ICEV cars run at very low levels of energy efficiency at ALL speeds, so the same range/efficiency penalty produced by air resistance at higher speeds is often less apparent to the driver, than with a BEV. Operating in the most efficient narrow RPM range for an ICEV engine will give much greater efficiency, so, if properly geared, an ICEV vehicle may lose little range/mpg by increasing speed up to (legal) freeway speeds, and final drive ratios are often set to realize this benefit.
Unlike an ICEV, the LEAF drive train is within a few percent of maximum efficiency in a very broad range, from about 4,000 to 9,000 RPM, which if i correctly recall the calculations done by others previously, is about 35 to 85 mph. You could shift the LEAF efficiency curve to the right (higher speed) by altering the final drive ratio, but the tiny gain in drive train efficiency, would only be at very high speeds, and be nearly insignificant.
If you take a look at the drive train efficiency curve drees posted yesterday he took from P 17/18 here:
http://www.electricauto.org/resource/re ... e_2_11.pdf
Look at the vertical scale on the same chart. It seems the LEAF is only significantly lower than optimum efficiency in high torque demand/low speed operation. Shifting the curve to the right by altering the final drive ratio would decrease the efficiency in these conditions, probably more than offsetting high-speed gains.
So at low speed, a light foot is your best "range extender", and the best "range extender" at high speeds, is avoiding high speeds
, and the large aerodynamic drag penalty incurred.
As I said in your "drive home" thread, for trips exceeding single charge length (until we get DC charging) the slower you drive, the faster you will get to your destination.
nader wrote:Granted I am new to EV's and still have a lot to learn but doesn't a motor turning at lower RPM consume less electricity? Hence all of these newer cars having a tall top gear to improve mileage at highway speeds. I imagine Nissan chose a gear ratio that gave a decent top speed and acceleration while staying within the motors efficiency range. My question is if I was willing to give up some acceleration on the bottom end could I make enough of a difference in power consumption on the top end by having the motor turn at a lower RPM.
As far as tire size changes that isn;t going to make much difference. You can't go with a much larger overal diameter than the stock 25" diameter before you'll run into clearance issues with struts, fenders etc.