Electrical system of Bicycle lighting
Batteries, either rechargeable or disposable, are often used to power electric bicycle lights. For bicycle touring, commuting or if battery operation is otherwise unwanted an electrical generator, or dynamo, may be used. (While “dynamo” generally refers to a generator that produces direct current with the use of a commutator, cycling usage normally refers to an alternating current magneto.) Unlike batteries, a dynamo has unlimited duration, but the maximum power output is relatively low. This is somewhat mitigated by good optics and slight overvolting of the lamp; a good dynamo nominally rated at 6 V is generally allowed to produce 7 V or so by its voltage limiting circuitry. In Germany, it is illegal to use bicycles without a dynamo-based lighting system except on “racing bicycles” below 11 kg. This has stimulated the market for high quality dynamos such as B&M or Schmidt.