MG4 77 kWh Extended Range max charging rate

[slith]

I have had an MG4 77 kWh for a few weeks now. I am charging it for the first time to go on a long trip. The specifications say the charger should charge at 11 kW, 3-phase. My Evnex X22 (3-phase) charger says the charging rate is 10.4 kW. The car says it is charging at 9.6 kW. I cannot see the current the charger is putting out, but when I called Evnex they said it was drawing between 14 and 14.2 A @ 245V per phases, which comes very close to the 10.4 kW figure it indicates. Are other people experiencing this issue where it is not drawing the full 16 A per phase? I can accept that there are losses from AC-DC conversion so with 10.4 kW charging, I get that 9.6 kW is realistic. However, it should still be drawing more current.

When I set the AC charge current to 16A, it then seems to limit it to a maximum of 16A across the 3-phases (ie, 5.3A per phase around 3.0 kW) instead of 16 A per phase. Same sort of thing happens with setting the AC charge current limit to 8A or 6A. Is this the way it is meant to work.

 

[kenneth104]

This is a normal situation. When we talk about power, we are talking about it from the perspective of the charging pile. The car actually needs to convert, and the power obtained will be lower.
Usually 11kw is actually 16a x 220v x 3phases

 

[wattmatters]

When I set the AC charge current to 16A

In the car? That should be set to "max".

I am charging it for the first time to go on a long trip. The specifications say the charger should charge at 11 kW, 3-phase. My Evnex X22 (3-phase) charger says the charging rate is 10.4 kW. The car says it is charging at 9.6 kW.

The EVSE will adapt to the supply and may adjust its max charge current a little.

As to the power losses between the supply circuit and the drive battery, that's normal.

The car is reporting the DC charge rate into the drive battery. The onboard AC to DC converter has losses plus the car is using some energy for other systems, including charging of the auxiliary 12 V battery (can consume 100-300 W).

 

[Coulomb]

Are other people experiencing this issue where it is not drawing the full 16 A per phase?

Yes, it's not really an 11kW on-board charger, I've heard that it's closer to 10.5kW.

Similarly, the single phase charger is more like 6.6kW than 7.2kW, at least on some models.

When I was charging a Nissan Leaf ang MG ZS EV Mk 1 from the same EVSE, I noticed that the MG drew less current than the Leaf at the same setting. It's faintly irritating.

When I set the AC charge current to 16A, it then seems to limit it to a maximum of 16A across the 3-phases (ie, 5.3A per phase around 3.0 kW) instead of 16 A per phase.

Is this setting the limit in the car or at the EVSE?

My understanding is that this is not the standard behaviour; three phase current is always reported as per-phase. I assume that the Type 2 standard (IEC 62196-2) specifies what the behaviour should be at the EVSE. I suppose that the car is free to behave however it wants, but it would make much more sense to me if the current limit was per phase.

It's not as if there is ever a single conductor that carries all the current. The neutral carries almost no current if the phases are reasonably balanced. Even if one phase drops out, the neutral carries a similar current to that of the two active phases. The current limits are ultimately about the limits of individual conductors.

 

[Jamesrr]

I get 10.6kW reported by the car, ismart and from the Tesla wall charger app itself.
Works for me!

 

[slith]

I'm not concerned with the discrepancy between the 10.4 kW the charger claims and the 9.6 kW the car is indicating. I understand there are AC to DC losses.

My concern is that the car is not accepting the full 16 A, 230 V for 11 kW which it indicates in the specifications. The charger tells the car it can provide 16 A, but the car is only asking for just over 14 A. Why isn't it taking the full 16 A on offer? The battery was only 50% full so I don't see any reason to limit the charge rate. If it can fast charge on DC at over 10x this rate it should be able to accept the full 11 kW.

My understanding of the charging process is that the EVSE indicates the maximum current it can supply and the car then takes what it wants. So, the charger offers 16A and the car only takes 14A. The exact voltage at the time will determine the kW it is consuming. In Australia, nominal voltage is 230V, but it varies based on load and generation, time of day. The actual voltage is -6% to +10% (216 to 253 V) so the 245V at the time is not unusual.

Yes, it's not really an 11kW on-board charger, I've heard that it's closer to 10.5kW.

Both the manual and the specifications indicate that max charging rate is 11 kW.

Similarly, the single phase charger is more like 6.6kW than 7.2kW, at least on some models.

When I was charging a Nissan Leaf ang MG ZS EV Mk 1 from the same EVSE, I noticed that the MG drew less current than the Leaf at the same setting. It's faintly irritating.

It is irritating. I have seen on the smaller capacity models that it indicates the AC charging rate is 6.6 kW max. I can see that they aren't drawing the full 32 A here. My wife has an CX-60 PHEX and it charges at 7.2kW - 7.4 kW every time.

Is this setting the limit in the car or at the EVSE?

