu.
discharging low when battery cells not have same temperature and generaly colder then 25 degrees celsius (huge temperature difference across battery cells) will also give wrong result of SOH and will not lett all cells get equal charge because of colder cells will quck get to higher voltage (higher internal resistance when cell cold) and will result in big voltage delta at end of charging and loss of awailable capacity.
That low SOH might be also because cells not balanced well for long time.
Found on my car that fast accelerations and high and frequent regen bracking adds imbalance also.

I’ve wondered if the relatively poor SOH is related to the temperature difference compared to the last time I ran it down below 10%. I expect the battery is fine but it’s just losing track due to the time between now and then and the battery temperature difference. Think it was only about 5 degrees when it had the service. I’d also been down to 15% and only charged to 85% the night before so might have been a bit unbalanced.

Before next years service I’ll get it right down below 10%, preheat the battery, charge to 100% and heat it up before dropping it off. I think it’s probably just an anomaly rather than real degradation. If it’s lost even more health I’ll consider my options that September as it’s on a 3 year 0% PCP. The plan is to keep it but think I could easily be tempted in to a Renault 5!

 

[unbornidentity]

I treat my LFP battery as a fuel tank: fill up to full and keep using until it’s at least 25% or lower, frequently much lower.
I heat the battery before charging when it’s really cold. I heat the battery if I need performance or I stick with ECO power.
I lower the regen to 2 or 1 when it’s below 0 Celsius because of reduced grip.
This is the same as I would on any other car but LFP seems to prefer sitting at different charge levels more.

I rarely run down below about 20% because it doesn’t suit my commute, especially in winter. I’d be uncomfortably close to running out of charge as a round trip uses about 20%. It is also a bit of a PITA putting in big charges as I’ve got solar with a home battery and when Octopus schedules weird long sessions I have to mess around with home battery settings to stop it dumping into the car and/or ending up with a flat home battery in the morning.

 

[Everest]

If it does carry on at the same rate and it’s true though it will get claim level by the time it’s 3.

Not if my guess in this posting is true...
MG4 51kWh LFP Battery Health

I have to mess around with home battery settings to stop it dumping into the car

That sounds like something that can be automated.

 

[Romeo77]

I’ve wondered if the relatively poor SOH is related to the temperature difference compared to the last time I ran it down below 10%. I expect the battery is fine but it’s just losing track due to the time between now and then and the battery temperature difference. Think it was only about 5 degrees when it had the service. I’d also been down to 15% and only charged to 85% the night before so might have been a bit unbalanced.

Before next years service I’ll get it right down below 10%, preheat the battery, charge to 100% and heat it up before dropping it off. I think it’s probably just an anomaly rather than real degradation. If it’s lost even more health I’ll consider my options that September as it’s on a 3 year 0% PCP. The plan is to keep it but think I could easily be tempted in to a Renault 5!

If battery cells only at +3 degrees they loose 8-10% of its available capacity so keepeing battery warmer helps to get more kWh from it and also better charging speed when we need DC charge it.

 

[unbornidentity]

Not if my guess in this posting is true...
MG4 51kWh LFP Battery Health


That sounds like something that can be automated.

Haha, well if they tried something sneaky like that it would become obvious when no battery ever dropped below 70% under the mileage limit and they’d be risking a VW diesel gate type law suit.

I still sort of admire the evil genius of programming a car to recognise when it is being emissions tested and temporarily remapping itself to pass the test.

You can automate it using home assistant apparently but I can’t be bothered to sort that out yet. Probably will do eventually but need to buy things and do loads of research to make it happen!

It’s kinda funny thinking back at reading that link how easily I understood the code. Fair enough it wasn’t complicated but I’ve not written code for ages but read that like I was reading a normal sentence! I’d probably have struggled to write it though