right speed is the killer. but also you can use more battery if y0u are a really strong rider because the harder you can push the more them motor helps. I have been sick a lot and I measured how this works on my Bosch powered bike. like if I averaged less then 120 watts (my output) or above 150 watts I would use less juice then 120 or 150 watts. I didn't to see a bit increase when I was close to 200 but its been a long time since I could do that.