HV battery failure

[Dodger]

I keep an adjustable spanner in the car when i'm out and about in case i have to disconnect the battery, tighten the steering column, remove and refit the sunroof or take the motor out!

 

[Reggie 838]

Disconnect the Negative lead on the 12 volt battery ( if you have a 10mm spanner ) leave for a few minutes, then reconnect the negative terminal.
This has be seen by other owners on the forum !.
I am sure the RAC man will do this hard reset when he arrives !.
Good Look !.
Hands up how many members now carry a 10mm spanner in their cars ?.
I have put a cheap 10mm spanner in a resealable plastic bag, and taped it to the side of the 12 volt battery.
Just try and cover all bases really.
Having a space wheel a 12 Volt booster pack and a 10mm spanner offers some type of back up plan.
If these items fail, it's a ride home on a flat bed !.

Hi thanks for that. That was the first thing the RAC man did. Sorry to say it did not work but I will now add a 10mm spanner to my toolkit. It has gone away on the back of a recovery vehicle to MG.

I have seen quite a few suggestions. The one that I would of like to seen before the RAC man left was to log into the diagnostics and clear the error codes.
But alas I will let the MG sort it out.

 

[Lovemyev]

Hi thanks for that. That was the first thing the RAC man did. Sorry to say it did not work but I will now add a 10mm spanner to my toolkit. It has gone away on the back of a recovery vehicle to MG.

I have seen quite a few suggestions. The one that I would of like to seen before the RAC man left was to log into the diagnostics and clear the error codes.
But alas I will let the MG sort it out.

Is the car completely dead altogether @Reggie 838 .
Can I throw another suggestion / cause into the mixing pot please ?.
I just wonder if it has blown the main H.V. fuse that protects the pack.
There have been a few reports of this happening.
The dealer I used for my first service had seen two cars hit by this condition.
One car was delivered on a flat bed to the dealer and the second one car died while having it's PDI checks prior to delivery to a new customer !.
Both cars where shipped out to another much bigger dealer to sort the problem.
As a result of these failures MG have released a service bulletin ( S017 If I remember correctly ) that advises the dealers to apply a software update to correct the problem.
It maybe dealt with on a VIN number basis.
Please keep us posted on your progress.

 

[Kithmo]

I wonder what it is that actually blows the HV fuse, is it a high charging rate or something ?

 

[Lovemyev]

I wonder what it is that actually blows the HV fuse, is it a high charging rate or something ?

I have no idea @Kithmo.
One car at my local dealer decided to blow the main HV fuse on the PDI check.
Even it failed while on charge, it would only been on a 7.0 kw wall box.
Interesting though, that on the new BMS update ( 15th Jan 2021 ) that the reported voltage on the HV pack after a full charge, has been reduced from the original 456 volts on the original OEM software and now been pulled down to 448 / 450 volts ?.
It could have NO connection what so ever of course !.
On the MG SO17 service bulletin, it does instruct the dealer to apply the HV fuse protection update at the first opportunity.
Either a bad batch of fuses or they have reduced the load passing through this fuse to prevent overload it ??????.

 

[JodyS21]

Had my BMS update this week. On collecting the car I asked for a copy of my digital service record. Was informed that there is nothing recorded on it as it had not been serviced yet. So in short it looks like MG don't know what sw is on your car. But how did they create the recall list for the faulty BMS?

List safely stored on server in China ???

They must have data from every car - the software versions, saved on a Chinese server. But I guess they don't consider this part of the service information and more so they want to keep it hidden/not for customers to see.
Would be interesting to put in one of those freedom of information requests for all data related to you/your car.....

 

[JodyS21]

Second rapid charge. RAC stumped and waiting for the tow lorry. Funny the car will of done more miles on the back of a recovery truck than on the road great range from a single charge.

That is one way to get awesome Miles per kWh.....

 

[Goofy]

Well, I’m pleased to be able to say my dealership-Masters Group Croydon has got me up & running again. ?
However I couldn’t afford it leave it with them to complete the re-balancing of the batteries. I’m going to be doing this by putting it on my granny charger every night & allow it the 2-3 hours balancing it should now be doing following a full charge.
Although, I’m a little perturbed as this morning when I checked the voltage achieved - only 427v ? which I understand should increase in time to the 450v , I also got the same fault code “slow charge the battery” Is this to be expected, because the voltage is low? I’m concerned that it’s a fore warning of another HV battery shut down ?

 

[Chrispydoc]

I have a 10 MM spanner taped near the battery on both my MG and PHEV.

The MG ..as described...and the PHEV as it gets so little use, it keeps throwing up daft servicing messages.

Regarding battery balancing, I tend to leave my plugged in after use and often see it "balancing" for several hours...then I unplug it.

