Car dead after 2 weeks, won't open

[AdamMGEV]

Owned my MG4 for about a year now. Been on holiday for 3.5 weeks and after 2 weeks it stopped responding to the app. I know it had plenty of battery so what's happened? Won't even unlock. Does that mean the 12v battery is dead? If so that's not very good is it. Thank god I didn't take it to the airport.

 

[MuzGB1970]

I'm guessing it was the 12V battery. It is mentioned in the manual that you need to "turn on" the car to charge the 12V battery regularly, I don't remember the timescale but seem to think it was about 2 weeks. Checking via the app will discharge a small part of 12V battery each time, which won't help, also you may have had plenty of charge in the HV battery but this doesn't top up the 12V battery unless the car is "switched on".

 

[fnegroni]

Owned my MG4 for about a year now. Been on holiday for 3.5 weeks and after 2 weeks it stopped responding to the app. I know it had plenty of battery so what's happened? Won't even unlock. Does that mean the 12v battery is dead? If so that's not very good is it. Thank god I didn't take it to the airport.

It won’t unlock: is the battery in the remote dead?
Plenty of charge left in the car: at what percentage ?

The car will top up the 12v battery but it’s not certain when and how long for. And as @MuzGB1970 stated, even the manual does say to have the car on and in READY mode for at least half an hour every week. Basically if you don’t drive it much. This isn’t so critical when the 12v battery is in a good state of health and charge.

If your 12v battery wasn’t in a good state of health I’m afraid these things happen.
12v batteries must be kept at 100% as much as possible. But if they’ve never been charged to 100% properly then they will struggle to keep the charge.

Luckily you can now buy LFP 12v batteries. Whether those are compatible with the MG4 I don’t know.

 

[AdamMGEV]

Tried both keys and neither work, manually unlocked the door and tried lights etc in car and nothing responds.

50% charge when I checked via app a week or so ago.

Ive called AA and they are coming out, said the battery will be dead. Would not be good if I had it at the airport and doesn't fill me with confidence for next time if we do want to leave it anywhere.

So what advantage does the new LFP battery give you?

 

[ianwlk]

Absolutely ridiculous that M.G allow this to happen in a motor car designed in the 21st century

 

[AdamMGEV]

Absolutely ridiculous that M.G allow this to happen in a motor car designed in the 21st century

Completely agree. I should be allowed to leave my car whilst on holiday and it starts when I get back. Any battery should last longer than a few weeks if not being used.

Oh and another thing my Skoda Enyaq is fine

 

[tsedge]

So I went on holiday for 3.5 weeks and after 2 weeks it stopped showing me on the app the status. I know it had battery left but got home and now won't respond so will have to try and manually open the door and try to get it revived. Any suggestions? Why would it do this? Thank god I didnt take it to the airport.

The car is supposed to go into a deep sleep within 48 hours when you leave it. In this state the app will not work. It isn't a good idea to keep checking on it with the app when leaving it as this will stop it going into the deep sleep state - and thus promote battery drain.

It should keep the 12V battery topped up of you have more than 50% SOC, but if you leave it with less than that then the deep sleep is essential to stop the 12V from being discharged.

MG recommend if leaving the car for a month or longer disconnecting the 12V battery to preserve it.

If this has happened to your car then it should come to life immediately when you connect another 12V battery to 'jump' it into life.

General recommendation for an airport trip is:

• Leave the car with between 60-80% SOC.
• Do not use the app to check on the car while it is away.

 

[MG4NI]

This year I have been away on holidays for 4 weeks, 3 weeks and recently nearly 5 weeks. I have parked my car (Trophy) in the driveway and not once looked at the App whilst away. Each time it has started without issue on my return. So this is not a problem on all MG4's. Hope you get to the source of the problem.

 

[tsedge]

It is a weakness of modern EVs in general (the 12V system) and many makes have experienced similar problems, including Tesla. It really needs redesigning into a redundant modular system so if the 12V system runs low you can still open and drive the car.

Best advice seems to be:

• Keep SOC between 60-80% when you leave the car for long periods.
• Let it go to sleep properly (don't wake it with the app while you are away).
• Consider carrying a 12V booster in the passenger compartment.

There are some bugs that cause a drain, may be solved with updates, otherwise it is quite common to replace 12V batteries every 2 years with EVs as they seem to be poorly made and take a beating.

 

[siteguru]

Given that they've "tried both keys" then that assumes they're physically at the car.

 

[Kithmo]

Given that they've "tried both keys" then that assumes they're physically at the car.

Yes just spotted that they got back and tried it on the duplicated other post.

 

[Rolfe]

As others have said, it seems likely that your repeated checking of the car with the app has prevented it from going to sleep, and as a result the 12v battery is flat. This is fixable in about a minute and a half with a jump start kit, or even a jump start from a nearby ICE car if you have jump leads. It's nothing to do with your LFP battery, that will be fine.

