HV Battery Shutdown

[Rusty168]

The fault - sudden loss of power and rapid deceleration as you desperately try and get to the hard shoulder. It might coincide with being in cruise and then braking.

Car needs to come to a full stop. Place in park. Foot on brake and car says ready and power is restored

I have had the car for three months. The car had this fault three times in the first two weeks. AA disconnected battery and fault seemed to stop. Happened a fourth time and took it into MG who updated the software. Just happened for a fifth time so it's not fixed.

Very dangerous. Has anyone else had this fault or had it resolved?

 

[Rolfe]

Crikey, no! That's a bad one. It doesn't sound like any of the other power loss complaints, which have been a lot less dramatic.

 

[Grriff]

Sounds terrible and very dangerous.
You wrote that the AA reconnected the battery so I presume the 12V battery terminals are secure?

 

[SarahT]

@Rusty168 exactly the same thing happened to me yesterday. Had the EV4 for 2 months, driving on a busy A road with my family in the car, I braked gently and suddenly the car power went, a message flashed up saying the battery was disconnected and I desperately tried to pull on to the hard shoulder. I then had to get out of the car, lock it, unlock it and get back in - it then worked. Absolutely terrifying if I'd been in the outside lane. Now I feel I have lost my confidence in the car...is it something that can be resolved?

 

[Rolfe]

One would certainly hope so, but if might be difficult to replicate it so you can prove what's happening. I think you should report this to your dealer, making your displeasure very clear.

What driving mode were you in at the time? Did you have ACC or TJA engaged?

Welcome to the forum, by the way.

 

[SarahT]

Thanks @Rolfe what do ACC or TJA mean and how would I be able to find out if I had them engaged?!

 

[siteguru]

ACC = Adaptive Cruise Control ... you should know whether or not you had that engaged. (It's the middle button on the left side of the steering wheel, provided that the ACC - or TJA - option is selected in the Car settings menu in the Infotainment screen).

TJA = Traffic Jam Assist = ACC plus automated steering. A sort of "poor man's" auto-pilot.

 

[Rolfe]

Thanks @Rolfe what do ACC or TJA mean and how would I be able to find out if I had them engaged?!

Ah.

ACC is adaptive cruise control and TJA is traffic jam assist. The former is a nifty driver aid that keeps the car at the speed you select (like an ordinary cruise control) but if it's following a car going more slowly than that it will latch on to it and play follow-my-leader rather than simply smashing into the back of it. Brilliant for roads where the speed limit is lower than you might otherwise be driving, like 20-30 mph limits and motorways.

The latter does a similar thing but will also steer the car to follow the one in front as opposed to merely maintaining distance. It's meant for slow-moving traffic.

If you don't know what these are then you didn't have them on, but they're worth finding out about.

 

[SarahT]

Thank you @Rolfe I have checked and I didn't have them on, but I might experiment with them. Would it be the case that they'd help prevent the car from automatically cutting out if it detects a vehicle in front (like front collision assist)?

 

[Rolfe]

I was wondering if it was a malfunction in one of these that had caused your problem, but it seems not. Front collision assist is going to slam the brakes on if it thinks you're about to hit something. If the car is already matching its speed to the car in front that would be less likely to happen I suppose.

I find ACC very useful and it's worth experimenting with it, but I don't think it's related to this specific issue.

 

[NLMGSAN]

@Rusty168 exactly the same thing happened to me yesterday. Had the EV4 for 2 months, driving on a busy A road with my family in the car, I braked gently and suddenly the car power went, a message flashed up saying the battery was disconnected and I desperately tried to pull on to the hard shoulder. I then had to get out of the car, lock it, unlock it and get back in - it then worked. Absolutely terrifying if I'd been in the outside lane. Now I feel I have lost my confidence in the car...is it something that can be resolved?

Which battery? 12V?

