First time rapid charge on my MG ZS EV

[Deleted member 2439]

That’s an interesting thought you’ve raised.
I had assumed that when on a DC charger, the power (kWh) shown on the chargers was what had been supplied to the car (in DC) not what the charger had/was consuming in AC.
Some Googling to be done here....

Essentially the losses will be inside the charger, but I’d wager that the unit displays consumed AC power. They certainly ain’t going to give you something for nothing!

 

[JodyS21]

Essentially the losses will be inside the charger, but I’d wager that the unit displays consumed AC power. They certainly ain’t going to give you something for nothing!

I've spent some time googling and can't find anything that talks about whether it's "gross or net" power consumed.

It seems wrong to me that they charge you for AC consumed, as they could use a very inefficient converter and the consumer would have to pay more etc. But then they'll want to make the most money they can.


It should be reasonably easy to work it out, by looking at the figures when doing a DC charge, unfortunately I won't be doing one for ages now to be able to look at it.
If the actual charger shows the voltage and amps and kWh, then it can easily be checked if the Volts X Amps = kW. Alternatively if it's not displayed on the charger, the volts and amps could be seen on the cars dash.

 

[JodyS21]

I've spent some time googling and can't find anything that talks about whether it's "gross or net" power consumed.

It seems wrong to me that they charge you for AC consumed, as they could use a very inefficient converter and the consumer would have to pay more etc. But then they'll want to make the most money they can.


It should be reasonably easy to work it out, by looking at the figures when doing a DC charge, unfortunately I won't be doing one for ages now to be able to look at it.
If the actual charger shows the voltage and amps and kWh, then it can easily be checked if the Volts X Amps = kW. Alternatively if it's not displayed on the charger, the volts and amps could be seen on the cars dash.

Just found a photo I took from a DC charger last month:
104 Amps
431 Volts
44.82 kWatts
104 X 431 = 44,824

So it does measure and charge for (net) DC kWh provided, not the (gross) AC kWh consumed.
That's good.

 

[Deleted member 2439]

Just found a photo I took from a DC charger last month:
104 Amps
431 Volts
44.82 kWatts
104 X 431 = 44,824

So it does measure and charge for (net) DC kWh provided, not the (gross) AC kWh consumed.
That's good.

Fair enough - so it looks like the inefficiency of the charger is being absorbed within their “small” markup of the power they purchase!

 

[Gomev]

You got a 73% charge then (31.2/42.5).
Plus your initial 21%, you ended up with roughly 94%

At the initial 21% displayed in car this is fairly close to the 'real' percentage, in car display and real SOC diverge more towards the top of the range.
So the 21% reported remaining plus your calculated 73% to get 94% SOC actually adds up to pretty much the 100% that would be displayed in car due to the 7% buffer at the top.

 

[JodyS21]

At the initial 21% displayed in car this is fairly close to the 'real' percentage, in car display and real SOC diverge more towards the top of the range.
So the 21% reported remaining plus your calculated 73% to get 94% SOC actually adds up to pretty much the 100% that would be displayed in car due to the 7% buffer at the top.

Hang on I calculated that on only the supposedly usable 42.5kwh not the full real supposed 44.5kwh, so those figures are for the fake/displayed %.

In reality, it added.....70% (31.2/44.5)

BTW Here’s the formula if anyone needs it (for the new BMS):
Real % = (Displayed % X 0.91) + 2
Displayed % = (Real % - 2) / 0.91