Perfect? Sorry, but it’s not that simple. No e-bike will be perfect for every commuter and use-case, but there is an optimal electric two-wheeled vehicle for you. This primer will help you select an e-bike that satisfies your functional requirements and falls within your financial constraints.
Local E-bike shop to the Rescue
An important first step as you begin your quest is to find a dealer who will be a partner in your decision. An e-bike represents a substantial investment and the dealer must make your interests the top priority. Because the dealer will be your interface with the manufacturer for warranty issues and may perform some of the maintenance on your bike, you will want someone you consider reliable and trustworthy. Fortunately, SoCal has excellent shops with knowledgeable employees and great e-bike selections. They are eager to have you test their products since they know that once you’ve ridden an e-bike, you’ll be enthralled with its utility. Some shops rent e-bikes and it might be feasible to explore this avenue for additional input.
Hub-Drive, Mid-Drive, Sex-Drive
The propulsion systems that predominate the e-bike market are “hub drives,” where the motor is encased in the front or rear hub. In mid-drives, the motor is incorporated into the crank-set. In general, front and rear hub motors are preferred for flat or mildly hilly terrain and mid-drives for steep ascents. A rear motor is used for most hub systems, but a front motor means a lighter-weight bike and can be an excellent choice for cargo applications with the added front weight balanced with a rear cargo load.
Hub motors are an excellent choice for many applications since the motor is contained inside the wheel and doesn’t accelerate wears on the drive-train. They are either of two types, direct drive (DD) or geared. The DD motor is a rudimentary system having only one moving part in which the axle is held and the body of the motor spins. The one disadvantage of DD’s is they are usually large and heavy for their power output. Geared motors are smaller since they have gearing inside the hub which reduces the high speed of the motor to the low speed of the hub. They are also much lighter than DD motors and as a result usually have better acceleration. Their disadvantages are they have many moving parts which are subject to wear and they dissipate heat less effectively than DD motors.
Mid-drives are very effective for hilly areas since they multiply the output of the gearing system at the crank-set. This allows the rider to use the bike’s transmission as the motor’s gears and the engine operates in an optimum RPM range to exhibit more efficient use of battery power. Additionally, they provide better weight distribution by being centrally located in the lowest part of the frame. They are usually more expensive than hub motors and result in increased drive-train wear.
The Electronic Brain
The controller, the brain of an e-bike, converts the direct current (DC) voltage of the battery to an alternating current (AC) form that can be used by the motor. Typically, controllers have a low voltage cutoff (LVC) to prevent the battery from over discharging, sensors which measure the position of the motor, and shunt resistors which limit the amount of current being transferred to the motor. This last feature insures that the battery isn’t overstressed and the
motor doesn’t get excess current which could cause it to overheat.
Batteries range from 24 volts (V) to 48V. The maximum speed of an e-bike is roughly proportional to voltage. For hub motors 24V, 15 mph; 36V, 18-20 mph; 48V, 28 mph. Mid-drives are set for 20 mph or 28 mph maximums depending on their classifications. The amp hours (A/h) of a battery, usually 10 A/h to 20 A/h relate to “the gas is in the tank”. A 36V, 10 A/h battery has 360 (36 X 10) watt hours, and can propel a 170 pound rider on flat terrain with no wind and mild pedaling about 15 miles on a bike with a hub motor. Higher voltage, more A/h, a lighter rider, downhill road, tail wind and vigorous pedaling will increase mileage while the converse is true. Mid-drive mileages should routinely average at least 25 percent more than hub motors.
Now you’re prepared to relate your requirements to an e-bike shop and continue your education by road-testing the models they recommend. This primer has only scratched the surface of the many terms bandied about like brushed and brush-less motors, regenerative braking, “turns” of copper in the motor, back electromotive force (EMF), hall sensors, field-effect-transistors (FET’s), sine-wave and square-wave controllers as well as many others. Good luck and enjoy the journey as you find your very own optimal e-bike. -BB
Some key questions to consider:
What is your price range?
Do you have a flat or hilly commute?
How far will you travel?
What is your desired speed?
Will you be carrying cargo? Or children?
Do you need to take your bike up stairs?
Is taking your bike on a train or bus part of your commute?
Are you able to charge your battery at work?
Do you want pedal assist (PAS), throttle or both?