B) Petrol cars change gears at high RPM as the efficiency of the motor is better at lower RPM (also quieter, longer life) electric motors are more efficient at higher speed usually
The below two quotes were from this link http://www1.eere.energy.gov/manufacturi ... 097517.pdf
what i found interesting was that it was important to match the motor to the car. i understand that there are mainly 9 & 11 inch, and some electric motors are built for torque instead of speed.
mathematical equations from the above link (to work out) is on page 3from the link just above wrote: Most electric motors are designed to run at 50% to 100% of rated load. Maximum efficiency is usually near 75% of rated load. Thus, a 10-horsepower (hp) motor has an acceptable load range of 5 to 10 hp; peak efficiency is at 7.5 hp
here is another link i found really interesting about efficiency and motors
but it is too technical for me to work out.
the question i had originally, is what is the maximum efficiency of an electric engine - in relation to changing gears to go faster.
for example, from the above quotes and links - i would assume that a 10,000 RPM electric engine would use the least amount of battery power at 7,500 RPM.
or have i got the wrong end of the stick here
i would appreciate people's thoughts here - as i would like to get the most out of batteries.