2021 MG5 Battery Care

[Paul Hampshire]

Hi, I have recently acquired a 2021 MG5 with 50k miles. Battery health 94% according to garage check / certificate when i bought it. Typical max range 200 - 205 miles so far. Will be almost always charged up at home on 7kW charger.

How often should I charge to 100% (instead of 80%) charge to properly do the "Equalisation" process....monthly? I gather than when get to 100% need to leave it on charger for a few hours to properly complete the Equalisation process. How many is "a few" - anyone got any views on this please? Thank you.

 

[Jomarkh]

Hi, I charge my two MG5'S to 80-90% and on an Octopus green energy night to 100% monthly or there abouts. If you do it regularly then it does take much longer once it reaches 100%

 

[MickeySw]

The MG5 (FL) user manual states the following:

“When using the vehicle on a daily basis, it is recommended to fully charge it at least once a week, which is conducive to the health maintenance of the high-voltage battery pack; every 3 months to half a year, a low-power (less than 10% or 1 grid) full charged is performed.”

MG’s recommendation seems to be is to balance charge once a week and to re- calibrate the BMS about three times per year.

 

[Paul Hampshire]

The MG5 (FL) user manual states the following:

“When using the vehicle on a daily basis, it is recommended to fully charge it at least once a week, which is conducive to the health maintenance of the high-voltage battery pack; every 3 months to half a year, a low-power (less than 10% or 1 grid) full charged is performed.”

MG’s recommendation seems to be is to balance charge once a week and to re- calibrate the BMS about three times per year.

Thanks Mickey, much appreciated. To clarify:

1/. Mine is an NMC battery not an FLP one - does the above advice apply to NMC? (I note the "FL" in brackets at the start of your comment).

2/. Most advice seems to be to use / charge between 20% and 80% capacity routinely and then every (say) 4 - 6 weeks to fully charge to 100% and leave it a few hours after then to let it fully rebalance. This seems to be different to what you are saying?

3/. What is the "BMS" you refer to please?

Again thank you Mickey, hope its ok to ask these follow-on questions...!

Cheers, Paul

 

[Gomev]

Hi, I have recently acquired a 2021 MG5 with 50k miles. Battery health 94% according to garage check / certificate when i bought it. Typical max range 200 - 205 miles so far. Will be almost always charged up at home on 7kW charger.

How often should I charge to 100% (instead of 80%) charge to properly do the "Equalisation" process....monthly? I gather than when get to 100% need to leave it on charger for a few hours to properly complete the Equalisation process. How many is "a few" - anyone got any views on this please? Thank you.

As aften or as little as you want or is convenienent.
Leave it as long as you can, once it's done it won't come to any harm if it's still plugged in. It also won't come to any harm if you unplug it while it's still balancing.
The more often you do it the quicker it is. Could be less than 10 minutes, could be an hour or more, depending on how long between.
Key part is though, don't lose sleep over it.

 

[Pete G]

Hi Paul, the BMS is the battery management system electronics. It checks each cell and makes sure that they are all charged to the same level.
Pete

 

[MickeySw]

Thanks Mickey, much appreciated. To clarify:

1/. Mine is an NMC battery not an FLP one - does the above advice apply to NMC? (I note the "FL" in brackets at the start of your comment).

FL relates to the ‘face lift’ model, yours is it’s predecessor although it’s using the same battery system (NMC chemistry)

2/. Most advice seems to be to use / charge between 20% and 80% capacity routinely and then every (say) 4 - 6 weeks to fully charge to 100% and leave it a few hours after then to let it fully rebalance. This seems to be different to what you are saying?

I’m merely quoting the manual which suggests to do a balance charge once a week and a deep discharge (10%-100%) to re-calibrate the BMS (SoH) every couple of months.

That said, I generally run within the 40-70% range most of the time and only charge to 100% (and leave it plugged in) when I need the extra range (about once a month). Never felt the need to re-calibrate the BMS.

Modern NMC cells are will outlive the rest of the car, as long as you don’t leave your EV sitting fully charged or empty for weeks on end SoC range used is irrelevant.

3/. What is the "BMS" you refer to please?

As already mentioned by @Pete G

 

[emmrecs]

@Paul Hampshire

You do need to be aware that with the pre-facelift MG5 there is no method to limit the charge to 80% other than manually turning off the charger at the appropriate time! The FL (facelift) version does include that facility, via the iSmart app and the car itself.

 

[Adee]

I'm not sure if my approach is of interest/value. But I charge almost every night using a "granny" charger (2kV approx) and a 7hr mains timer almost regardless of the existing charge level. Hence it is frequently charged up to 100%. Based on the % charge drop in the first few miles I would estimate that the battery capacity/range is somewhere around 96-97% of when it was new. It is currently 5yrs old and has 66k miles on it. I wonder if people worry too much about charging regimes or maybe I have just been lucky (or maybe low charge rates are more beneficial). I have only ever once charged the car away from home - probably 50kV type charger.

