Faulty battery

[AminurR]

My car went in twice to MG. they update software say problem solved but after I use rapid charge same happens again.
It is ok with slow charge.
MG haven’t given me any report on both times i when taken it in to be checked.

what could be problem?
I go away on holiday in a week

 

[Les burrows]

Hi are you sure you are starting the car in the correct Way I have seen this kind of reading on the dash when I have pressed the start button but not had my foot on the foot brake so turn off again wait a few seconds press the brake now switch on again hope this might help
Les

 

[Jomarkh]

Hi, i wouldn't take the charge to anywhere near 90% on a rapid charger.
Have you tried Turn the car off, get out lock it up for 10 minutes and try again.
Is your 12v battery always showing under 13v ?

 

[AminurR]

Hi are you sure you are starting the car in the correct Way I have seen this kind of reading on the dash when I have pressed the start button but not had my foot on the foot brake so turn off again wait a few seconds press the brake now switch on again hope this might help
Les

This seems to happen when I am using the rapid charge. It charges upto 95% then shuts off and the sign comes up.

 

[5teep]

Yep, really need more info on what your problem actually is. I get that hv battery cut off all the time when as said above I press the start button without my foot on the break.

This seems to happen when I am using the rapid charge. It charges upto 95% then shuts off and the sign comes up.

Ah, this is a common issue. I've had it once when the charge got to 95%. Not sure if it's because your 12v battery gets low or because the main batt overheats. Wait ten minutes and the car starts ok makes me think it might be the 12v battery going low and the main batt charging it back up.
Again as said above don't charge to 95 on rapid, i tend to go for 80-85%

 

[Jomarkh]

How often do you balance the battery using a 7.5kw or granny charger?

 

[Les burrows]

I have to agree with the posts above about charging past 80-85% not a good thing to be doing really on a rapid charger also while you are charging are you using the HVAC or the radio or something else if so this could run down the 12 volt battery in no time at all
Les

 

[Petriix]

There's almost certainly an issue with the rapid charging software in the car. Unsurprising when you realise how buggy the AC charging is. It might be as simple as the 12v battery getting depleted but I suspect it's a bigger issue.

We need to compile some information to help us avoid recreating the same circumstances. I keep asking the same questions but don't think I've had answers:

1. Which charger was it
2. Was the car in 'ready' or accessories mode?

 

[Lovemyev]

How often do you balance the battery using a 7.5kw or granny charger?

MG recommend once a month.

 

[LeoRBK]

My car went in twice to MG. they update software say problem solved but after I use rapid charge same happens again.
It is ok with slow charge.
MG haven’t given me any report on both times i when taken it in to be checked.

what could be problem?
I go away on holiday in a week

You have to insist for a report of the work carried out. You can still ask dealer to provide reports as they are digitally stored in MG database.
The battery has built in protection which kicks in under certain circumstances. The protection seems to isolate tthe HV battery for some time(suspected to be approx 10 mins).
As others have indicated switching off for approx 10 mins, locking and walking away outside the range of keyless system seems to do the trick for some members.

Suspect scenarios,
1. Long motorway drive on a hot day + Rapid charge cause very hot battery
2. A really long rapid charge session on a hot day
3. Car does not like the rapid charger. There can be misunderstandings between rapid charger and the car sometimes leading to this behaviour.

If urgent, people are able to recover quickly from the situation by disconnecting & reconnecting 12 V battery, effectively resetting the car and clears the error code stored in the car.

Last resort which you probably already tried is call AA and dispatch to MG dealer.

Personally I think it would be better if the error message were this " HV Battery shutoff, please try after 10 mins".

Since you are close to holiday and probably will not have another diagnosis, can I suggest, avoid running down the battery to low and then charging it back to high percentage on rapid. Instead, plan more breaks in your journey with shorter top up sessions on rapids.

Carry a 10mm spanner in car to reset as described before if nothing else works.

 

[5teep]

When it happened to me it was close to the scenario Leo describes. Very hot day and had the ac on so that each time I powered up to check charge it drained the 12v battery a bit more.
It seems stupid to me that you have to power on and then off again to see the charge state info (or get out and check the charger). If we had a working app the situation would not arise.

 

[Frank]

The fear of using a RAPID Charger to charge to 100% is unfounded and if you have the time or need to charge to 100% and you are not holding up a queue then carry on.

