October 27, 2021

Millions of people across the world bought bikes during the pandemic. For some, it was a means of transportation and a way to avoid buses and trains. For others, it was a form of recreation. 

But even in this hot market, e-bikes were an especially bright spot, with U.S. sales alone tripling in 2020.

While they are popular, they aren’t new. In fact, e-bikes have a long history. Patents for the earliest models were issued 120 years ago. So what’s made them so popular now? The answer lies in new technologies that make them faster, safer and longer-lasting.

Three Key E-Bike Technologies

Batteries: The earliest lead-acid batteries were extremely heavy. Over the years, technologists and engineers have experimented with new battery materials that can store more energy in smaller areas. Research in the 1990s on nickel-metal hydride batteries offered a range of about 60 miles. Today, most bikes rely on high-density lithium ion cells that can store more energy in a more compact footprint and have ranges that exceed 100 miles. The energy density of leading Li-ion batteries has doubled in recent years, while the cost per unit of energy has fallen by more than 70 percent, according to “Electric Vehicles and the Magic 8 Ball,” which appeared in the March 2017 issue of IEEE Electrification Magazine.  

Electric motors: Like batteries, electric motors have been around for a long time. The earliest electric motors relied on brushes, which provided electrical contact in the fast-spinning commutator. Because these fixed parts were in contact with moving parts,  they wore out and required maintenance. Brushless electric motors, introduced in the 1960s, have consistently  evolved to produce more power with smaller and smaller designs. Today’s electric motors for e-bikes rely on a brushless design and powerful, rare-earth magnets to create drive systems that require very little maintenance. 

Torque sensors: The vast majority of e-bikes sold around the world are known as pedal assist bicycles or “pedelec” bikes. The defining feature of these bikes is that the rider has to pedal for the motor to engage, and the motor assists the biker, but doesn’t do all the work. That’s a big benefit to urban commuters, and it also helps people travel longer distances without getting fatigued. 

It would be dangerous for an e-bike motor to apply full power at the slightest hint that the pedal was moving. Pedal assist e-bikes need a sensor to detect when a pedal is moving. Older e-bike models have simple cadence sensors that interpret rapid pedaling as a demand for more power, but that isn’t great going uphill, where a rider might be forced to pedal slowly while needing a bigger assist. The solution: torque sensors that detect the amount of force applied to pedaling. Chief among these technologies are magnetoelastic torque sensors. In this design, the bicycle’s crankshaft is magnetized in a specific direction, surrounded by a sensor that measures the torque applied to it through pedaling.  

Moving Forward

The industry has significant momentum. Luxury carmaker Mercedes and motorcycle brand Harley Davidson have both developed e-bikes. What remains to be seen is whether people will use them to replace their automobiles, or reserve them for recreational use.

In major cities, a boom in e-bikes has led to a push for more bike lanes. But there’s also a push to make e-bikes safer with technology, like sensors that can predict the trajectory of a car, and warn either the rider or the driver of an impending collision with sound. 

The increased adoption of e-bikes “requires redesigning cities to be more bike-friendly,” said IEEE Senior member Simay Akar. “Data analytics technologies can aid smart and green cities planners’ efforts. Policy measures and structural socioeconomic modifications are some of the most important potential key elements of this transition and offer the potential to maximize the benefits from the transition.” 

Learn More: Interested in converting a regular bicycle into an e-bike? Here’s how.  


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