12V battery not charging

[Mr Gear]

Hi
I'm after some advice regarding my 12volt battery going flat on my drive home.
12V battery light came on, car worked OK so kept driving, when the battery got to 10V it dropped like a stone to 6V dash went off then car stopped working completely.

AA confirmed HV battery isn't charging the 12 volt battery, needs to be towed to garage.

My indra home charger has been acting odd lately, sometimes not finishing a charge, other morning red lights on charger, odd 1 tiny blue light on for a while but still charged, sometimes.

Could the charger of caused this fault? Could it be as simple as changing a fuse in my car?

MG garage said they can't look at it for 8 weeks!!!! so it's just sat in their lockup.

Hoping to fix it myself, or take a spare battery and swap them over every few days, at least I'll have a car.

The courtesy car has to be given back in 3 days, they won't extend it or sort another one until my car been looked at.

Garage tell me they have no loner cars to give me for 6 weeks

So come Tuesday I'm without a car.

Any advice appreciated, either about fixing the car or how to squeeze a loan car out of the main dealer

Thanks

 

[Jomarkh]

If you can get a 12V booster to allow you turn turn the car on into ready mode then see what the 12V is showing on the dash. While charging from the HV battery it should show around 14V.
What was the voltage showing and was it slowly dropping?

 

[MickeySw]

The car needs a 12V DC from the Aux battery to run, once ready, the HV battery will top it up via a DC/DC charger (around 14V as @Jomarkh mentioned)

If that no longer works, you can use an external 12V car battery charger to top it up manually overnight.

It could also be a faulty 12V battery itself causing issues.

As regards to fuses check the ones for the Combined Charge Unit, see location below.

Fuse Box Diagram MG MG5 EV (2020-2024)

Fuse box diagrams (location and assignment of electrical fuses and relays) MG MG5 EV / Roewe Ei5 (2020, 2021, 2022, 2023, 2024).

fuse-box.info

 

[johnnyg]

My heart goes out to you Mr Gear, 8 weeks is totally unacceptable for a broken down car to be looked at and to be left stranded.If it needs parts you could have to wait several more weeks for them.
MG really need to get their act together. The more I read of customer service issues like this on this forum, the less likely MG will get my business in the future. I’m not sure MG realise how competitive the new EV market is getting and how much customer service plays in making the choice of brand. Especially if you’ve had bad service from your current brand.

 

[Mr Gear]

The AA put his jump pack on and everything was fine,
The hv battery isn't charging it,
Driving home on 11V expecting to see voltage go up but it didn't,
When it got to 10V it dropped massively to 6V,
Dash went blank then car stopped.
But I'm hoping my wall charger being weird has blown a fuse, simple fix.

Thanks for the diagram, I'll probably pop over to the garage at weekend n check the fuses myself.

Although mg on phone told me not to change battery or even check fuses due to there being a hv battery.

But I will be checking them.

To be fair the initial assistance from mg was really good.
Had AA out, car towed away and driving home in a rental car all within an hour and a half.

But they only give you the car for 4 days, and it's down to the garage iv taken it to to provide a car which they said they don't have any for 6 weeks.

MG said they will provide a car once the car has been checked and it's been deemed a warranty job.

But they ain't going to look at it for 8 weeks So that's the problem. I guess mg didn't expect all the garages to be full with a massive back log of broken MG's

I wonder what the wait time would be if I was trying to book a service, bet its not 8 weeks

I have a spare 12V battery from another car, tempted to switch them over every couple of days, but MG don't recommend changing the 12V yourself.....idiots

 

[Alb]

Do you have any other MG dealers nearby?

 

[DavecUK]

I wonder what the wait time would be if I was trying to book a service, bet its not 8 weeks

At my nominated dealership under my service plan (Richmond MG, Moore Rd, Slyfield, Guildford, Surrey) , the wait time is 9 weeks for a 1st service on my MG4 and a little over 3 months for a diagnostic.

So consider your dealer good in terms of my local dealership. I have another local dealership in Epsom (Wilsons), same sort of wait times.

Palmers Hemel Hempstead, although they don't have loan cars for 6 weeks did my 1st service (a while you wait) 2 weeks after I booked. When the "not charging" problem still existed, booked it in for the diagnostic 5 days later (happening today). I don't know how long a fix will take though, as it probably needs a new CCU. The only problem is they are a 72 mile round trip from me and no good public transport links, but I would rather use them if I can, and would be more inclined to if the loan car situation was better.

I think we need a law change to protect consumers, as lack of loan cars and overly long waits seem to apply to a number of brands, not just MG e.g. don't ever, ever, buy a BMW electric vehicle, I had 2 and never again! They're good, but dealer backup isn't what it should/used to be.

The UK government should make it law, that under warranty, main dealers are required to do things in n weeks, loan cars should be available when a vehicle is under warranty and if the dealership doesn't have any, hire cars should be provided. I think if this became law, it would drive significant change to the benefit of consumers. At the moment you have more rights buying a bag of fruit, or a TV.

 

[MickeySw]

But I'm hoping my wall charger being weird has blown a fuse, simple fix.

I’m inclined to think it’s the other way around, because your 12V aux was low, the wall charger was acting up? No harm in checking the fuses but if they are OK, most likely the CCU has gone faulty.

If I were you I’d charge up your spare battery fully overnight and swap it the next day, the dash might light up like a Christmas tree afterwards but usually driving a few yards will sort that.

