MG5 System Fault - HV Battery Shut Off

[dragon2611]

I had this once, where charging on an Osprey 75Kw charger at a pub having a meal.

I was using Bonnet and it messaged saying the charge was complete. I thought nothing of it, but as we were between courses, I popped out to move the car and make the charger available should someone else need it.

I had no problems unlocking and disconnecting the car and noticed the charge was at 94%. However the car started and moved with no problems. The charge rate averaged out at around 40Kw/hr.

I wonder if the time it took you to notice and get to the charger was long enough for the car to disconnect from the charger then goto sleep/off and thus clear any error.

Whilst I try not to rapid charge to such a high SOC there have been occasions where it's happened on a 50KW charger.

 

[jackois]

I wonder if the time it took you to notice and get to the charger was long enough for the car to disconnect from the charger then goto sleep/off and thus clear any error.

Whilst I try not to rapid charge to such a high SOC there have been occasions where it's happened on a 50KW charger.

It could be, dragon.

This was when I needed the extra range to be sure of reaching my preferred charge point when coming back to Southamptonfrom Leeds. In the last wee while, there's been a marked improvement in the number of good charge stops on this run, so I no longer aim to have the battery at it's fullest on a longer journey.

 

[Eco]

Whilst charging on a Public rapid charger the charge stopped at 94% and when I disconnected, the car was showing a system fault; HV battery shut off
After turning everything off and leaving for 5-10 minutes the car came back on,
Has anybody else encountered this and do they think its a safety mechanism protecting the battery?

I had the same issue. The car afterwards start giving about 115 mile range even after next day 100% charge

 

[smokie]

I went to the tip today. Offloaded the cardboard then got in to move to the wood area (yes, our tip has segregated areas). Tried starting it and got the HV Battery Shut Off error. I've had it before and I've always put it down to having rushed selecting drive mode too quickly after restarting. It usually works on 2nd attempt.

Not today, when I was a bit in the way!! I unloaded the rest of the car manually so probably more than 5 minutes then tried again - no luck. Borrowed a 10mm spanner from the tip man ( - they were really understanding and helpful!!), disconnected -ve for a minute or two then reconnected - no good. Was fiddling with the key while telling the tip man I was about to call the AA and inadvertently locked it. Unlocked it to sit in and make the call and it worked!! I obv got loads of error messages about the Pilot stuff not working etc but they went during the short drive home,. Tried it again at home and it seems fine.

The car was last fully charged on home charger (and left on for balancing) a few days ago and is at about 80%. The 12v gauge says 13.4v. I still think it was probably me being hasty but I called the garage and they will look at the diags for me, but not till 18 Aug (by when it may have been overwritten I guess!).

Is there some way to access diags myself, and if so will it tell me anything? I do have a dongle used with a previous car.

 

[Alb]

You should be able to get some data at least through Car Scanner (what I use).

 

[smokie]

Oh OK, I'll have a look. Thanks.

 

[Caramaddy]

Oh OK, I'll have a look. Thanks.

Please let us know what you find.

 

[PVperson]

It has either to do with main battery temperature or the 12v being low.
It's happened to me once at 95% and same result wait 10 and its fine. My solution is not to rapid charge past about 85%, never had the issue again.

If you run the electrics on 12v during the charge (i.e.not in ready mode) the main battery cannot recharge it and if the voltage drops too low you get the hv batt cut off error. Once charging stops the main battery can supply power to the 12v again.

It happened to me this morning driving 70mph down the M3, LV batt on 13.8V! As soon as I stopped (at a junction) it cut the HV battery. It's something else, you need a tech with the MG software on their laptop to diagnose the fault, I believe it's "catch all" fault, the worst thing thing is is cuts the HV battery, then you can't drive/charge the car.

 

[dragon2611]

There was a dodgy sw version that caused a lot of check hv battery issues but that would throw it into limp mode not kill it totally.

I suspect if the BMS sees a voltage or temp go too far out of threshold it immediately triggers an emergency shutdown and opens the contractors as it’s presumably trying to avoid either damaging the HV battery or a dangerous condition from occurring

 

[MickeySw]

It happened to me this morning driving 70mph down the M3, LV batt on 13.8V! As soon as I stopped (at a junction) it cut the HV battery. It's something else, you need a tech with the MG software on their laptop to diagnose the fault, I believe it's "catch all" fault, the worst thing thing is is cuts the HV battery, then you can't drive/charge the car.

On the advice of others I have kept an emergency kit in my car consisting of a 10mm spanner, OBD dongle and jump starter battery pack, saved me calling the AA twice..

 

[kevin ellard]

On the advice of others I have kept an emergency kit in my car consisting of a 10mm spanner, ODB dongle and jump starter battery pack, saved me calling the AA twice..

Don't put the battery pack in the boot. It will be the most awkward place to get to if the 12V battery goes flat.

 

[PVperson]

On the advice of others I have kept an emergency kit in my car consisting of a 10mm spanner, OBD dongle and jump starter battery pack, saved me calling the AA twice..

Fault still exists, I charged the LV battery to 14.4V yesterday, still not resetting, I have no working car! MG service is booking into December. I have the guy who found the crash sensor problem coming Thursday. I'm an electronics engineer myself, I have an OBDII fault code reader in the car, and it's not even able to access the MG5 comms. (finds nothing) I have tried both "dodges" of disconnecting the battery for 5min, (which has cleared all my trip data again!) and locking the car for 10+min, nothing doing.
Just so your readers understand how ECU's work, if you have a SPURIOUS fault, it may clear, or be cleared by an ODBII terminal, if you have an EXISTING fault, e.g. one that still exists, then you need to fix the fault before clearing the code! in this case, and in the case of airbags gone off, SDM, etc. this will DISABLE THE CAR till it is fixed...
I found that my "MG assistance" expired in January, so I only have the 7-year warranty to go by.

