Same EVSE model different charge rate

[Blue20]

I am one of those lucky one have access to multiple EVSE at the workplace. I notice that not all EVSE charges at the same rate. They are all the same model (Eaton level 2 240V 30A) side by side (same environment).

For example, yesterday my car was at 50% (from BMWi app). With one EVSE, my car said, charging would finish in 6 hours. I unplugged the EVSE and tried the one in the next stall. With the second EVSE, my car said it would finish in 2.5 hours. In between, I didn't change any setting in my car.

Any idea what that may be ? Is there anything I can do to force maximum charging rate?

Mine is a BEV, with original software version.

 

[jadnashuanh]

The EVSE sends a signal to the car, and that indicates how much power it can provide. Then, the car knows how much it can draw. If the EVSE's pilot signal (don't quote me on that named signal!) isn't reporting properly, the i3 won't ask for more. It could be that's how that particular one is programmed, or it may not be capable of providing 30A on both ports, or the ground is not good, and the car can only draw a lesser amount. Or, it's broken!

 

[Blue20]

Since it is a handshake to agree on the charge rate, how can I tell it is the EVSE that is broken and not my i3?

 

[kevinb61]

Since it is a handshake to agree on the charge rate, how can I tell it is the EVSE that is broken and not my i3?

I guess by the fact you changed EVSEs an then it worked as expected you can hope it's just the particular EVSE.

 

[RJSATLBA]

It might be worth trying the same 'test' using the same pair of chargers in the opposite order.

 

[jadnashuanh]

FWIW, take a close look at both plugs and see if you can detect any corrosion on any of the pins...a dirty connection might affect the car's ability to read the signal accurately. The EVSE only announces how much power it has...the car then decides how much of that it wants to take. If the EVSE is wrong, and is reported low, the car won't know, and will adjust itself (think sort of like a dimmer switch - the car's in control, not the power line). IOW, it is the vehicle's responsibility to not draw more power than the EVSE said it can provide...if it DOES ask for more, that's what circuit breakers or fuses are for...those would protect the device, but the EVSE does not otherwise restrict the power it provides...essentially, it just has an on/off switch in that part...it's the control signals on the other lines that do the rest of it, and the car makes the determination on how much it draws. The car WILL adjust the charge rate based on the temperature of the batteries, the current charging rate, and how close to 'full' they are, so it will taper off near the end, and depending on other conditions, may throttle back at other times as well if things were getting warmer than it wanted.

Note, if it's cold outside or too hot, it might divert some of the power to preconditioning the batteries to allow for full rate charging, and that circuit is probably (I don't know for sure) a fairly low draw. IOW, if you looked at a chart of the charge rates, it may be moving up and down depending on conditions.