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To gain exemption from road tax, road insurance, MOT tests, vehicle registration, the requirement of a driving licence and wearing a motorcycle helmet the speed under power is restricted to 15 miles per hour. They can of course be cycled beyond this speed.
To go faster requires more power, so a more powerful motor is required to go faster. And motors are ˇ°woundˇ± or designed to operate at a specific speed. For example, a motor that is intended for a 20ˇ± wheel must turn much faster than a motor intended for a 26ˇ± wheel to achieve the 15 mph UK limit.
Because of this, just being powerful is not enough to gain higher speed. It is possible to have a powerful motor that will not turn any faster - limiting speed.
A 160 watt motor intended for a 50 kg office lady in Shanghai who cannot go faster (by law) than 12 mph is not going to help a 90 kg European go 15 MPH. Most electric bike motors are, in fact, designed for places where people are smaller and bikes are limited in speed.
Like people ¨C as batteries age, their performance decreases. (Actually, in the first 25 or so charge / discharge cycles, many batteries get better, and then start a gradual decline).
If the battery has been poorly treated ¨C such as heavy use, the wrong charger, stored in a hot damp place, exposed to excessive cold, then the performance will suffer.
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