 

[MickeySw]

I have an OBDII fault code reader in the car, and it's not even able to access the MG5 comms. (finds nothing)

Did you manage to connect beforehand when the car was working or is this first time trying?

I have tried both "dodges" of disconnecting the battery for 5min, (which has cleared all my trip data again!) and locking the car for 10+min, nothing doing.
Just so your readers understand how ECU's work, if you have a SPURIOUS fault, it may clear, or be cleared by an ODBII terminal, if you have an EXISTING fault, e.g. one that still exists, then you need to fix the fault before clearing the code!

Very true, but if you can’t connect via OBD, how do you know you have a permanent fault?

 

[emmrecs]

I found that my "MG assistance" expired in January

Since this should be renewed "automatically" by an MG service workshop, is your situation because the service was done by a non-MG garage, or did your dealer "forget"? If it is the latter I think you should be hammering on his door and insisting that he both resolves the fault for you AND renews your MG Assistance. If it is the former, perhaps that is a salutary reminder to all of us to ensure we, and the dealers, follow the rules.

 

[PVperson]

I went to the tip today. Offloaded the cardboard then got in to move to the wood area (yes, our tip has segregated areas). Tried starting it and got the HV Battery Shut Off error. I've had it before and I've always put it down to having rushed selecting drive mode too quickly after restarting. It usually works on 2nd attempt.

Not today, when I was a bit in the way!! I unloaded the rest of the car manually so probably more than 5 minutes then tried again - no luck. Borrowed a 10mm spanner from the tip man ( - they were really understanding and helpful!!), disconnected -ve for a minute or two then reconnected - no good. Was fiddling with the key while telling the tip man I was about to call the AA and inadvertently locked it. Unlocked it to sit in and make the call and it worked!! I obv got loads of error messages about the Pilot stuff not working etc but they went during the short drive home,. Tried it again at home and it seems fine.

The car was last fully charged on home charger (and left on for balancing) a few days ago and is at about 80%. The 12v gauge says 13.4v. I still think it was probably me being hasty but I called the garage and they will look at the diags for me, but not till 18 Aug (by when it may have been overwritten I guess!).

Is there some way to access diags myself, and if so will it tell me anything? I do have a dongle used with a previous car.

You need the latest Vgate iCar Pro Bluetooth 4.0 (BLE) OBD2 Fault Code Reader (Vgate is the make) I found a standard ODBII reader didn't work (no comms) It must be compatible with Saic, etc.

 

[MickeySw]

You need the latest Vgate iCar Pro Bluetooth 4.0 (BLE) OBD2 Fault Code Reader (Vgate is the make) I found a standard ODBII reader didn't work (no comms) It must be compatible with Saic, etc.

For every OBD dongle out there that works with the MG5 (several to choose from) there are a dozen or so that don’t. A compatible dongle then needs to be paired to an app that allows one to read and clear DTCs.

Not much point having one in the car for emergencies if you haven’t tried and tested the procedure beforehand.

Not saying it will fix your problem but I wouldn’t wait until Dec to find out..

 

[dragon2611]

For every OBD dongle out there that works with the MG5 (several to choose from) there are a dozen or so that don’t. A compatible dongle then needs to be paired to an app that allows one to read and clear DTCs.

Not much point having one in the car for emergencies if you haven’t tried and tested the procedure beforehand.

Not saying it will fix your problem but I wouldn’t wait until Dec to find out..

The Generic ELM Clone that uses WI-FI I have could read codes but seemingly not clear them, I've not tried doing that with the Vgate BLE one (I know the BLE one can get SOC data as I've used it with ABRP)

 

[Deleted member 13103]

Not wishing to pee on anyone's chips, and not having it happen after a Rapid charge, AND the dealership supposedly clearing this annoyance at the last service(2yr), I get this happening at least 3 or 4 times a week, I just re-press the start button and all is ready...

 

[dragon2611]

Not wishing to pee on anyone's chips, and not having it happen after a Rapid charge, AND the dealership supposedly clearing this annoyance at the last service(2yr), I get this happening at least 3 or 4 times a week, I just re-press the start button and all is ready...

If the car hasn't engaged the HV battery contactors because you didn't have your foot on the brake when you pressed the button you get a very similar message (I think it might be in a different colour but I'm not 100% on that) and indeed pressing the start button again usually works.

If the message is caused by a failed charging session or something else has upset the car however then pressing the button won't work, and the car is essentially a brick until you can clear the fault condition.

 

[Deleted member 13103]

If the car hasn't engaged the HV battery contactors because you didn't have your foot on the brake when you pressed the button you get a very similar message (I think it might be in a different colour but I'm not 100% on that) and indeed pressing the start button again usually works.

If the message is caused by a failed charging session or something else has upset the car however then pressing the button won't work, and the car is essentially a brick until you can clear the fault condition.

My foot is on the brake as soon as I sit the car, I got used to that behaviour when I drove a Volvo truck, you had to press the footbrake whilst releasing the handbrake to equalise the the air suspension...
The HV Battery warning is always amber in my 5...