Charging speed puzzle

quilkin · Dec 18, 2024

I just tried my new MG5 with a new type 2 cable at a public charging station for the first time (I've charged at home with teh granny cable without a problem). I'm going on a long trip at the weekend so wated to make sure it all worked.
So I plugged into the 'Shell Recharge' point at my local Aldi and charging started. But after 46 minutes the system had only added 2.59 kWh (accordng to the app - only 3% extra on my car display). It's supposed to be 7 kW with my (single-phase) cable. The car dash was showing power at '-7' amps, which works out at just over 2 kW - the same as the granny charger.
I'll try another charging point tomorrow, but wondered if I have a problem - maybe the cable is defective?
BTW the Adli charger was very cheap - 21p per kWh - cheaper than at home at peak times!

cambo1982 · Dec 18, 2024

What was the car at before you started... alot of the fast chargers here in Ireland taper down REALLY agressively once it's over 80% charge.

quilkin · Dec 18, 2024

cambo1982 said:
What was the car at before you started... alot of the fast chargers here in Ireland taper down REALLY agressively once it's over 80% charge.

It was at 74% -

Coulomb · Dec 18, 2024

My guesses:

You ended up with a 16 A cable
The EVSE (Shell Recharge "charger") is rated at 16 A, possibly three phase, but your car only uses one phase.

2.59 kWh / (45/60)h = 3.38 kW. That's about 14 A at 240 V. With losses and other loads, that's about right for a 16 A single phase supply.

Edit: Can you see any writing on the cable? E.g. 3G x 2.5 mm² means three wires of 2.5 mm² cross sectional area, which is only capable of 16 A. There will be a resistor in the cable that the car senses, and reduces the charge current so as not to overload the cable.

quilkin · Dec 18, 2024

Coulomb said:
Edit: Can you see any writing on the cable? E.g. 3G x 2.5 mm² means three wires of 2.5 mm² cross sectional area, which is only capable of 16 A. There will be a resistor in the cable that the car senses, and reduces the charge current so as not to overload the cable.

The cable says '3G6 + 1 x 0.75' . It is a single-phase cable.

5teep · Dec 18, 2024

It's possible the charger was set to output a lower current, the store might not have enough free power to charge at 7kwh, but it could be your cable yes. If you bought it online go back and check what the listing actually says for it.

quilkin · Dec 18, 2024

I've done a bit of reseach and it seems that an 11kW EVSE will only provide ~3.5 kW for a single-phase cable. Is that correct? If so I was ill-advised as to what cable to buy by the supplier.

5teep · Dec 18, 2024

quilkin said:
I've done a bit of reseach and it seems that an 11kW EVSE will only provide ~3.5 kW for a single-phase cable. Is that correct? If so I was ill-advised as to what cable to buy by the supplier.

No, if the cable is capable of carrying 7kw** then you should get that. Not all single phase cables are made equal though and you need to carefully read the listing info to be sure the one you buy is correct.

/edit ** There's a resistor in the cable connector that tells the charger what rating the cable is so the charger will not provide current above what it can take.

MickeySw · Dec 18, 2024

quilkin said:
I've done a bit of reseach and it seems that an 11kW EVSE will only provide ~3.5 kW for a single-phase cable. Is that correct? If so I was ill-advised as to what cable to buy by the supplier.

Yes, a 11kWh (3phase) EVSE will only provide around 16A per phase, i.e if you have a 7kWh single phase cable, around 3.5kWh is all you get.

In order to get the full 7kWh with your single cable you need to find either a 22kWh (3phase) or a single phase 7kWh EVSE.

If you want to have a ‘one fits all cable’ you need a 3phase 22kWh version. This will allow you to charge @ 7kWh on single phase or @ 11kWh on 3 phase EVSEs

Charging speed puzzle

quilkin

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quilkin

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Coulomb

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quilkin

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