On 12/31/2021 4:17 AM, paul dove via EV wrote:
Well, that’s not how efficiency is measured but I think I know what you mean.
The Wh per mile is mostly a function of weight. Aero starts to weigh in around
55mph. On conversions a good estimate is weight divided by 10. My car weighs
3100 lbs with me in it and I got around 300wh/m. Tesla beat this by making the
battery a larger percentage of total weight by using aluminum. No one else
comes close. I think the Bolt is close to the rule of thumb.
At the wall is probably the best way to measure efficiency. It is
what the consumer cares about most. That is what I would care about, for
sure.
Weight doesn't make nearly the difference in efficiency as does the
frontal area.
Often, the weight of a car is sometimes reflected in the frontal
area, however, but there is not much correlation.
Rolling resistance is roughly proportional to speed (and the
weight,) while aerodynamic drag is proportional to the frontal area and
the _cube_ of speed. That cube term adds up very quickly. Aero drag
starts to dominate at about 30 mph. Nothing else matters much over ~60 mph.
Bill D.
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