Orchard said:
Thanks guys for the links. Very interesting topic. What got me thinking about this is when people talk about their "range reduction with elevation". Sometimes it is confusing to me at first glance, when what they really saying (I think) is: the range was reduced whilst driving their EV from a lower elevation to a higher elevation. This does not mean at the higher elevations the EV's theoretical range from there on is less, when in fact it should be slightly higher.
Yes, the main elevation issue usually discussed is driving up and down hills. One uses more energy to get up a hill than is gained going back down a hill, even with a bit of an assist from regen braking. That reduces range versus driving the same speed and distance on a level road. And it matters a
lot whether one blasts up a steep hill at high speed (high power usage) versus climbing a hill slowly, which is more efficient [empirical observation].
This is a reason why anecdotal reports of "range" don't have much meaning for those of us who drive hills all the time (and there are a number of us here at MNL). It also makes "Guess-o-meter" numbers completely ludicrous.
So basically someone living in Denver will have a slightly (about 5%) higher range in their LEAF than someone driving a LEAF on the coast given the same temperature, humidity, and terrain.
The altitude improvement to range is generally quite a bit higher than 5% in Denver, but it depends on speed. At freeway speeds the range increase is considerable. At 25 mph it would be negligible. This is because drag increases at (approximately) the square of velocity. At freeway speeds drag is the dominant force slowing the car down, requiring a lot of energy from the battery to hold constant velocity. Below about 35 mph other forces, such as the rolling resistance of the tires and friction in gears and bearings, become more significant.
So, the range improvement at higher elevations will vary with speed, but it can be considerable. And it doesn't seem to be widely appreciated by many who live at low elevations. (It is the secret of those of us who live in Colorado, Utah, and high mountain parts of California.)
If you are interested in the effects of drag, you can play with it yourself if you can find a stretch of level (not just flat:
level) road with a high speed limit. You can measure how much power it takes to hold a constant velocity using the console energy meter, at various speeds from 25 to 65 (or 75, if that's possible). You should get a curve, as opposed to a straight line.