 

[MickeySw]

Based on the % charge drop in the first few miles I would estimate that the battery capacity/range is somewhere around 96-97% of when it was new.

You’re probably not far off, not because of your method rather than that’s what one would expect given the particulars.

If you want to know exactly, next time you charge to 100% reset the trip counters, range in ‘Normal’ mode (nor ECO or Sports) displayed is WLTP - degradation, e.g. for LR 250 miles -> 100% SoH, 237 miles -> 95% SoH.

I wonder if people worry too much about charging regimes or maybe I have just been lucky (or maybe low charge rates are more beneficial). I have only ever once charged the car away from home - probably 50kV type charger.

You’re right, apart from leaving an EV either fully charged or completely empty for weeks on end ones ‘charging regime’ doesn’t make much of a difference for battery life, the vast majority (all?) of MG5s sold still have a SoH >90% and their battery will probably outlive the car…

 

[m4rmite]

If you want to know exactly, next time you charge to 100% reset the trip counters, range in ‘Normal’ mode (nor ECO or Sports) displayed is WLTP - degradation, e.g. for LR 250 miles -> 100% SoH, 237 miles -> 95% SoH.

Is that accurate though?
I ask as when I charge my SR PFL to 100% I can get anywhere from 209-219 miles instead of 214. Doesn't it depend on how economically you've driven it beforehand?

 

[Pete G]

The range will also depend on ambient temperature.
Our Gen 1 ZS gets around 254 kilometres range in summer when the ambient is around 25 degrees C. Then in winter when the ambient is under 10 degrees C the range is around 240 kilometres.
Pete

 

[Gomev]

Is that accurate though?
I ask as when I charge my SR PFL to 100% I can get anywhere from 209-219 miles instead of 214. Doesn't it depend on how economically you've driven it beforehand?

That's why you reset the accumulated trip meter which cancels the previous driving data. It is accurate.

As per the instructions @MickeySw gave.
Charge to 100% and allow to balance.
Switch on to Ready
Reset accumulated trip, (or all)
Select Normal driving mode.
View GOM
Calculate

 

[AndyB87]

How often should I charge to 100% (instead of 80%)

I tend not to worry about it, I work shifts - so on my 4 days in, the car gets charged to 100% each night at just under 7kw via home charger. Then on my last day I leave the car at the 50% (ish) that I got home with and only top up if we're off out somewhere. My battery SOH is at 95.6% at 41k miles. Was at 96.8% when I bought it with 21k miles on the clock (2021 pfl). But all the cells are balanced, as when using the obd to check the battery health, it shows the Min/Max voltage values for each bank of batteries.

 

[reg10]

when i had mine serviced and mot ready for my lad to have they told me the battery was 100%
we charge when needed over night but every couple of months we use the 3pin plug to charge
34,000 mile done

 

[MickeySw]

My battery SOH is at 95.6% at 41k miles. Was at 96.8% when I bought it with 21k miles on the clock (2021 pfl). But all the cells are balanced, as when using the obd to check the battery health, it shows the Min/Max voltage values for each bank of batteries.

That’s sound about right, degradation isn’t linear, it tends to slow down after the initial drop of SoH.

Curious what do you get for min/max values?

 

[AndyB87]

That’s sound about right, degradation isn’t linear, it tends to slow down after the initial drop of SoH.

Curious what do you get for min/max values?

Not sure I've ever checked when the battery has been at 100% charge. Im sure the maximum they reach is around 3.6v but im not certain of that. All I know is that 3 modules have a 0.01v difference in the min max values and the rest have zero difference.

 

[MickeySw]

Not sure I've ever checked when the battery has been at 100% charge. Im sure the maximum they reach is around 3.6v but im not certain of that. All I know is that 3 modules have a 0.01v difference in the min max values and the rest have zero difference.

Ok, looks like you’re using CarScanner; the app’s ‘CMUXXX’ values don’t make much sense (i.e. a fully charged cell is around 4.2V).

What seems to be accurate though are ‘Battery Cell Min/Max Voltage’, what do they read?

 

[AndyB87]

Ok, looks like you’re using CarScanner; the app’s ‘CMUXXX’ values don’t make much sense (i.e. a fully charged cell is around 4.2V).

What seems to be accurate though are ‘Battery Cell Min/Max Voltage’, what do they read?

Yes mate, i did realise that when I first started using it as the module voltages never totalled 405v, but i use it more for reference than anything else. Currently the modules are reading Min 3.22v Max 3.22v cell voltage and 3 modules are reading Min 3.22v Max 3.23v. So, well balanced.

 

[MickeySw]

Yes mate, i did realise that when I first started using it as the module voltages never totalled 405v, but i use it more for reference than anything else. Currently the modules are reading Min 3.22v Max 3.22v cell voltage and 3 modules are reading Min 3.22v Max 3.23v. So, well balanced.

A MG5 (NMC) battery consist of 6 modules with 16 cells each, making it a 96S1P pack.

What CarSanner’s ‘CMU1 to CMU24’ -data actually relates to is therefore anyone’s guess?