PiP: Measuring Charging Loss

Yes, that would be the range 13.6-15.7%.
Too bad the EV ratio screen doesn't list kWh usage with decimal rounding nearest tenth.

First time I used my Kill a watt on my EVSE, a single full charge was lower than the average at 11.7% charging loss.

 

You can interpolate by watching when it clicks over and noting the odometer to a tenth on the approx last 5 miles till you do a final read. Then when done you know your typical wh/mile and adjust. This gets your actual kwh consumed better than within 0.1. (0.1 kwh is about 0.5 miles)

Mike

 

I'm tracking energy use at the wall with a Kill-a-watt, but where do I go to find out how many kWh the Prius accepted? 3.15 kWh seems to be the normal full charge consumption.

With gas prices so low, I'm only saving about $0.02 per mile over gasoline. I'm averaging $0.04 per mile on gas, and maybe $0.02 per mile on electricity. Of course, my savings will double once gasoline prices double.

 

so,you've cut your transport costs by 50%?

 

For the first 10 miles of a trip, anyhow. My first drive in the car was from Gresham to Portland. The second was Portland to Bend and back. The first 500 miles were all HV since I didn't have a charging cable. I think my EV ratio is 5%, but I hope to improve this. I'm writing the environmental dept at work to see if they will install an outlet to plug into. They are an industrial customer of electricity, so their cost per kWh is about $0.04

I'm doing better than cutting transportation costs by 50%, considering my TSX only gets 30 MPG. Even at these low fuel prices, my transportation cost is 1/3 using electricity over gas in the TSX.

 

If you mean usable energy, Wikipedia states 2.73 kWh.

usbseawolf2000 in an earlier thread calculated the same.

"Just confirmed today. ICE kicked in at 23.1% SOC.
EV window is 85% to 23%. Usable is 62% of 4.4 kWh.

2.73 kWh usable."

 

If gas doubles and your per mile costs go from $0.04 to $0.08 then your savings go from $0.02 to $0.06...which is triple.

Mike

 

I hope my figures aren't accurate. I've measured 34 kWh at the wall with the Kill-a-Watt and the Prius shows 26 kWh for 146 EV miles. That's a 30% loss! One question though; does the EV miles used get reset when I reset Trip A? If so, that would account for the crazy loss. I reset Trip A whenever I gas up.

I'm getting 5.6 miles per battery kWh, and a more accurate picture of 4.3 miles per wall kWh. Granted, I save the easiest miles for EV use, so even this is a distortion of EV performance vs gasoline. If I jumped on the highway and did 60 mph, my EV efficiency might be as low as 3 miles per kWh. I'd be curious if someone has data on freeway EV use.

 

ev miles and kWh are on your ratio screens 1 and 2.

 

The ratio screen, where the EV miles used are shown, are reset separately by holding the "Trip" button while viewing that screen. Note that just pressing the Trip momentarily will toggle between two separate aggregators, both totally independent of the "Trip A" reset you do on the consumption screen. Hope this helps.

 

I am reading the original post as trying to figure out the deviation of the kWh display on the EV ratio screen from the real, from wall, consumption, in order to know what multiplier to use on the displayed kWh for our calculation of MPGe etc. Not necessarily charging and battery losses as we do not know what the displayed kWh is programmed to show nor its accuracy.

My iteration is:
My grid is 230 VAC, I have a kWh meter dedicated on the EVSE line and installed in my electric distribution box near the house meter so I can read "payable kWh" of charging. The EVSE is switched off when not in use.
I have a trip of less than 24 km (return) I am taking regularly which I am doing EV only in temps above about 17 degC, from observations I know I am doing about 9.5 km per kWh displayed in this trip at about 20 degC arriving with less than1 km left on the estimate. At this temp I am using about 2.5 kWh (displayed) per trip.
I have made a test of 2 trips combined (yesterday and today both at 20-22 degC) and tried to reach home from the second trip just when the reading flips from 4 to 5 kWh so I know this is exact 5 kWh, so today I made an extra 'around-the-block' small cycle and managed to reach parking spot about 50 m after display flipped to 5.
Meter reading: start 1500.23 kWh (full battery before trip 1). Finish 1505.60 kWh (full after trip 2).

So, in my case, if my meter is not cheating on me (I doubt) 5.37 kWh metered produced 5.00 kWh on the display - 7% deviation (from top).
Below is my EV ratio screenshot after the test.
note: the 47 km shown is in fact 47.7 km (23.8 km first trip and 23.9 km second, as displayed on the summary screen appearing after shutting down).



EDIT April 19, 2015:
I have added a third trip to the combined calculation to reduce uncertainty. This time not my regular trip.
Temp is 22 deg C and once again I have managed to reach parking/charging spot just when the display changed from 6 to 7 kWh so I know it is 7.00 kWh exact.
Meter reading: start: 1500.23 kWh, end: 1507.86 kWh so "payable" 7.63 kWh.
So, with my car I can say more certainly that the reported consumed energy is lower by 8% that actual.



EDIT April 23, 2015:
Further tests over 10 kWh show that actually my kWh display is about 9-9.5% lower than actual...my first 5 kWh test above was exceptional low, probably misreading of my meter?

 

What's interesting us the "fuel saved" number makes no sense to me. I can't quite tell from the photo whether that's gallons saved or liters saved, but 47km is 30 miles or so. Clearly, 1.5 gallons would be ridiculously high petrol consumption. But converting the 1.5 to liters, that's .396 gallons. That equates to 75mpg (as calculated by the car, not measured or extrapolated, since he's 100% EV).

Can anyone explain that?

 

Sorry the photo is not completely focused but it's liters.
Remember that 1.5 could be also 1.599. As for the calculation I have no explanation but to say that Toyota is conservative...

 

I have edited my post #31 above today by adding a third trip to the combined calculation and can now confirm with more certain that my displayed kWh on the ratio screen is 8% lower than my "payable" kWh.
See post #31 above for details

 

^ I want to take further measurements to be absolutely certain before referring it to the said thread.
Will update my findings shortly.