Re:Street-Legal ebikes are underpowered
by Johnny555 on Thursday December 29, 2016 @06:41PM
(#13281229)
Define "almost as much energy". Bike motors aren't super efficient, especially at low RPM's (like when you're coasting to a stop).
A bike has very little rolling resistance, nearly all of the energy used to propel the bike on level ground is going toward fighting air resistance. Even on rolling hills, I rarely use my brakes on the downhill, any regen braking used on the downhill is just going to increase the energy needed to go up the next hill. (and due to less than perfect efficiency, you lose energy on both the regen capture and powering the motor again, so it's a big loss).
So yes, you might recover some small amount of energy used to decelerate the bike at a stop sign, it's not going to be significant percentage of the total power requirements, and you're going to be paying a price in dollars, complexity and weight for this feature.
The most unusual thing I ever saw in my EV days... We had a full Ford Focus Electric on a chassis dyno to debug some problems. After several hours of tuning and data collection we realized the car needed to be charged to get it back to our own facility. The dyno place had no high power chargers. So we set the dyno somewhere around 40mph, put the car in drive and left it. With no foot on the gas it would do a light regeneration at that speed. The strange part is that we sat around a table to analyze the days data about 5 feet from the car. We're at a table next to a car tied down and going 40mph and its almost dead silent charging via regen. Analysis done, car charged, untie it and off we went ;-)