Charger Efficiency

[EVBill]

Does 84% sound about right for the efficiency of the Rav4 EV charger?

I averaged 3.4 mi/kWh each of the last two days of my 80 mile round trip commute. Dividing 80 by 3.4 I get 23.53 kWh used each day.
Both days I charged at a Chargepoint station and the website says I used 28 kWh each day.
Therefore 23.53/28.0*100%=84%

 

[TonyWilliams]

Does 84% sound about right for the efficiency of the Rav4 EV charger

Yep, that's about right.

There isn't a single efffiecenty value, since the temperature of the battery, the SOC%, the internal impedance (degradation), charging speed (volts*amps), etc, all play a role in that efficiency percent.

 

[rav4buyer]

Does charger inefficiency have to do more with the EVSE and our electrical utilities, or the actual charger in the car? If it's the charger in the car then we should all have about the same inefficiency (given the same variables below) is that right?

The way I calc'd it was:
I charged 32.9KWH in 5hrs 20 minutes = 6.17 KW
I have a 30A EVSE with 240V = 7.2KW

6.17/7.2KW = 85.6% efficiency

This seems in line with EVBill's figure.
On a side note, a full 80% SOC in 5hrs 30mins with a 30A charger seems really good relative to the stated charging times.

 

[Dsinned]

Of course, there is always some "loss" associated with the utility's distribution of electricity to a residence through the wiring. Losses associated with an "EVSE" (Electric Vehicle Supply Equipment) probably are significantly less than the losses in the "charger" in the car itself. That "charger" facilitates an AC to DC conversion of electricity, with an inherently greater loss, and lower efficiency than an AC to AC device that is basically transformer-less. What's interesting is when the EVSE operates at 120Vac, the overall efficiency of the recharging process will be even less.

 

[miimura]

The RAV4EV runs coolant pumps and things the whole time the car is charging. 120VAC or low current 208/240VAC charging takes longer so more of the power from the wall goes to pumps and fans instead of going into the battery. That reduces the overall charging efficiency. The AC loss between the meter and the wall is negligible in the whole scheme of things. Most of the loss is probably in the AC/DC conversion as heat generated in the on-board charger. More total time and lower input voltage all leads to lower efficiency.