How much is a battery charge?
The price varies of course according to the capacity of the battery and the price of the power provider. All in all, it can be stated that it costs about 10 to 15 cent to fully charge the rechargeable battery of a standard pedelec. This is a price to which your boss will certainly not say "no", if you want to charge your pedelec from time to time at your company to be able to ride home with drive.
How do I find out before the purchase how efficient the rechargeable battery of a pedelec is?
The capacity, i.e. the energy content, of a rechargeable battery is indicated in watt-hours (Wh) in the technical specifications of a pedelec. The greater the figure, the greater the battery capacity. Unfortunately, many manufacturers show off with ampere-hours (Ah) instead of watt-hours. This figure alone is however not enough. To obtain the actual energy content, the ampere-hour figure must be multiplied by the drive voltage (in volt). A sample calculation: 11 Ah at 24 volt equal 264 watt-hours – the battery capacity is inferior to a battery with only 9 Ah, but a 36-volt-motor, i.e. 324 Wh.
Is it only the rechargeable battery that is responsible for different ranges?
Unfortunately, it is the same as with fuel motors in cars: The size of the tank does not necessarily correspond to the range. The range actually depends on many factors. In technical terms it is the motor’s power consumption and the battery management system. But the rider is a factor of at least identical influence. The chosen assistance level and hence the own physical effort as well as the shifting behaviour determine the range just like the rider’s and the luggage weight, the tyre pressure and the kind of the terrain. Quite often couples cycling together and with the same pedelec wonder why one of the batteries is empty whereas the other one is still half-full. Now they know that the rider with the empty battery had relied more upon the work of the pedelec and less on the own physical forces.
What is a battery management system?
The battery management system (BMS) controls and regulates all processes in the rechargeable battery. During the ride the system prevents too high currents from flowing out, ensures the even discharge of the cells and prevents the system from becoming too hot. A good BMS can double the service life of a rechargeable battery. One of the particularly important points is the temperature control: Heat does not only make the cells wear down faster, it may result in a self-ignition of the rechargeable battery in the worst case. During long or especially steep uphill climbs the BMS switches off the motor, as soon as a critical point is reached. Although this causes annoying stops during the trip from time to time, it protects the rechargeable battery from failure due to excessive heat and the rider possibly from injuries. The quality of a battery's BMS cannot be stated from the outside, but there are indications. A detailed display with precise battery charge status and range indication indicates a good BMS. If there is only a small control unit with a switch on/off button and a few light-emitting diodes, which is often the case on low-priced pedelecs, it is most probable that the BMS is not very sophisticated.
Author: Dirk Zedler