My reasons for this are as follows:-

a. The only reason why all manufacturers only quote charge times to 80% is because they know that their BMS systems kick in reducing the charge level and therefore if they quoted to 100% it would look unnecessarily long.
b. Once the BMS has reduced the level you are NOT RAPID charging, so crack on you are not damaging the battery.
c. I can't understand why so many are IMO so concerned about the battery whilst under cover of warranty.
d. Historically it has been proved by statistics that battery health over time has been far better than expected.
e. Manufacturers do NOT want warranty claims on very expensive components so design their BMS (usually!!!) accordingly.
f. Lastly, nothing to do with RAPID charging but if you have a home charger, use it, I have plugged in my last 3 EVs every night no matter what the state of charge and have NEVER had any problems with balancing or 12v battery problems.

 

[Petriix]

The fear of using a RAPID Charger to charge to 100% is unfounded and if you have the time or need to charge to 100% and you are not holding up a queue then carry on.

My reasons for this are as follows:-

a. The only reason why all manufacturers only quote charge times to 80% is because they know that their BMS systems kick in reducing the charge level and therefore if they quoted to 100% it would look unnecessarily long.
b. Once the BMS has reduced the level you are NOT RAPID charging, so crack on you are not damaging the battery.
c. I can't understand why so many are IMO so concerned about the battery whilst under cover of warranty.
d. Historically it has been proved by statistics that battery health over time has been far better than expected.
e. Manufacturers do NOT want warranty claims on very expensive components so design their BMS (usually!!!) accordingly.
f. Lastly, nothing to do with RAPID charging but if you have a home charger, use it, I have plugged in my last 3 EVs every night no matter what the state of charge and have NEVER had any problems with balancing or 12v battery problems.

Fair enough if you aren't bothered about the marginal gains but it's objectively wrong to suggest that rapid charging at high states of charge won't damage the battery. All charging and discharging damages the battery and the higher the current and the further from the mid voltage range the greater the damage. It's miniscule but insidious.

The warranty is for 70% capacity. That's an enormous drop in range which would be pretty painful. Instead of 140 miles on the motorway in winter you'd be getting 98. Given yourself a 20 mile buffer and only running 90%-20% you're looking at under 70 miles per leg in the worst conditions.

Calendar degradation alone will typically reduce capacity by 3% per year, maybe more in the first year. Much of this will be hidden by the buffers at either end of the battery so you probably won't start to notice it for a while. Personally I prefer to take the simple steps to limit the degradation as much as possible. Do what you like with your own car, but don't spread misinformation.

 

[Petriix]

When it happened to me it was close to the scenario Leo describes. Very hot day and had the ac on so that each time I powered up to check charge it drained the 12v battery a bit more.
It seems stupid to me that you have to power on and then off again to see the charge state info (or get out and check the charger). If we had a working app the situation would not arise.

Are you pressing the power button without your foot on the brake? If you do that then you will quickly flatten the 12v battery, especially if the aircon is on. I know that the manual says not to, but you have to switch to full 'ready' mode to keep the 12v battery topped up.

 

[5teep]

Are you pressing the power button without your foot on the brake? If you do that then you will quickly flatten the 12v battery, especially if the aircon is on. I know that the manual says not to, but you have to switch to full 'ready' mode to keep the 12v battery topped up.

Sometimes yes and still do though now I switch off again immediately when I checking soc.
This happened to me on my 2nd day of driving the car and only my third charge. I do 1000 miles a week in it and have charged maaaaany times since without issue having learned my lesson.

 

[Lovemyev]

Calendar degradation alone will typically reduce capacity by 3% per year, maybe more in the first year. Much of this will be hidden by the buffers at either end of the battery so you probably won't start to notice it for a while.

I agree .

 

[Frank]

Fair enough if you aren't bothered about the marginal gains but it's objectively wrong to suggest that rapid charging at high states of charge won't damage the battery. All charging and discharging damages the battery and the higher the current and the further from the mid voltage range the greater the damage. It's miniscule but insidious.

The warranty is for 70% capacity. That's an enormous drop in range which would be pretty painful. Instead of 140 miles on the motorway in winter you'd be getting 98. Given yourself a 20 mile buffer and only running 90%-20% you're looking at under 70 miles per leg in the worst conditions.

