MG4 Standard Range 12v Battery Dead and Charging Problem

[bumleopard]

Hi all,

I want to share an ongoing issue with my MG4 standard range. The car is currently sitting in my driveway, dead as hell. I called the AA and they confirmed on visit the 12v battery is borked and is not taking any charge. The car will be towed to the garage either today or tomorrow.

So, how did I get here? 2 nights ago, I plugged the car in for an overnight charge (this was after a day's use). The next morning I see the car did not charge at all but it had enough juice to get me around for the day. That night I plugged it in again (it was at 13%). The next morning the car is completely dead. I opened it manually using the key but there was no power inside. The AA got it started with some jumper cables and I see the battery was still at 13%. This really feels like a dodgy software issue. No lights or anything were left on overnight but something drained the battery and possibly killed it. The MG's software regularly has trouble communicating with my Zappi v2 charger, making scheduled charging a lottery. Putting it bluntly, the software experience so far has been shit but this takes the cake. Hopefully a magic update at the garage, along with a new battery will fix these issues.

Anyway, I just want to share this in case others experienced something similar.

 

[Rolfe]

There is discussion of this in a number of other threads. There may be some sort of parasitic battery drain, or there may be a software issue where the car is neglecting to keep topping the 12v up from the HV battery. Or you may have a dud 12v battery.

It's slightly odd that some people are getting this but most people aren't. Maybe there has been a dud batch of 12v batteries from somewhere?

Best thing to do is to get a battery booster pack and keep it in the car. That way if it happens then you can get into the car with the manual key, open the bonnet, retrieve your booster pack, and get going. This should not be necessary on a new car, but better safe than sorry. It seems to be an issue with a lot of EVs, not just MG4s. I wonder if the requirements for the 12v battery in EVs haven't been properly thought through as yet.

 

[Anon70]

12v battery issues are not unique to MG, this was the cause that Hyundai found, some 3rd party app sending messages to the car 1,000s of time a day...

Hyundai Finds Causes For Ioniq 5's 12V Battery Drain, Reveals Fixes

Some Ioniq 5 vehicles were reportedly seeing as many as 5,000 Bluelink requests per day; Hyundai has now limited server traffic to 20 transactions per day.

insideevs.com

 

[JonEV]

Are all other software systems working as you expect?

I've seen a few cases of people reporting a DAB issue and dead battery on the same vehicle. The two seem linked somehow.

 

[tsedge]

Are all other software systems working as you expect?

I've seen a few cases of people reporting a DAB issue and dead battery on the same vehicle. The two seem linked somehow.

DAB = Drain All Battery...??!

 

[JonEV]

DAB = Drain All Battery...??!

Its all starting to make sense!!

 

[the briggie]

 DAB - Drained Again Bollocks.....?

I fitted a BM2 device across my 12v battery to monitor usage/drainage/charging. Using this I can see any 12v activities on a smartphone app. Useful...but should not be necessary...device

 

[GameZone]

Bought myself a branded 12v battery from Bosch. Haven't had any problems with the current battery, but im still replacing it.

 

[Kithmo]

I've had DAB problems but no 12v issues.

 

[Ian Key]

DAB - Dribbles After Beer?

Sorry, thought you were referring to me

 

[Lovemyev]

The one problem here is that the charging of the car needs sorting as a priority.
As it appears that the traction battery is not charging, then the 12 volt battery will not be receiving a charge either as a result of this surly ?.

 

[FlyingDutchman]

Had the same today. MG4 completely dead. AA tested battery and it showed just under 5v !

Booster brought car back and then it immediately started to try and charge the 12v battery. AA guy was amazed that the battery was showing 14.1v even though the car was not in ready mode. He didn’t expect it to be charging when this mode is not engaged. The only way we got it to go back down to normal levels was locking the car (ie no charging)

He also was amazed that the MG4 charged during wall plug in. In fact he did not believe it until I proved it.

But this still doesn’t answer the mystery that the car was topped up from 50 to 100% only three days ago. Which should’ve been plenty to charge to the 12v, let alone the driving it did to get it down to 50%!

Contacting MG in the morning and asking them to investigate / put a new battery in. FYI my Mg is a Nov 22 build car, Mar 23 reg.

 

[Tig170]

Must admit I was completely worried about this! - 3 weeks away on holiday in recent days (and yes couldn't contact the car after around 7 days, car in UK) - but no problems when got back - the HV battery was the same as one left it, 71%

EDIT : Car used daily - charged at home, 15000miles todate

 

[Dodgy]

Had the same today. MG4 completely dead. AA tested battery and it showed just under 5v !

Booster brought car back and then it immediately started to try and charge the 12v battery. AA guy was amazed that the battery was showing 14.1v even though the car was not in ready mode. He didn’t expect it to be charging when this mode is not engaged. The only way we got it to go back down to normal levels was locking the car (ie no charging)

He also was amazed that the MG4 charged during wall plug in. In fact he did not believe it until I proved it.

But this still doesn’t answer the mystery that the car was topped up from 50 to 100% only three days ago. Which should’ve been plenty to charge to the 12v, let alone the driving it did to get it down to 50%!

Contacting MG in the morning and asking them to investigate / put a new battery in. FYI my Mg is a Nov 22 build car, Mar 23 reg.

Had our MG4 a couple of months and have had ongoing issues with flat 12V battery. In Australia the car comes with MG Assist - a service comparable to the UKs AA. Had them out several times to get it started. My thinking was that we just happened to get a dud battery but it turned out to be otherwise. Got car back last week after an extended stay at the dealers and they reported the problem was a parasitic draw due to a faulty ‘Gateway Module’. The module was replaced under warranty and so far, all looks good.
The dealer tested the battery & advised it was OK. I know it went went down to abt 3V on three occasions so I’ve got some doubts remain abt the battery. We are away caravanning for extended periods when the MG4 will remain home unused and I’m contemplating fitting a negative battery pole isolating switch for those periods. If I have any more issues with the 12V battery itself I intend to replace it with an AGM battery.

 

[siteguru]

We also have MG Assist in the UK. As you say it is full AA (car only) cover, so includes roadside assistance, relay plus and home start.

 

[FlyingDutchman]

Had our MG4 a couple of months and have had ongoing issues with flat 12V battery. In Australia the car comes with MG Assist - a service comparable to the UKs AA. Had them out several times to get it started. My thinking was that we just happened to get a dud battery but it turned out to be otherwise. Got car back last week after an extended stay at the dealers and they reported the problem was a parasitic draw due to a faulty ‘Gateway Module’. The module was replaced under warranty and so far, all looks good.
The dealer tested the battery & advised it was OK. I know it went went down to abt 3V on three occasions so I’ve got some doubts remain abt the battery. We are away caravanning for extended periods when the MG4 will remain home unused and I’m contemplating fitting a negative battery pole isolating switch for those periods. If I have any more issues with the 12V battery itself I intend to replace it with an AGM battery.

That’s very interesting to hear, thank you for sharing. Somethings definitely wrong with it all, as I had my partner take a photo of the drivers screen where you can clearly see the battery not at charging voltage whilst driving. It seems really intermittent of when it puts on charge and I can only put that down to either a faulty gateway as you say or just poor software.

We also went away for 1 week to Greece and the car was fine.

Must admit I was completely worried about this! - 3 weeks away on holiday in recent days (and yes couldn't contact the car after around 7 days, car in UK) - but no problems when got back - the HV battery was the same as one left it, 71%

EDIT : Car used daily - charged at home, 15000miles todate

Yes the HV is ok, it’s the 12v I’m concerned about … glad to know yours was ok!