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Multiple EV points?

alanblaby

I do occasional maintenance for a local hotel. 100A 3 phase incomer.

I was there this week and noticed they had had 4 EV chargers fitted in their car park. Now, the cable supplying the DB they have fitted, was fitted by me 2 years ago. They have taken out a newish Hager DB to fit a Fusebox one in its place. No idea why they'd do that, as it would have been easy to buy new Hager RCBOs and surge devices. Anyway, the cable is 10mm 4 core. How on earth do they run 4 chargers off that, as well as the (minor) loads for the bar area? Is it usual to have load protection/limitation on such an array of chargers?

And on a similar point, the total load required by the hotel isnt great, electric cooking, partial panel heating, but adding 4 chargers seems to be getting toward the limit of the incoming supply. Is this negated by the load limitation devices (if fitted)?

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  • I think that more information is required - type of cable, reference method, make and model of EVCP, etc.

    The most conservative CCC of a 4-core cable is 50 A per phase - Table 4D4A RM D.

    I assume that the chargers are 3-phase, else one phase would have two of them.

    If the chargers are set to a maximum of 7 kW, that is (7000/230)/3 = 10.1 A per phase, so not a lot of headroom for the other loads.

    I suppose that in due course, if not currently, all four chargers could be in use for up to, say, 14 hours (18:00 until 08:00). That would be 7 x 14 x 4 = 392 kWh. At 25 p/unit, that comes to about £90 per night. I wonder how much the hotel will charge their customers?

  • in reply to Chris Pearson

     I wonder how much the hotel will charge their customers?
    Enough to pay for the supply update they will eventually need I imagine.

    Quite often these things are installed and operate by a third party franchise outfit who install the machines and handle the billing but then pay the site owner by the kWhr plus a small base rent that varies with the location.
    The EV owner then pays through one of the standard apps.

    Joking aside, if they are properly networked, and if they are or not is perhaps a moot point, it is certainly possible to set a group of commercial chargers like that up to play nicely together and to wind the amount the car can demand up and down to stay at some target load level, and even to ensure that all vehicles in a mesh of chargers get an even share of the high current time. If folk are charging overnight at the hotel, and this is known, the requirement is not really for  all to be on at once. They can be parked in the bay but now fully charged, if the requirement is just to be ready to go by breakfast time, then it's not such a bad load profile and may fit in with the hotel not being at peak load as well, by making sure charging is tailing off before the other loads like boiling water for breakfast related things and so on  are coming on.


    Mike.

  • in reply to Chris Pearson
    Chris Pearson said:
    If the chargers are set to a maximum of 7 kW, that is (7000/230)/3 = 10.1 A per phase, so not a lot of headroom for the other loads.

    Are we sure about that? The chargers might be three-phase, but if Mode 3, the vehicle is likely to be single-phase, so setting to 7 kW = 30.5 A at 230 V, or, because vehicle internal chargers on Mode 3 have switching converters, if you use the maximum volt-drop in BS 7671, giving a voltage range on ESQCR supply at the charging equipment of +10 % / - 11 %, you might get up to 34.2 A (instead of the maximum of 33.1 A you might expect with a linear load and +10 % supply voltage variations).

  • in reply to gkenyon
    gkenyon said:
    The chargers might be three-phase, but if Mode 3, the vehicle is likely to be single-phase

    As far as I can see, the vast majority of vehicles have an on-board charger limited to 11 kW (TP) and 7 kW (SP). I assume that the on-board charger will use all three phases if they are available.

    Only a few cars can draw 22 kW, and some basic models can only use SP. Some vehicles are limited to 3.7 kW.

    If you go with 11 kW (TP), that is 16 A/phase, which potentially exceeds the CCC of the OP's distribution circuit. However, from the installation manuals that I have seen, the output can be limited to a lower value, which is why I suggested 7 kW (TP).

    If they have not limited each EVCP, then Alan's concerns are entirely justified.

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  • in reply to gkenyon
    gkenyon said:
    The chargers might be three-phase, but if Mode 3, the vehicle is likely to be single-phase

    As far as I can see, the vast majority of vehicles have an on-board charger limited to 11 kW (TP) and 7 kW (SP). I assume that the on-board charger will use all three phases if they are available.

    Only a few cars can draw 22 kW, and some basic models can only use SP. Some vehicles are limited to 3.7 kW.

    If you go with 11 kW (TP), that is 16 A/phase, which potentially exceeds the CCC of the OP's distribution circuit. However, from the installation manuals that I have seen, the output can be limited to a lower value, which is why I suggested 7 kW (TP).

    If they have not limited each EVCP, then Alan's concerns are entirely justified.

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  • in reply to Chris Pearson
    Chris Pearson said:
    As far as I can see, the vast majority of vehicles have an on-board charger limited to 11 kW (TP) and 7 kW (SP). I assume that the on-board charger will use all three phases if they are available.

    This is not the case. The vehicle might be three-phase (up to 11 kW) or single-phase (up to 7.4 kW).

    A single-phase EV only uses one phase ... L1 in the vehicle inlet. Until recently, most EVs are single-phase only. Three-phase support is being implemented for quicker charging at Mode 3 now.

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