MG4, fault with rapid charging

[ippy1]

Good luck, and take heed of @siteguru's advice.

I will, thanks for your help.

 

[tsedge]

Best of luck @ippy1, these charging problems seem rare but have been coming up for more people lately.

With pure AC charging issues it tends to be a CCU (Charge Control Unit) issue which is fixed by replacing it. Sometimes it seems this can affect/fix DC issues too. However, as DC charging is typically direct to the battery, this could be an issue within the battery which is hard to fix, which might explain the delay. Battery replacement has happened to a few people but it is a last resort due to the huge cost to MG.

Anyway too much speculation on the cause isn't helpful but I wish you well with getting this resolved. Keep up the pressure, get in touch with your dealer and MG as regularly as you can to make yourself a "squeaky wheel" they can't ignore and hopefully they'll get there in the end.

 

[ippy1]

Best of luck @ippy1, these charging problems seem rare but have been coming up for more people lately.

With pure AC charging issues it tends to be a CCU (Charge Control Unit) issue which is fixed by replacing it. Sometimes it seems this can affect/fix DC issues too. However, as DC charging is typically direct to the battery, this could be an issue within the battery which is hard to fix, which might explain the delay. Battery replacement has happened to a few people but it is a last resort due to the huge cost to MG.

Anyway too much speculation on the cause isn't helpful but I wish you well with getting this resolved. Keep up the pressure, get in touch with your dealer and MG as regularly as you can to make yourself a "squeaky wheel" they can't ignore and hopefully they'll get there in the end.

Well, the engineer who I saw suggested he thought it needed the CCU replacing, but it’s up to MG to decide. Sometimes they ask the engineer for advice and sometimes they take control. But that was almost a month ago now. It’s the appalling reaction times and lack of any feedback that’s the big problem.

 

[tsedge]

Well, the engineer who I saw suggested he thought it needed the CCU replacing, but it’s up to MG to decide. Sometimes they ask the engineer for advice and sometimes they take control. But that was almost a month ago now. It’s the appalling reaction times and lack of any feedback that’s the big problem.

Yes, I understand and I agree. Sadly that is how MG is for the moment. But by pestering them some people have got breakthroughs.

 

[Wudus]

A bit of info in case it’s useful for anyone having trouble with DC charging. I had a fault on my MG4 SE LR (reg Apr 2023) where it would charge on AC but not DC. I don't know why the fault appeared. I had to make a couple of unsuccessful visits to two different dealers but the fault was eventually fixed by software updating of these modules: EVCC, BMS, CCU, IMCU, EPMCU.

 

[ippy1]

A bit of info in case it’s useful for anyone having trouble with DC charging. I had a fault on my MG4 SE LR (reg Apr 2023) where it would charge on AC but not DC. I don't know why the fault appeared. I had to make a couple of unsuccessful visits to two different dealers but the fault was eventually fixed by software updating of these modules: EVCC, BMS, CCU, IMCU, EPMCU.

I’ve had this fault for almost a year now! Lost count of how many times it’s been in to try and fix. It’s in again on Monday to replace CCU and some other part, since I made official complaint, and only contacting dealership via MG now.
Dealership were authorised to order the parts and repair over a month ago, but failed to contact me. Hence the complaint.

I’ve had this fault for almost a year now! Lost count of how many times it’s been in to try and fix. It’s in again on Monday to replace CCU and some other part, since I made official complaint, and only contacting dealership via MG now.
Dealership were authorised to order the parts and repair over a month ago, but failed to contact me. Hence the complaint.

Does anyone know what these modules actually are? I’ve heard CCU mentioned before elsewhere.

 

[Ian Key]

CCU - combined charging unit
BMS - battery management system

Not sure on EVCC, IMCU, EPMCU

 

[siteguru]

EVCC = Electric Vehicle Charge Controller (I think).

Can't remember re. the other two.

 

[TerryN]

I think:
EVCC = Electric Vehicle Communication Controller
IMCU = Intelligent Motor Control Unit
EPMCU = Electric Parking Motor Control Unit

 

[DelBoy]

For what it's worth I have had the CCU replaced and it took quite some time due to a lot of CCU's being replaced on the Gen 1 MG 4. After several visits MG replaced it and now it is working fine. Unfortunately Howard MG Weston-super-mare has since stopped being MG (who were really good) and now I have to re-engage with an MG garage in Bristol, very poor on MG's part

 

[tsedge]

CCU = Combined Charging Unit. This contains both the AC to DC converter (used for AC charging) and the DC to DC converter used for DC charging.

BMS = Battery Management System. This is the electronics that manages the HV battery and balances it and protects it.

EVCC = Electric Vehicle Communication Controller. This is the bit that talks to the external charger, speaking CCS or Type 2 as needed.

IMCU = Intelligent Motor Control Unit. This manages the electric motor and (presumably) handles regen.

EPMCU = As above, manages the electronic parking brake.

Note that the CCU can suffer partial failure, such as AC to DC, which I experienced with DC charging still working fine.

As ever, if it is a software problem then updates can help. If it is a hardware problem, new parts are needed and then software updates will also get applied to match the new parts.

Dealers will invariably try software updates first as it is a darn sight cheaper than fitting new parts and avoids parts delays.

 

[Coulomb]

CCU = Combined Charging Unit. This contains both the AC to DC converter (used for AC charging) and the DC to DC converter used for DC charging.

The DC-DC is a ~2.5kW unit for charging the auxiliary (nominally 12V) battery. The up to ~125kW of rapid DC charging of the main battery is supplied externally, usually by back room electronics, or for smaller rapid chargers, in the consumer facing dispenser itself. The back room rapid charger is often a honking DC-DC converter, operating from a ~900VDC bus, supplied by a honking AC to DC rectifier.

That's the main reason that when the on-board charger (the AC to DC converter) fails, you can still rapid charge. For rapid charging, you only need a pair of contactors and the EVCC module, with help from the BMS module. Even the DC-DC converter can fail, as long (as you charge the 12V battery at home) and you could still rapid charge.

 

[tsedge]

The DC-DC is a ~2.5kW unit for charging the auxiliary (nominally 12V) battery. The up to ~125kW of rapid DC charging of the main battery is supplied externally, usually by back room electronics, or for smaller rapid chargers, in the consumer facing dispenser itself. The back room rapid charger is often a honking DC-DC converter, operating from a ~900VDC bus, supplied by a honking AC to DC rectifier.

That's the main reason that when the on-board charger (the AC to DC converter) fails, you can still rapid charge. For rapid charging, you only need a pair of contactors and the EVCC module, with help from the BMS module. Even the DC-DC converter can fail, as long (as you charge the 12V battery at home) and you could still rapid charge.

Thanks, that all makes sense. The CCU must have some involvement in DC charging though because some people have had their DC charging issue fixed by CCU replacement - or at least that is what they've been told by their dealer.