Hopefully the suspected CCU fault doesn’t add an extra load to the battery so keep a close eye on the voltage.

If the original battery is gone down to 6V it’s most likely faulty (and certainly will be in 8 weeks time if left in the car). Battery warranty is only 1 year so you may have to invest in a new one anyway.

Fully charge even a new one overnight and swap it once the other one gets below 12V. That should keep you going until your appointment.

 

[Mr Gear]

Do you have any other MG dealers nearby?

Quite a few, iv rung round 4 so far all telling me the same thing, I was getting sick of the bs they feed you, ill end up screwing at them, couldn't handle any more rejection lol

I was planning on doing the battery swap every other day idea, don't need to now, I forgot my dad has 2 cars, he is going to lend me his mini cooper convertible.
Borrowed it last time when I was waiting months for delivery of the MG
Always considered them girls cars but ended up quite enjoying it.
But I'm not telling MG I've got a car to use, they shouldn't get away with it, I'll still complain to them daily, and the garage.

Also my charger was being weird before the car went wrong.
Few weeks ago it only partially charged my car, and had only 1 tiny blue light on charger, boost button stopped doing anything not even a beep when pressed, nothing about it in manual, but it continued to charge my car. A couple of times it only did a part charge again, then one day I came home and the wall charger was flashing red, turned it off n on, it went back to the tiny blue light again but this time it wouldn't charge at all,
I'd plug it in, car would detect it had been plugged in, could hear charger click, and hear lock in plug lock, like it was about to charge, but nothing would happen, car said, connected but not charging.
I left it plugged in anyway, overnight, hoping it would sort itself out, in morning car hadn't charged but my 12V was down to 11V with red battery symbol on dash.
So this is why I thought maybe the charger has done this to my car

 

[Alb]

It's unbelievable that breakdowns aren't made a priority for any dealer. Fixing the problem may take a while but confirming that there is a problem covered by warranty in the first place probably takes very little time.

 

[RichP]

I wish you the very best of luck. It took the dealer 6 months (I was carless over the whole period) to resolve my issue with no courtesy car except for 3 days when I pleaded with them. And MG UK don’t want to know either. Unfortunately will never buy another one

 

[Mr Gear]

Update
Mg garage rang last week, say I need new 12V charger unit, should be ready this week.

They rang back on Monday said they fixed the 12V problem but 2 more faults have appeared, to do with the charging system for the HV battery and are waiting to hear back from MG.

At least they have looked at it sooner than the 8 weeks they originally said it would take.

Still think it was my home charger that caused this.

My home charger currently has a solid orange light which apparently is to do with a voltage problem and Indra will tap in remotely to see what's going on and will be in touch, that was Monday, not heard any yet.

 

[Coulomb]

Still think it was my home charger that caused this.

I don't think so. The DC-DC is a separate power converter to the on-board charger, even though in many vehicles they are combined into the same box. The reason for combining them is just that both need connection to the High Voltage battery, so it's convenient to use the same HV cables.

We know that SAIC are having problems with the CCU, which I think is the combined on-board charger and DC-DC. Something to do with the chip shortage.

Since the 12V battery voltage isn't increasing, the DC-DC is not working. It does have a fuse, but it's probably something like a 150A fuse bolted inside the DC-DC box. Not user replaceable, at least without a lot of work.

Lead acid batteries don't last long when deeply discharged for more than a day or two. So the 12V battery will be toast, and this can cause all manner of problems in any car that is full of computers. It could well have caused your EVSE (home "charger") to act strangely, as the handshakes between the EVSE and the car will probably have been affected by the very low and unpredictable 12V in the car.

I hope that the dealer has replaced the 12V battery and charged it properly before installing it. Otherwise, that could be the cause of the final two fault codes. This is something that EV repairers find out early on, but it seems that some dealers, who work with ICE cars way more than with EVs, take a long time to learn these lessons.

 

[Mr Gear]

MG garage said they borrowed something off another car they thought was the problem, but it wasn't.
They do seem to just ring MG and ask what to do next, like they don't know how or what to fault find on an electric car.
My home charger had its normal lights on after I reset it a couple of weeks ago,
Haven't used it since, but its still decided to show voltage error now, even tho it hasn't been touched.
So I have a car they can't fix and a broken charger.
Deffo going back to ICE when lease fiishes next year...God I miss my Amarok

 

[dragon2611]

My home charger currently has a solid orange light which apparently is to do with a voltage problem and Indra will tap in remotely to see what's going on and will be in touch, that was Monday, not heard any yet.

I'd see if you can get any data from them relating to that, as if your incoming grid voltage is out of spec you need to get onto the DNO for your area and get them to fix it.

 

[emmrecs]

I'd see if you can get any data from them relating to that, as if your incoming grid voltage is out of spec you need to get onto the DNO for your area and get them to fix it.

Agree 100%!

In the early days of my home charger installation, even before I actually had the car, I received messages in its app that it was repeatedly "off-line" and needed to be rebooted.

Long story short: eventually, after much testing and trial and error, my installer discovered that the voltage supplied to my house was sometimes exceeding the legally mandated range, which is 216 to 253 volts. Occasionally it was as high as 259. This caused the charger fault protection to activate and turn the charger "off". Once my DNO had confirmed the problem they adjusted the incoming voltage at the local substation and it has been absolutely fine since then.

 

[dragon2611]

Voltage out of spec could be something as simple as some adjustments being needed, or it could be indicative of a bigger problem developing, either way if you have evidence of it occurring the DNO should take an interest.