Slow charge battery

[Goofy]

Hi MG owners,
I keep getting this statement coming up. It was after quite a few 50kwh charges, but I’ve now only used my granny & 7kwh chargers for the past 6weeks. Should I be concerned & get the battery looked at by my dealer?

 

[Cocijo]

Hello. First thing to do is check your full charge battery voltage. Fully AC charge until MG light goes out. Turn on without foot on brake and all accessories turned off. Should read on the battery info screen, either 449/450v or 454/455v give or take a volt or so. If it is much lower then you may have a bms issue. Make sure that you allow the charge to equalise each time by charging until the MG light goes completely out. ?

 

[Kithmo]

Not a fault, the car is just telling you the battery cells are out of balance, which can happen if you rapid charge too much. Rebalancing is done by slow charging to 100%, granny or 7kW, then leaving the charger connected until the MG badge light goes out altogether. The manual recommends that you do this once a month.

 

[Cocijo]

Yes - good point. It is normal to get full charge battery warning especially if you rapid charge a lot. I‘m not so sure about repeated messages though after you’ve been AC charging and equalising for 6 weeks - maybe this is normal - I don’t rapid charge that often myself. It’s worth checking your fully charged voltage though as it gives a great indication to start from.

 

[Kithmo]

Yes - good point. It is normal to get full charge battery warning especially if you rapid charge a lot. I‘m not so sure about repeated messages though after you’ve been AC charging and equalising for 6 weeks - maybe this is normal - I don’t rapid charge that often myself. It’s worth checking your fully charged voltage though as it gives a great indication to start from.

He says he's been charging on granny and 7kW for six weeks but doesn't say whether he's actually let it equalise the cells.
Many EV owners turn the charger off after the car says charged 100% and are not even aware of the balancing part.

 

[Gomev]

Unless of course they have the bad BMS that doesn't do balancing even if it looks like it is.

 

[Goofy]

Hi Guys, firstly thank you for your responses.
I have completed at 3 granny charges until the charge light has gone out since first getting the slow charge instruction.
I did another last night, this time checking the voltage. I’m only getting 424-427V with a full charge. Yesterday I noted it at 413-418V, & I had about 100 miles left. So I’m not getting the voltages you have stated I should be achieving. Another concern, whilst checking the voltage this morning, & after just having unplugged the car a slow charge instruction illuminated. ??
Does this point to the definite necessity for a dealer service visit for a battery status check & maybe a BMS reset?

 

[WAC 768]

Given the voltages, it will take lots of charges to bring the batteries back and typically when its this low I would expect your dealer to do this for you and provide a loan car in the meantime. For reference and from others I’ve heard of it’s took their dealer over 1 month to do this..

 

[Goofy]

Would I be correct to surmise that because of the lower voltage, the actual range will not be what I should achieve?

 

[Lovemyev]

Would I be correct to surmise that because of the lower voltage, the actual range will not be what I should achieve?

That is correct !.
If your pack is affected by the "Buggy" software, then your actual range will be reduced.

 

[Goofy]

You stated the “Buggy” software. Is this something that is known about?

 

[rbpasapera]

You stated the “Buggy” software. Is this something that is known about?

Take a look at this podcast about duff BMS and voltage.

MG EVs special podcast: All your MZ ZS EV BMS Bug Frequently Asked Questions ANSWERED

In the latter part of 2020, some MG ZS EVs had a software version installed which contained a bug which caused the batteries to become imbalanced. In this interview, Miles Roberts will answer the questions that the MG EVs community have about this software update. 00:00:00 - Introduction...

www.mgevs.com

 

[WAC 768]

Would I be correct to surmise that because of the lower voltage, the actual range will not be what I should achieve?

Yes, the range will be much less due to the battery voltage.

 

[Goofy]

Thanks for that!! Explained everything, my car is one that needs the BMS update. Will be calling my dealership in the morning.

 

[Mg4me]

Take a look at this podcast about duff BMS and voltage.

MG EVs special podcast: All your MZ ZS EV BMS Bug Frequently Asked Questions ANSWERED

In the latter part of 2020, some MG ZS EVs had a software version installed which contained a bug which caused the batteries to become imbalanced. In this interview, Miles Roberts will answer the questions that the MG EVs community have about this software update. 00:00:00 - Introduction...

www.mgevs.com

I know this is an old thread, but my MG ZS EV my22 clearly has the BMS issue. I've been noticing how long it takes to charge. It only reaches 11kwh on a 22kwh charger. On a 50kwh charger, I might see it peak at 35kwh. So for now, I cannot reasonably go on any longish trip. It takes 4 hours to charge from empty to full on 22kwh, and around 2hrs on 50kwh. I'll watch the podcast and see what they say.

 

[Cocijo]

I know this is an old thread, but my MG ZS EV my22 clearly has the BMS issue. I've been noticing how long it takes to charge. It only reaches 11kwh on a 22kwh charger. On a 50kwh charger, I might see it peak at 35kwh. So for now, I cannot reasonably go on any longish trip. It takes 4 hours to charge from empty to full on 22kwh, and around 2hrs on 50kwh. I'll watch the podcast and see what they say.

The onboard charger limits AC charging to 11kw no matter what the charge point provides. It’s rarely possible to get the full DC charge rate unless all conditions are met. It doesn’t sound like your car is performing any different to the way it should. When you get to around 80% DC charging will slow right down so most will only DC charge to 80% and move on.

 

[Lovemyev]

I know this is an old thread, but my MG ZS EV my22 clearly has the BMS issue. I've been noticing how long it takes to charge. It only reaches 11kwh on a 22kwh charger. On a 50kwh charger, I might see it peak at 35kwh. So for now, I cannot reasonably go on any longish trip. It takes 4 hours to charge from empty to full on 22kwh, and around 2hrs on 50kwh. I'll watch the podcast and see what they say.

The pod cast is aimed more at the BMS issues on the ZS EV ( Gen 1 ) TBH.
As it appears that you have the ( Gen 2 ) then it’s not really relevant.

 

[Nisar]

I know this is an old thread, but my MG ZS EV my22 clearly has the BMS issue. I've been noticing how long it takes to charge. It only reaches 11kwh on a 22kwh charger. On a 50kwh charger, I might see it peak at 35kwh. So for now, I cannot reasonably go on any longish trip. It takes 4 hours to charge from empty to full on 22kwh, and around 2hrs on 50kwh. I'll watch the podcast and see what they say.

Yes my MG have been doing the same but now it got too slow on 50 KWH it runs on 14 KWH only, So not sure how to fix, called dealer but they gave me booking after 4 weeks and going to take a whole day to diagnose it. Any brilliant idea to fix it at home ?

 

[DB Go Rex]

Yes my MG have been doing the same but now it got too slow on 50 KWH it runs on 14 KWH only, So not sure how to fix, called dealer but they gave me booking after 4 weeks and going to take a whole day to diagnose it. Any brilliant idea to fix it at home ?

Have you left it to balance charge at home? (leave it on charger at 100% until power drops off).