Unlike most e-bikes, the Brompton's battery is integrated into a bag that sits on the front of the bike. While that detracts slightly from the classic, streamlined design, it's handy as it can be unclipped for charging or riding as a regular bike – it's probably one of the easiest to ride without battery assistance thanks to its weight. The battery also powers two lights for safe commuting.
Electric Motor. Having a battery that will last long is just one piece of the puzzle. The electric motor should be powerful enough to move the bike on flat surfaces without any problems and to overcome some low-steep slopes. It will help you out on steeper slopes, it won’t let you down. If the motor or “the engine” is more powerful you’ll be able to accelerate faster and to reach a higher momentum. This will allow you to reach your destination faster and without you getting tired.
"Bargain Buys" Most electric bikes priced less than $600 at big box retailers and on-line are aimed at the kid/teen/toy market. They generally lack the performance and durability that people want and expect. Also, parts and service can be problematic with both big box retailers and on-line vendors. We urge you to invest in a quality e-bike, preferably from a local dealer, that will serve you (and others) for many years. Remember, if it's poorly constructed and you can't get repair parts, it will likely become land-fill material. Save, beg, or borrow the money to get a quality bike or kit.
After you decide which style of e-bike you want, consider the class. In the US, there are three classes defined by the type of assist and how fast the motor will propel you. Most electric bikes sold are class 1 or 3. Class 1 bikes have a motor (max 750w) that assists while you're pedaling, up to 20 mph. Class 3, also known as “speed pedelec” can also have up to a 750w motor, but it can assist you up to 28mph. Both of those are allowed in most states and cities without license. Class 2 have throttles that don't require you to pedal to get a boost. They're allowed on most streets, bike lanes, and paths, but less popular than the other classes and not covered much here (because we still love to pedal and the greater distances pedal assist bikes can cover).