Calendar degradation alone will typically reduce capacity by 3% per year, maybe more in the first year. Much of this will be hidden by the buffers at either end of the battery so you probably won't start to notice it for a while. Personally I prefer to take the simple steps to limit the degradation as much as possible. Do what you like with your own car, but don't spread misinformation.

First of all I never said that RAPID charging is not bad for the battery , it is, but when the BMS throttles back the charging level it will revert to a level that is not damaging.

I would advise anyone if possible NOT to RAPID charge at all but when it is unavoidable and for what ever reason you want to take a full charge from a RAPID Charger then do so for the reasons I already mentioned.

I am not spreading misinformation , we all know that when the BMS throttles back the charging level it is really slow probably equivalent to a 7kwh home charger or less.

In summary don't RAPID charge unless you have to but also if needed don't be too concerned about taking a full charge if circumstances require you to do so. Any significant degradation to the battery will happen from starting charging up to when the BMS feels the need to kick in and not after that.

Lastly none of the so called experts can agree on the ultimate charging regime, but they all agree on one thing RAPID charging has the GREATEST effect on the degradation of the battery which is a bit of a shame as that is the only viable charging method (currently) when on journeys greater than the range of your car.

 

[SimonomiS]

When it happened to me it was close to the scenario Leo describes. Very hot day and had the ac on so that each time I powered up to check charge it drained the 12v battery a bit more.
It seems stupid to me that you have to power on and then off again to see the charge state info (or get out and check the charger). If we had a working app the situation would not arise.

Assuming the car is locked you can press the button on the door handle while charging and the display (only) will wake up and show the charge status - there's no need to power on and off again. Some chargers (Osprey f.ex) show the SOC on their app while you're away from the car.

 

[Petriix]

First of all I never said that RAPID charging is not bad for the battery , it is, but when the BMS throttles back the charging level it will revert to a level that is not damaging.

I would advise anyone if possible NOT to RAPID charge at all but when it is unavoidable and for what ever reason you want to take a full charge from a RAPID Charger then do so for the reasons I already mentioned.

I am not spreading misinformation , we all know that when the BMS throttles back the charging level it is really slow probably equivalent to a 7kwh home charger or less.

In summary don't RAPID charge unless you have to but also if needed don't be too concerned about taking a full charge if circumstances require you to do so. Any significant degradation to the battery will happen from starting charging up to when the BMS feels the need to kick in and not after that.

Lastly none of the so called experts can agree on the ultimate charging regime, but they all agree on one thing RAPID charging has the GREATEST effect on the degradation of the battery which is a bit of a shame as that is the only viable charging method (currently) when on journeys greater than the range of your car.

You are spreading misinformation because you suggest that there is a level of charging which is 'not damaging'. I suspect that you actually mean 'less damaging' but all charging and discharging causes some degradation.

I'm not advising people to never rapid charge, but I do advise discretion on rapid charging above 85%. Mostly this is because it's a waste of time as the total journey would normally be quicker with a second stop: 15% added between 30-45% would take 10 minutes; between 85-100% it takes 30 minutes.

The MG5 also seems to have a rapid charging issue at 93-95% so I'd definitely avoid going that high.

Obviously people need to use their vehicles as required. No one is suggesting sacrificing range to protect the battery. It's just that simple steps can act to reduce overall degradation in the medium to long term. Suggesting that there's absolutely nothing to be gained by using discretion is misleading.

 

[Lovemyev]

but all charging and discharging causes some degradation.

I totally agree, this is a fact that can not be avoided, but only as we know the regular use of rapid units will increase the degradation.
But when making longer journeys, it has to be accepted unfortunately.
When you need to charge, you need to charge I guess !.
Charging above 80% will slow down your progress because the rapid will start throttling back the charge rate heavily at this point.
Better to stop the charge at around 80% and move on.
My car is 18 months old and has covered almost 14,000 happy miles.
It has only been subjected to three small splash and dash charges in that time.
The remainder of our charging is carried out from out home wall box.
The car received the latest BMS update in Jan 2021 and now reports 448 - 449 volts after a full charge and balance and reports a pretty consistent 156 - 157 miles of range in the default mode.
So, I do truly believe there is a small amount of degradation in then.
It did report a range of 162 - 163 after the car was updated, but this has decreased slightly over time.
These figures are taken in the correct way by resetting the trips etc.
Battery degradation is a fact of life in an EV as we all know.
You can help with its SOH by avoiding the prolonged use of rapids, but you can not eliminate it - fact !.