I don't have any setting on the EVSE to set the current. It always offers as much as it can. There is a setting on the MG4 called "AC Current" - there are 4 options: 6 A, 8 A, 16 A and "AC Current". The AC Current option doesn't make sense. I feel like the button should be called AC Current, but the options should be 6 A, 8 A, 16 A and "Auto" or "Max", but even then 16A is the max on 3 phases. Maybe it can accept 32A or close to it on single phase only charging. It's weird. There is nothing in the manual regarding the Energy Management settings. However,

My understanding is that this is not the standard behaviour; three phase current is always reported as per-phase. I assume that the Type 2 standard (IEC 62196-2) specifies what the behaviour should be at the EVSE. I suppose that the car is free to behave however it wants, but it would make much more sense to me if the current limit was per phase.

It's not as if there is ever a single conductor that carries all the current. The neutral carries almost no current if the phases are reasonably balanced. Even if one phase drops out, the neutral carries a similar current to that of the two active phases. The current limits are ultimately about the limits of individual conductors.

Yes, it seems bizarre that when I select 16 A it drops to 5.33 A per phase. I confirmed that is what happened when I had the EV charger technical support on the phone.

In the car? That should be set to "max".

There is no option for Max. There are 4 options - 6 A, 8 A, 16 A and "AC Current". That last one seems like a bug, but perhaps should be called Max. I had it set to "AC Current" when it was charging at 9.6 kW. I just tested the other options to see what would happen and it then reduced the current to 2 A per phase, 2.66 A per phase and 5.33 A per phase for the 6, 8 and 16 A options. When I put it back to AC Current it ramped up to 14A per phase/9.6 kW.

The above photo shows the options the car is offering for AC current. I disabled the charging when the sun went down and will resume tomorrow.

The EVSE will adapt to the supply and may adjust its max charge current a little.

My EVSE has solar capability. Solar was exporting over 20 kW at the time. I told the EVSE to "Charge Now" which means it offers as much as it can. It is entirely possible there is a fault with my charger as I have not tested my EVSE 3-phase charging on any other vehicle and I have not tested my MG4 on any other charger. When I spoke to my EVSE technical support, they said that it was offering 16 A per phase, but the car was only taking 14-14.2 A.

As to the power losses between the supply circuit and the drive battery, that's normal.

The car is reporting the DC charge rate into the drive battery. The onboard AC to DC converter has losses plus the car is using some energy for other systems, including charging of the auxiliary 12 V battery (can consume 100-300 W).

I understand there are losses of around 7-8%. I'm not sure though what that 9.6 kW figure actually means. It could simply be calculating 14A x 230 V (nominal) x 3 phases = 9.6 kW, or that could be the DC charging rate after AC-DC losses. I can't be sure what it means exactly since the manual does not say. I suspect it is the former.

 

[siteguru]

Assuming that the ER onboard charger is the same as/similar to the early Trophy LR cars in the UK (and maybe also still in EU), it is rated to 11kW 3-phase but anecdotal evidence is that actual charge rate into the battery is about 10kW or a little less. However when connected to a single phase source (power arriving only via the L1 pin) then the charger internally switches to use 2 of the onboard phase charger units ... this gives more like 7kW charge rate from a 32A supply rather than the 6.6kW that the single phase onboard chargers support in the UK SE model and later Trophy models.

 

[wattmatters]

There is no option for Max. There are 4 options - 6 A, 8 A, 16 A and "AC Current". That last one seems like a bug, but perhaps should be called Max.

Yes, it's the same as selecting max. Not sure why it has that name and I agree it's a silly. I must have just reprogrammed myself to refer to it as "Max".

That would probably be because:
i. that's what the function does so my brain reassigned it!
ii. in my SAIC Home Assistant integration the charge current limit options are 6A, 8A, 16A and Max:

The specifications (Australia) just for interest (I know you know this, just handy for everyone's reference):

There's nowhere in the user manual or spec sheet stipulating an actual maximum current draw. It only refers to the onboard charger power rating (6.6 kW single phase / 11 kW 3-phase).

In the charging times charts it refers to "approx 11 kW" for the 3-phase options:

Here's a brief video showing the data from a charge session the other day, nearly 1.5 hours at max charge rate setting, until the car ended the session as the 80% charge limit had been reached and so went into balance mode for a handful of minutes.

MG4 Essence 64
EVSE: ZJBeny single phase 32 A OCPP model.



Can see AC current draw is rock steady 30.5-30.6 A.

The power demand however varies between 6.68 kW and 7.18 kW with the variance during the session due to changes in line voltage.

We get significant voltage variance being at the end of a rural power line. Note the line voltage jump up by more than 20 V when the main charging session ceased.

While I do not display it, the power factor remained steady at 0.999 throughout the main charge session.

I don't have the same granularity of data on the DC power (the HA integration only takes a data sample every so often) but the data I do have shows the DC power delivery varied between 5.89 kW and 6.29 kW.

I've no idea whether the 77 onboard charger is really capable of drawing the full 11 kW. Certainly my single phase 64 is capable of a power draw resulting in more than a 6.6 kW draw on the supply circuit.

 

[dsimpkins]

The car says it is charging at 9.6 kW

Sounds correct to me. I use a 22kW charger at work with a 3 phase charging lead, and this is what my car says it is charging at. Also draws about 14.5A per phase on the charger (according to the display on the charger)