“I recently converted a mountain bike to an electric bike. The conversion went relatively smoothly, so upon completing the project, I hopped on and set out for a shakedown cruise. I kept my eye on the battery charge indicator, not knowing how far to expect the bike to run on battery power. About the time that the power meter showed 80% with me feeling pretty good, because I had gone a long ways, I ground to a halt with a dead battery. An unhappy call to the manufacturer resulted in words like Oh, the battery indicator really isnt good for much the technology just isnt there yet. I needed better than that.
I wanted to know which gear gave me the best efficiency, how much was the headwind costing in battery capacity, what power level delivers the most miles, does it really help to pedal, if so, how much? In short, I wanted to know if my battery would get me home. Kinda crucial, doncha think?
This project is a result of my long pedal-powered ride home. Basically this small module sits between the battery and the e-bike power supply input to monitor battery current and voltage. Additionally, a wheel speed sensor provides speed information. With this set of sensor data, the following values are calculated and displayed:
Instantaneous efficiency – measured in kilometers per AmpHour of battery consumption
Average efficiency – since this trip started, km/AH
Total number of AmpHours used since last charge