 

[Rusty168]

Thanks all for your replies. It is helpful to know I am not the only one this has happened to.
Every time it has happened I have been in ACC and decelerating towards e.g. a roundabout or a junction.
The last time it happened I think it flashed up - HV Battery Shutdown. All the displays etc stay on but there is no power. No faults stay on. Just resets after coming to a complete stop.
The lease company and broker are passing book and saying I need to raise a complaint with mg. It’s been in once and my nearby mg garage is going to inspect again next week. I am encouraging them to speak to central MG for support. I will mention 12V connections when I get there next week.

Hi Sarah - what I have learned (in case it happens again) - you just need to put the vehicle in park with feet off the pedals. Then place foot on brake and it restarts and get the message “ready.”
If that doesn’t work you can shut down the car manually from the security screen.
If you swipe the normal display it shows e.g. vehicle and other settings. It’s in there sorry not in car so can’t guide exactly but think it’s under safety or security. Cheers Russell

@Rusty168 exactly the same thing happened to me yesterday. Had the EV4 for 2 months, driving on a busy A road with my family in the car, I braked gently and suddenly the car power went, a message flashed up saying the battery was disconnected and I desperately tried to pull on to the hard shoulder. I then had to get out of the car, lock it, unlock it and get back in - it then worked. Absolutely terrifying if I'd been in the outside lane. Now I feel I have lost my confidence in the car...is it something that can be resolved?

Which battery? 12V?

From a user point of view it’s the HV battery as there is no power. However, as a colleague pointed out, it may originate from the 12V having a micro disconnection.

 

[OriginalBigAl]

I'm no expert but it sounds like a faulty deacceleration sensor, when it happens do you feel the seatbelt tighten?

 

[Rusty168]

I don't believe so.
The first time it happened it was like the vehicle did an emergency stop and threw us towards the window. But might have been as was about 50mph. In full regen mode and sudden loss of power just meant decelerating. Thanks for reply

 

[DixieTGS]

From a user point of view it’s the HV battery as there is no power. However, as a colleague pointed out, it may originate from the 12v having a micro disconnection

A bit of a long shot, but that would be consistent with the MSD (Manual service disconnect) not being fully pushed home and latched or some other fault with the connector.

It is the yellow plug clipped to the 12V battery tray, but I would get the garage to check it as it will bring errors up on the drivers display and I don't know if there are any other consequences.

 

[Rusty168]

Thanks I will share that with garage next week

 

[Koomi]

Had a call from the other half a few weeks ago, she was sitting in a queue not going anywhere as the road ahead was closed for a cycle race, then all of a sudden the car shut down - not sure of error she told me on the phone at the time, possibly battery disconnected, possibly out of power - but had charged the evening before so should have been around 80%

Car is a good 7 months old at this point, never happened before, and never happened since.
Will bring it up when next passing the dealers, but sounds a lot like some others are experiencing.

 

[Rusty168]

Ok thanks. Well if the car restarted then unlikely battery charge but could be this fault. Adds to the case.

 

[Jto]

The fault - sudden loss of power and rapid deceleration as you desperately try and get to the hard shoulder. It might coincide with being in cruise and then braking.

Car needs to come to a full stop. Place in park. Foot on brake and car says ready and power is restored

I have had the car for three months. The car had this fault three times in the first two weeks. AA disconnected battery and fault seemed to stop. Happened a fourth time and took it into MG who updated the software. Just happened for a fifth time so it's not fixed.

Very dangerous. Has anyone else had this fault or had it resolved?

Hi
As the car has had this same fault 3 time I would start looking into having it replaced with a new car. The person work with used to be a BWW sale Manager for some years and this used to be the rule, now I do not know if covers all makes but look in to it.

 

[Derek clark]

The fault - sudden loss of power and rapid deceleration as you desperately try and get to the hard shoulder. It might coincide with being in cruise and then braking.

Car needs to come to a full stop. Place in park. Foot on brake and car says ready and power is restored

I have had the car for three months. The car had this fault three times in the first two weeks. AA disconnected battery and fault seemed to stop. Happened a fourth time and took it into MG who updated the software. Just happened for a fifth time so it's not fixed.

Very dangerous. Has anyone else had this fault or had it resolved?

Had similar faults on my zs ev. Rejected it and got money back. MGs are rubbish!