Sagging Voltage while charging the car at 14 Amps

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databeestje

Well-known member
Joined
Nov 24, 2015
Messages
83
Location
Netherlands
When I am charging my i from either a public EVSE or the one at home, with my own cord or the provided J1772 plug I can see the voltage sagging which is monitored by the OVMS I installed into the car.

To clarify, I live in NL, so the grid voltage is ~230 Volts. When the charge is near complete I see 227 Volts and 2 Ampere, but when the charge starts I see 211 Volts and 14 Ampere. So somewhere under load I'm losing ~10 volts in the wiring before the charger sees it. Could I have a bad J1772 Inlet, or is the cable from the J1772 inlet to the onboard charger much thinner then the rest.

With basic 2,5mm squared cross section the voltage drop at 14 Amps would be about 2 Volts per 10 meter of cord. So that should still be quite close to the input voltage.

Since I see this on all the various chargers, and with different cords and plugs, the only wiring and plug left is the one in the car.
 
I see this drop, too. My car holds about 244 volts under load, but goes up to about 250 volts at the top.

I'd say they have the minimum gauge wiring in the cable going to the charger. They should have 12 gauge wire, but probably have 14 gauge.
 
databeestje said:
To clarify, I live in NL, so the grid voltage is ~230 Volts. When the charge is near complete I see 227 Volts and 2 Ampere, but when the charge starts I see 211 Volts and 14 Ampere. So somewhere under load I'm losing ~10 volts in the wiring before the charger sees it.
Maybe it should be 230, but even when lightly loaded (2 amps) it's only 227 and when fully loaded with 14 amps it's 211, so you're actually only losing about 6 volts, or less than 3% which is well inside accepted tolerances - In other words, it's nothing to worry about

I agree it's more likely the wiring to the EVSE and probably not the wiring in the car

Don
 
Don, he's losing 16 volts, not 6. At the worst, I've only noticed a 10 volt drop, and that was at a station with weak service (I can't remember where, though). It had a 208 volt circuit feeding it, but the car was only getting 198 volts.
 
Don't forget, the voltage drops are in each of the two wires, so the total voltage drop is doubled. I tend to agree with Don that it's nothing to worry about. BTW, does it really draw 14A, as the maximum I've ever seen is less than 13A at 208vac-240vac?
 
You might try to scan or feel around for something getting warm, such as the handle or the connector socket (from the backside access cover) or the wires to the on-board charger (lift the motor cover for access). By your numbers it would seem that something is heating up with about 200 watts.
 
In Norway we have this socalled 230V IT grid. My charge voltage is often below 220V while charging at 8A. And I dont think there is somrthing wrong in either cases. Other loads like heating owen inside or a neighbour using the waterboiler also affects the local grid voltage.. I do also blive that the furter you are from the grid substation the higher the voltage can fluctuate.
 
Yeah, I did another test by switching on the Oven at home (~2kW) and I also see my grid voltage sagging just below 220. I don't think I am particularly close to the substation, so that could well be right.

I just found it odd to see it at other chargepoints too. Anyhow, I'll keep an eye on it and see if I can pop the compartment when it's a bit warmer again. The 14A current is reported by OVMS, so I'd guess it's about right. My EVSE says it can use 16A, but it doesn't quite. In my power consumption stats on PVoutput I see it drawing a steady 3000 Watts either way.
 
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