My predicted GOM range has remained very consistant at about 175 miles (last 16 months) ...and driven steadily, it will actually do it!

 

[Davemac278]

Well, I’m pleased to be able to say my dealership-Masters Group Croydon has got me up & running again. ?
However I couldn’t afford it leave it with them to complete the re-balancing of the batteries. I’m going to be doing this by putting it on my granny charger every night & allow it the 2-3 hours balancing it should now be doing following a full charge.
Although, I’m a little perturbed as this morning when I checked the voltage achieved - only 427v ? which I understand should increase in time to the 450v , I also got the same fault code “slow charge the battery” Is this to be expected, because the voltage is low? I’m concerned that it’s a fore warning of another HV battery shut down ?

I think you should have insisted on the dealer giving you a courtesy car whilst they carry out the charging as per MG memo. They can claim the cost back from MG as it was due to duff BMS update.

It will take a long time to get your battery up to 449v. I suspect like mine it took over 9 hours just to complete a balance. I'm lucky I'm at 449v and balance time down to 2 hours but my cell imbalance is still out by 20mv.

 

[Lovemyev]

So, did it completely fail to boot up because the battery was so far out of balance then ?.
Caused by the “Buggy” software I suspect.
Yeah - It’s shame you had to bring the car away, because it is going to take you a good while to get your HV pack back to some type of normal.
If you have a secure garage, you could do what the dealer would do and leave it in ready mode overnight and then recharge the pack.
This will speed up the process a little.

 

[JodyS21]

Well, I’m pleased to be able to say my dealership-Masters Group Croydon has got me up & running again. ?
However I couldn’t afford it leave it with them to complete the re-balancing of the batteries. I’m going to be doing this by putting it on my granny charger every night & allow it the 2-3 hours balancing it should now be doing following a full charge.
Although, I’m a little perturbed as this morning when I checked the voltage achieved - only 427v ? which I understand should increase in time to the 450v , I also got the same fault code “slow charge the battery” Is this to be expected, because the voltage is low? I’m concerned that it’s a fore warning of another HV battery shut down ?

It won't be balancing for 2-3 hours after it's charged full, if you're that far out, it'll balance for 10 hours (max) at a time. You're going to need something like 230 hours of balancing to get those missing 23 volts back

 

[Goofy]

I’m guessing that the voltage difference was the reason why the battery did a complete shutdown, but as many have stated one is never told by the dealership.
Yes it’s going to be a while before I see the desired 450v….but up 1v on yesterday to 428v, so heading in the right direction ??

 

[Mark Holmes]

I’m guessing that the voltage difference was the reason why the battery did a complete shutdown, but as many have stated one is never told by the dealership.
Yes it’s going to be a while before I see the desired 450v….but up 1v on yesterday to 428v, so heading in the right direction ??

At least it’s recovering in the potentially warmer months where the lost range will not be perhaps as noticeable until your battery is back up to the correct levels...

 

[mj224]

I’m guessing that the voltage difference was the reason why the battery did a complete shutdown, but as many have stated one is never told by the dealership.
Yes it’s going to be a while before I see the desired 450v….but up 1v on yesterday to 428v, so heading in the right direction ??

Before the January update, my fully charged voltage was 438 volts. It had taken a couple of months of charging and balancing to bring it up to 449 volts. Range is better, in the region of 170 miles or so, and with summer temperatures (we hope) I expect that to increase slightly..

 

[Goofy]

So taking into account that it took your car to gain 10 volts in 2 months, I’m going to be looking at 4 months to get mine up to the full voltage…..I didn’t expect it to take that long ?

 

[JodyS21]

So taking into account that it took your car to gain 10 volts in 2 months, I’m going to be looking at 4 months to get mine up to the full voltage…..I didn’t expect it to take that long ?

It's the amount of time actually balancing that is the factor.
If you use the car every day for at least say 20miles (<93%SOC) then full AC charge and get 10 hours balancing in each night, then you'll get all your necessary balancing done in roughly 23 days....in theory

 

[Goofy]

That’s what’s I was working on too, but I’m not sure if it’s doing a 10 hour balance? Each morning so far the stead light showing it is balancing is out. So complete? I am however hopeful that I will see 450v one morning, cause I love my MG EV ?

 

[Dave53]

I keep an adjustable spanner in the car when i'm out and about in case i have to disconnect the battery, tighten the steering column, remove and refit the sunroof or take the motor out!

???

 

[Lovemyev]

That’s what’s I was working on too, but I’m not sure if it’s doing a 10 hour balance? Each morning so far the stead light showing it is balancing is out. So complete? I am however hopeful that I will see 450v one morning, cause I love my MG EV ?

I believe when the car will get too around 10 hours of trying to balance the pack, it will call "Time Out" and give up and stop.