CHAdeMO charging efficiency

[ruby110]

I charged at a Greenlots CHAdeMO station today. Charged from 55% to 90%. The Tesla reported 26kW added. Greenlots reported 28.8kW used. I'm surprised at the efficiency loss. That is about the efficiency I expect from 240v level 2. Greenlots agreed that this is an efficiency loss.

BTW, the charging experience was great!

 

[glhs272]

Huh. I wouldn't think you would see that much charging loss between the shunt on the battery and the shunt on the charger. It's just a wire between the two (more or less). That brings up an interesting question. Will charging stations be required to pass annual exams for accuracy like a gas pump would? After all you have to pay for the energy (not a concern with a supercharger), could it be inaccurate and therefore ripping you off? Will we be seeing "inspected by the state of such and such"s weights and measures"... type stickers on them (i.e. regulation)? Edit, I guess I forgot about the conditioning system that's running, so it makes sense. But still a valid question.

 

[ruby110]

Good question. Charging was free in this case. All we paid was $2.50/hour for parking.

 

[stopcrazypp]

Is the 28.8kWh AC electricity or DC? If it's AC, then 90.2% efficiency is already fairly decent. (Do note that you missed the h in kWh, which is required if you are talking about energy instead of power).

Greenlot's presentation on their chargers say a AC-to-DC conversion 10% loss is to be expected.
http://www.advancedenergy.org/porta.../Greenlots-DCFC_NCPEV-Webinar-Dec-09-2014.pdf

 

[RiverBrick]

Do we know how Tesla rounds off its figures? Can 26 kWh mean, 25.5 kWh, 26.5 kWh or even 25.0001 kWh or 26.999 kWh?

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Will charging stations be required to pass annual exams for accuracy like a gas pump would? After all you have to pay for the energy (not a concern with a supercharger), could it be inaccurate and therefore ripping you off? .

I am aware of two ABB Terra 53 (dual standard CHAdeMO-CCS Combo) stations that would be undercharging for kWh, except they bill by the hour. They state 10-15%% less than what appears on the Tesla dash. For instance, Tesla says +47 kWh and they say, "energy furnished 40.6 kWh."

 

[ruby110]

@stopcrazypp, you're correct I forgot the h: 26kWh vs. 28.8kWh. CHAdeMO is DC. I also forgot about the ambient temperature: it was in the high 80s. I'm now guessing the energy difference was due to cooling the battery during the charge.

I believe the energy displayed during charging is to the tenth place but the summary is rounded to integers. Is that correct?

 

[widodh]

@stopcrazypp, you're correct I forgot the h: 26kWh vs. 28.8kWh. CHAdeMO is DC. I also forgot about the ambient temperature: it was in the high 80s. I'm now guessing the energy difference was due to cooling the battery during the charge.

I believe the energy displayed during charging is to the tenth place but the summary is rounded to integers. Is that correct?

The point is, do they measure on the AC or DC side of the charger?

I think the measure on the AC side of the charger, so you pay for the conversion to DC losses.

 

[wcalvin]

Probably just the IR drop in the pipe.

 

[ruby110]

In this instance I didn't pay directly for the energy used regardless of how it was measured. I payed for the parking. Other Greenlots sites charge by time. My interest in the efficiency actually has nothing to do with DC charging. I use a 14-50 outlet and my UMC at a resort and I pay the resort for the electricity I use which I have to estimate. I understand charging at 240v is about 90% efficient but this 14-50 is at 208v. I think there other losses like heating or cooling the battery. I'm just trying to understand how to estimate better. In the end, I just err on what I think is the high side so not to cheat the resort.