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Bike+ light hybrid system unplugs the e-bike for a Prius-like ride


October 10, 2013

The Bike+ is scheduled to hit the market next year

The Bike+ is scheduled to hit the market next year

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Determined to mimic the efficiency-boosting approach of non-plug-in hybrid cars like the Toyota Prius, Italian manufacturer ZeHus has developed a small, lightweight e-bike system that optimizes cyclists' efficiency. The hub-based unit aims to add exactly the right amount of electric propulsion to create flowing, seamless rides without the huffing, puffing and walking.

The e-bike systems that we're used to seeing use large batteries that require external charging, much like plug-in hybrids. Seeking to make a more self-contained system, ZeHus looked to lighter hybrid cars like the Toyota Prius for inspiration, creating an e-bike system that doesn't need to be plugged in. As in the Prius, onboard hardware such as regenerative braking keeps the battery charged.

The Bike+ system is designed to create a smoother, more efficient bicycle ride. Like a parallel hybrid car, it manages output from its two power plants – the cyclist and the battery-powered electric motor – to maximize efficiency. If you think about the average bicycle ride, there are typically parts of the ride where the cyclist is huffing and puffing slowly uphill, perhaps even walking the bike, and parts where he or she is pedaling along with ease. Bike+'s aim is to smooth out those highs and lows into a more continuous, efficient effort.

The Bike+ uses several different sensors and an algorithm-based ECU to optimize efficiency. A pedaling sensor and slope-estimating triaxial accelerometer monitor cycling conditions and pedaling efficiency. When the cyclist is pedaling at high efficiency, such as when he's cruising at a constant speed on flat ground, the system siphons off a small amount of that energy by adding negative torque. ZeHus says that the cyclist will barely notice the difference, if he notices it at all. The captured energy is stored in the battery and saved for when the cyclists' efficiency dips, at which point the 250-watt rear hub motor will kick in, adding a boost to his or her pedaling. The system's algorithm is designed to deliver motor power without completely draining the battery.

In effect, the cyclist's pedaling is a bit harder during easy stretches and easier during intense stretches, such as sustained ascents, making for a smoother, more uniform effort. A regenerative brake replaces the bike's standard rear brake, adding another form of energy generation.

The system's algorithm works on several principles, providing the most motor assistance during intense muscle efforts (i.e. acceleration and hill climbs), tapering off assistance as a cruising speed is approached, switching to negative torque-based energy recovery when a cruising speed is reached, maximizing recovery during braking, and providing the best balance of efficiency and battery charge to ensure that power is available when needed.

Thanks to its onboard charging mechanisms, the Bike+ is able to recharge on the fly and doesn't have a limited range like e-bikes that rely solely on external charging. ZeHus does admit that it's possible to drain the battery completely, such as when the cyclist chooses the maximum motor assistance available in the Pedelec mode. However, it promises that the charging process is quick and efficient once the charging systems are able to get back to work. There is a charging port for convenience (three hours), but the idea of the Bike+ system is that it can be a self-sustaining system that doesn't rely upon external electricity.

E-bike users should note that in the same way light hybrid cars don't have as much electrical power on tap as plug-in hybrids, the Bike+ isn't as powerful as Pedelecs and other traditional e-bikes.

All of the Bike+'s hardware is integrated into a fairly compact rear-wheel hub system that weighs around 6.6 lb (3 kg). The 160 Wh li-ion battery pack surrounds the motor, and the pedaling sensor is built into the freewheel mechanism. Because all of the hardware is mounted to the rear wheel, there aren't any extra wires or components around the frame.

The Bike+ also includes an integrated Bluetooth module, which works with an accompanying smartphone app. The app allows the cyclist to monitor the system during his rides and also allows for tweaking the system. ZeHus also plans to give the app a social component, letting cyclists share their rides and locations.

The work behind the Bike+ system began in 2010 at the Technical University of Milan (Politecnico di Milano), producing a prototype a year later. The electrical system has since evolved and triggered the founding of ZeHus as a company. The production version was introduced at the Eurobike show this past August, and ZeHus plans to get it to market by early 2014.

Source: ZeHus

About the Author
C.C. Weiss Upon graduating college with a poli sci degree, Chris toiled in the political world for several years. Realizing he was better off making cynical comments from afar than actually getting involved in all that mess, he turned away from matters of government and news to cover the things that really matter: outdoor recreation, cool cars, technology, wild gadgets and all forms of other toys. He's happily following the wisdom of his father who told him that if you find something you love to do, it won't really be work. All articles by C.C. Weiss

I'd love to see a motorcycle equivalent of this. Where you could have a relatively low output engine that would suffice for cruising speeds but with significant electric boost for blasting away from lights or passing. A difference though to a human/electric hybrid could be that whilst stopped at the lights the motor could actually be working a bit and juicing up the system (super capactitor?) rather than just idling there doing nothing. By launch time (green light), hopefully you've got energy to burn until you reach cruising speed. At cruise, just like this bicycle version, the motor could work a bit harder than it needs to (at times) to store an energy buffer if required. It could be quite fun.


Unless Im missing something the Bionx system is a plugin system with big battery. This is different. They probably should leave the plug off to distinguish it but this weighs less than half the Bionx, uses a smaller, built in battery and doesn't rely on plugin charging. Seems Theradarsweep missed the point, this makes some of the improvements mentioned.

Joe F

It's an alternative to what already exists in the bionx kit and so nothing terribly new. There's significant room for improvement in this product space: more powerful, faster, more torque or efficient motors ; better software management of the power, charge etc ; lighter product ; ease of fitting to bikes.... Looks like the battery on this cannot be removed for charging and that's going to be a show-stopper for many people who don't have access to power where they lock up their bikes ; I don't believe for a second that this product will "be a self-sustaining system that doesn't rely upon external electricity." - you'd need a lot of regenerative downhill and braking to charge a battery, even on as small as this. Busy market place: they will be competing against some very strong products. My guess: wont succeed.


Why not use another hub on either the bottom bracket or front hub?

Tony Johnson

The "downside" to pedelecs is that a person may be encouraged to use the battery more than they "should." Sometimes it is nice to have a moped-like phase in one's daily trek. But making use of gravity and intertia to supplement rather than supplant one's efforts may have a niche.

Bruce H. Anderson

I guess this is a great fail safe for any country in which somebody would like to own or operate an ebike...The really low rolling resistance from this type of bike would enable the rider to reach cruising speed in a very short amount of time.

Terry Hope
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