Chemistry determines the cell voltage (1.2V or 1.5V and there are others like Lithium at 3.0V), whether the battery is rechargeable, and how the voltage changes as the battery discharges i.e. at what voltage is the battery considered to be flat or fully charged. Switched mode power supplies. One more point.
The Average Bike Riding Speed. The average road bike speed is between 11 and 12 mph. Bike riding speeds vary widely depending on your riding conditions. When you are zooming down a paved hill, your speed may increase to over 20 mph, while you may slow to only a few miles per hour when you are climbing a steep or rocky grade.
When I ride with a couple of the locals we tend to average around 17-18mph and I find that I'm never really pushing, if I ride on my own I average somewhere between 18-22mph, depending on the route/distance.