22kw charger speed

[MundaneMatt]

Hi everyone, I used a Genie Point with my ZS EV for half an hour whilst I went shopping, and achieved a faster than expected charging rate.

The DC 50kw CCS Combo was bust, so I used the Type 2 cable in the 22kw port and just expected the usual max 7kw charging speed.

But I came back to having received 4.69kw in 31 minutes. That's faster than 7kw, but I didn't think the ZS EV could charge at faster than this as it's single phase AC only?

Has anyone else experienced weirdly fast AC charges?

 

[JodyS21]

Very strange, the onboard "charger" definitely doesn't handle 3 phase AC & is only rated at about 7kW.
Quick calc, so 4.69kWh in 31mins = 9.08kWh.
Maybe this is correct due to the losses involved.....I can't remember if the quoted maximum onboard charger power is for actual power used vs power put into the battery.
Anyone know?

 

[Cocijo]

I really wonder how accurate some of these charge ponts are - especially as they charge by the electron! Are they regulated/subject to checks?

 

[Barney]

This might be nonsense, but I'm new to all this so here goes anyway ... that's the charger saying it has delivered 4.69kW. Can you see what the car thinks it received ?

 

[MundaneMatt]

Well, I don't yet have an OBD2 sensor fitted so I'm not sure, but it did increase the charge by a notch on the HV battery gauge, and the GOM increased by 16 miles of range.

 

[Alb]

Looks like the charger is giving erroneous readings.
You may have been overcharged (and I mean money not energy!)

 

[Kithmo]

Are you sure you were only 30 minutes, not maybe 45 with the first 15 minutes free ?

 

[Cocijo]

I wonder if some chargers round up amounts by 15mins for example or have a min charge time?

 

[JodyS21]

This might be nonsense, but I'm new to all this so here goes anyway ... that's the charger saying it has delivered 4.69kW. Can you see what the car thinks it received ?

Unfortunately not, it's very annoying.
Even via the OBD2 data, you cannot query the batteries current capacity in kWh, all you can see is the (real) SoC%.

If we knew for absolute certainty what 100% real SOC was in kWh and that 0% real SOC was zero kWh, then you could calculate how many kWh are available in the battery. (Dependant of course how SOH impacts this...)

During the actual charge, you can monitor the amps that are going into the battery (assuming that's where those amps really are measured in the whole circuitry), based on this and the current voltage that can be seen, you could calculate how many kW are being put into the battery at a given point in time, measuring it for the whole charge period would then tell you how many kWh has really been put into the battery. But how accurate these readings would be, I do not know. I think this is the way that some of the apps monitor the kWh.

I've seen articles quote efficiency for the AC-DC converters of between 70-90%, what it really is in the ZS who knows.

 

[Coulomb]

4.69kWh in 31mins = 9.08kWh.

I think you mean = 9.08 kW, not kWh. I note that this would be an average power; instantaneously it might have been more or less than that. But most likely at these rates, it would have been uniform.

that's the charger saying it has delivered 4.69kW.

The charger is saying that it delivered 4.69 kWh of energy, since they charge for energy delivered, not how fast it's delivered (kW).

It's certainly puzzling. If it's grossly over-stating the energy delivered, then that's concerning, especially when the energy use is presented with a resolution of 0.01 kWh.

I believe that the MG's charger is capable of delivering some 6.6 kW (not the 7 or 7.2 often quoted). There might be an average of about 200 W charging the auxiliary (12 V) battery, running pumps, computers, etc. So that's about 8.9 kW into the charger. That would make it 100% x 6.6 / 8.9 = 74% efficient, which seems way too low.

Even if it was delivering 7.0 kW, that's still 79% efficiency, very low.

Perhaps there is more like 500 W of overhead, and it really can deliver 7.0 kW. Then assuming the EVSE's claimed energy delivery to be accurate, that would be 100% x 7.0 / 8.5 = 88% efficient. That's more respectable, but I'd actually expect more like 93% efficiency, give or take about 3%.