palmermd said:
TickTock said:
There is another explanation for the range in the chart - variability in the economy meter due to instrumentation accuracies (i.e. gids). So you may be only getting 4.0 mpkWh when your meter indicates 4.5.
Now this is something that I think could be on the right track. In fact this may explain the variability of the results displayed on the dashboard of the vehicles in the test. But the cars SHOULD have consumed at the exact same rate given that they were all travelling on the same road at the same time with cruise control set to the same speed using the GPS.
Precisely!
Which is what I was saying last night:
...And how do we know that the Phoenix test conditions resulted in all of the cars (or even any one of them) using precisely 4 m/kWh, so that the test distances observed are even valid for a direct comparison to the 76-84 miles at 4 m/kWh Nissan
estimate?...
IMO without valid and accurate m/kWh reports, the only way to calculate capacity variability in a
single LEAF is by recharge (As TickTock has been attempting) or in repeated range tests under closely controlled conditions, as I have been trying to do.
If you want to try to determine comparative capacity from a range test, Such as was attempted in Phoenix, you should:
1: Normalize all variable charge capacity factors, battery temperature during the charge cycle being the largest one I am aware of.
2: Normalize all variable efficiency factors: Which I believe the test was quite well-designed to do.
However, by not using the Carwings reports to monitor driver efficiency, valuable data on how well "driving style" was normalized, was lost.
CW reports the drivers total kWh generation by regenerative braking over every trip. Regen use lowers overall drive efficiency. I suspect even the most efficient Phoenix drivers, who avoided virtually all friction braking, had to use
some regen, to decelerate during the test, due to traffic conditions. Records of how this report of how efficiency varied
between the different drivers, should always be noted, not only in a multiple vehicle test, but to monitor the variable driving efficiency, in repeated tests of a single LEAF.
3:Monitor recharge capacity, with the same charge capacity variables controlled as was done during the charge session prior to testing.
It is true you that by doing so, you are measuring the energy used to "refill" the battery, not the amount you used during the test, so any BMS variability will also come into play here. But, IMO, the great advantage of this approach, is that there are far fewer variables you need to control for, than in a range test. That is why I a have recently begun to try to monitor both.
If you can accurately calculate your capacity from charging data, a range test to determine capacity reduction from any standard (measured or theoretical) would seem to be unnecessary,
other than to determine how LEAF efficiency varies between cars, or over time.