When I left my car in an airport car park I took a lead-acid jump start kit with me just in case but I didn't need it. I didn't touch the app all the time I was away - just over two weeks. This was the reason I left it in the airport car park - I knew it would be safe there so I wouldn't be tempted to use the app to check.

I'm thinking of buying one of these to carry all the time, just in case. The lead-acid thing is too bulky and heavy to do that.

Amazon product ASIN B016UG6PWE
Another point, there seems to be a level of HV SoC at which the 12v battery won't be topped up while the car is parked. Some have suggested it's as high as 50%, which seems mad. But it's always wise to leave the car with plenty charge when you're away for a bit. Sounds as if the problem here was the repeated checking with the app though.

 

[AdamMGEV]

I probably checked the app three times whilst away, so three times in 2 weeks, I wouldnt call that excessive, I wanted to check my car was ok, and there was definitely more than 48hrs between checking. The AA guy has been and got it going again. He said the battery was completely flat. He took it for a drive and then told me to leave it in ready mode for an hour for it to charge the battery. He said its a very common thing with modern cars now, he said there's a guy at Manchester airport that all he does all day is go around starting peoples flat batteries, EV or non EV.

I know for next time if over 2 weeks to disconnect the battery however at 10pm with family after a 14 hour flight I really don't want to be messing with the car and battery.

 

[Artful]

There could be an easy fix for this an inline cut off switch. Maybe this should be fitted as standard now to all new vehicles.

 

[SimonS]

I've got the NOCO GB20. I don't know that i'd want to try starting an ICE with it but it's fine for kicking the MG4 into life. Less than half that price too.

 

[Rayz]

I'm guessing it was the 12V battery. It is mentioned in the manual that you need to "turn on" the car to charge the 12V battery regularly, I don't remember the timescale but seem to think it was about 2 weeks. Checking via the app will discharge a small part of 12V battery each time, which won't help, also you may have had plenty of charge in the HV battery but this doesn't top up the 12V battery unless the car is "switched on".

Yes I agree it needs to be in the ready position.which you need to press brake and press start this definitely charges your battery I have checked it through the BM 2 monitor.But remember it's a 400- 14 v, so based on Voltage and not so effective as an alternator.

 

[Rolfe]

I probably checked the app three times whilst away, so three times in 2 weeks, I wouldnt call that excessive, I wanted to check my car was ok, and there was definitely more than 48hrs between checking. The AA guy has been and got it going again. He said the battery was completely flat. He took it for a drive and then told me to leave it in ready mode for an hour for it to charge the battery. He said its a very common thing with modern cars now, he said there's a guy at Manchester airport that all he does all day is go around starting peoples flat batteries, EV or non EV.

I know for next time if over 2 weeks to disconnect the battery however at 10pm with family after a 14 hour flight I really don't want to be messing with the car and battery.

I would agree, three times in two weeks doesn't seem excessive. In other threads about this issue, some people's batteries have gone flat after only a short absence, while others have been fine for weeks. Mine was OK for just over two weeks and I think someone else said they were OK after six.

Points that have arisen, other than don't keep waking your car up to see if he's missing you, are make sure the traction battery is above 50% when you park up, and make sure the terminals on the 12v are tightly secured. Some people have had the problem because of loose battery connections.

My plane got in at 3 am and the car was in an open-air car park with little light and cars jam-packed against it front and sides, so you can imagine how glad I was that he woke up on demand. I did have that lead-acid jump starter kit in the rear footwell, but God knows how I was going to get the bonnet open and the terminals on in these conditions.

 

[Rolfe]

Absolutely ridiculous that M.G allow this to happen in a motor car designed in the 21st century

It happens all the bloody time though, and not just to MGs.

 

[Rolfe]

I've got the NOCO GB20. I don't know that i'd want to try starting an ICE with it but it's fine for kicking the MG4 into life. Less than half that price too.

My concern about the cheaper one was that people were saying that if you forgot to charge it and it completely discharged, it would brick and you'd never charge it again. The expensive one is reported to be more robust in that respect.

 

[tsedge]

I probably checked the app three times whilst away, so three times in 2 weeks, I wouldnt call that excessive, I wanted to check my car was ok, and there was definitely more than 48hrs between checking. The AA guy has been and got it going again. He said the battery was completely flat. He took it for a drive and then told me to leave it in ready mode for an hour for it to charge the battery. He said its a very common thing with modern cars now, he said there's a guy at Manchester airport that all he does all day is go around starting peoples flat batteries, EV or non EV.

That suggests them that your car wasn't going to sleep as it should have been, which may have been why the 12V battery drained. Either there's a bug/fault or perhaps you had something left plugged in somewhere that was causing a drain.

Yes, modern 12V batteries are often rubbish - they are built to be as cheap as possible, not to last.

I know for next time if over 2 weeks to disconnect the battery however at 10pm with family after a 14 hour flight I really don't want to be messing with the car and battery.

This definitely sounds abnormal. You should have found the app didn't work after a couple of days as the car went to sleep, but clearly that never happened.