DaveinOlyWA said:
Randy said:
So u think u are gettting near 100% charger effiiency?
Charger efficiency is nowhere near 100% if there's any validity at all to the Carwings measurements. There are some misconceptions at work here.
The "consumption" figure in the downloaded spreadsheet version of carwings is the traction motor consumption. It does not count regen (or accessories). It's coincidence that it matches the electric meter value. You can see this by looking at the Carwings "energy economy" in the same spreadsheet - it's way higher than the actual wall to wheels measurement. The accessory value is not even show in the download, but it is reflected in the Total Used column (ie total used is consumption - regen + the not-shown accessory amount).
The reported figure of 3.88 miles per kWh wall to wheels is very good. Our car appeared to be getting about 3.2 early on...yesterday we got about 3.7 over 52 miles, in part I believe to improved technique. Carwings is overoptimistic for sure, or maybe a more accurate description is that it does not take into account charging or regen inefficiency. Dave is charging at L1 I believe, and he's getting somewhat lower wall to wheels (relative to me, Randy or Jimmy) - I think there's evidence that L1 is somewhat less efficient than L2 - of course weather/terrain etc. could factor in as well.
If we believe the net consumption figures from Carwings, then charging at L2 could be construed as less than 70% efficient. For example, according to Carwings we supposedly 'Used' 8.8 total kWh yesterday to go 51 miles, or 5.8 kWh per mile. "Consumption" (carwings spreadsheet) was 13.6. The 8.8 is that consumption (traction motor) - regen + accessories. To recharge after that drive took 3.75 hours @ 3.77kW (Clipper Creek) or 14.13 kWh. Odometer actually said 52 miles, so I'm calling that 3.7 wall to wheels.
Now, my 70% assertion is simply 8.8 (the car's net claim) over 14.13. I don't think it's _quite_ that simple though, because we actually were down 7 bars, which has got to be more than 8.8kWh. So the 8.8 is misleading if not simply wrong. Inefficiencies during regen could share some of the burden with charging.
Anyway, my main point is that the consumption figure in the carwings spreadsheet is not directly related to the amount of electricity pulled through the utility meter, even though it looks close.
It is interesting that the car's own internal miles per kWh generally falls somewhere in between Carwings and measured wall to wheels. Maybe extrapolating from that figure would be a fairer measure of charging efficiency. For example the car internally claimed ~4.2 m/kWh yesterday. That would be 12.4kWh. 12.4/14.13=88%. That I could believe.