Application story: Smart motors from maxon make high-tech e-bikes

Use of electric bikes or e-bikes — those with power-assist and full drive capabilities — is exploding in Europe and now the Americas as more people than ever look for green modes of transportation in increasingly dense urban centers. Recently introduced to the world market, maxon motor makes an integrated drive (sometimes called a hub motor) consisting of motor, gearbox, and controller designed to convert any bike into an e-bike.

maxon offers black DT Swiss wheels in 700c and 26, 27.5, and 29-in. versions. The drive comes in installation widths of 135,142 or 148 mm for conversion to e-bikes. Photo by Philipp Schmidli.

Electric bikes in the U.S. are becoming popular not only for commuters and sport riders, but hardcore offroad riders too.

“In ten years, there will be no more commercial mountain bikes without electric motors … it’s going to be the next big thing,” said Gary Fisher, inventor of the mountain bike, at Eurobike 2015.

Many manufacturers base their e-bike drives on inefficient motors that generate a lot of heat — even though they quickly drains the batteries. In contrast, maxon’s BIKEDRIVE is a permanent-magnet ironless-core design that outperforms other options on the market, particularly in terms of power density, acceleration, heat dissipation, and efficiency. The electric drive can deliver 500-W continuous (in U.S. versions) while operating at 85% efficiency and maintaining 75% continuous efficiency even when climbing uphill.

More specifically, the maxon BIKEDRIVE is a pedal-assist drive, so there’s no throttle. The drive adds additional torque (to 50 Nm peak or 25 to 30 Nm continuous) while the rider pedals. Power is electronically limited with speed held to 20 mph in the U.S. to comply with federal regulations for e-bikes.

The maxon BIKEDRIVE also lets riders convert normal bikes into e-bikes. Here, the rear wheel motor is mounted to a DT Swiss Wheel and includes a battery, charger, cables, and a quick release or through-axle adapter for easy use.

Control of the e-bike drive is simple and intuitive through a maxon Powergrip that lets the rider pick from four twist-click positions and fifth option to turn the drive off.

Power Level 1 (10 Nm), 2 (20 Nm), and 3 (30 Nm) are continuous settings. Power Level 4 (Turbo Boost) is to temporarily accelerate over demanding obstacles or zooming out of a corner with a throttle-like feeling. The Powergrip also has twin LED indicators to show remaining battery and motor temperature.

The maxon electric BIKEDRIVE accelerates from 0 to 20 mph in less than three seconds. It lets a 175-lb cyclist climb an altitude of 3,200 ft at 10% average incline in less than a half hour.

Besides high-performance output, the way in which the maxon design is integrated makes for a physically balanced assembly.

In its BIKEDRIVE iteration, the hub is about 7 lb and the battery is about 6 lb. The whole 13-lb setup is balanced enough to let professional riders to jump their bikes. (Many early-generation e-bikes in this style are unbalanced and really heavy because of their lithium-ion batteries and motor style.) Currently theBIKEDRIVE is the only system on the market that’s compatible with the new 148-mm (Boost) hub standard and 12-speed SRAM Eagle Drivetrain. maxon is also working on even faster motors and new higher-capacity batteries.

The manufacturer makes the bike drive at its new maxon advanced robotics & systems ltd. (MARS) facility in Switzerland — including the controller, motor, gearbox, and encoder. The technology, already proven as a performance e-bike drive, will also be used for other applications.

maxon precision motors | www.maxonbikedrive.com