Four new models of chainless ebikes, by French manufacturer Cixi, will be for sale at Eurobikes 2025. We analyze the pros and cons of one of the most interesting innovation for ebikes drives. Pedals turn directly an electric generator. The electric energy thus produced is then transmitted to the rear hub motor. What would be barely sufficient to conveniently propel the ebike only especially on climbs. Nevertheless there’s also a battery. So these ebikes are like normal ebikes, without pedal powered mechanical propulsion, but with a battery recharged by pedaling.
Standard battery ebike drive systems vs. chainless digital drives
Let’s compare pedaling efficiency of a standard ebike with pedaling energy recovery system, or PERS, pedaling energy recovery system, as CIXI, its manufacturer, calls it. We already wrote here about Schaeffler, which produces another chainless ebike drive system, and the chainless Mando Footloose folding ebike. Such is rather a comparison between normal pedaling efficiency and pedaling energy recovery efficiency. Indeed, a chainless electric bike totally lacks the power coming from pedaling, whereas its hub motor can well be supported also by a battery, as happens in most cases, e.g. the ebike pictured below. Provided that the battery can well support regeneration while delivering energy. That can accelerate its wearing, like happens with the BMW i3 electric car. Its gasoline powered range extender accelerates battery wearing, to the point that BMW discontinued its production.
- Cixi-equipped Heritage Chainless Altitude ebike
- Cixi-equipped Heritage Chainless Altitude specifications
Chainless ebike advantages vis-à-vis normal ebikes
- Lighter transmission system
- No drivetrain wear and tear, no greasy fingers
- Smooth and fluid automatic gear changes with infinite gear range
- Low running costs, low maintenance
- Charge while you ride
- Wheel lock
- Anti-lock braking
- Eliminates crank dead spots, optimizes your pedaling technique
- More new ebike design options
- Environmentally friendly
- Performance in diverse terrains
Chainless ebike disadvantages
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1. Lighter transmission system
The electric generator thrusted by pedaling weighs something less than a kilogram. Chainring, cassette, derailleur, chain and battery of a normal ebike can easily exceed 5 kg.
2. No drivetrain wear and tear
Because there are no wearable mechanical transmission parts.
3. Smooth and fluid automatic gear changes with infinite gear range
Its software harmonizes the electric motor thrust with riding conditions, e.g. terrain nature and inclination, weight, etc.
4. Low running costs, low maintenance
Brakes last longer because of regenerative braking by the motor, no need to change, clean and lubricate chains, chainrings etc.
5. Charge while you ride
By pedaling and regenerative braking, thus prolonging ebike range.
6. Wheel lock
It blocks the rear wheel to prevent theft.
7. Anti-lock braking
This is made possible by gradual regenerative braking.
8. Eliminates crank dead spots, optimizes your pedaling technique
As we pedal, there are spots in the pedals loop where it is more difficult to exert pression, e.g. when the two pedals are at top/bottom position. With a digital drive, that is avoided. It can even harmonize the required effort with the different strength of your legs, should one of them be stronger than the other.
9. More new ebike design options
The absence of chain, chain ring and cassette broadens the choice of ebike designs, for instance for foldable ebikes.
Chainless Mando Footloose folding ebike
10. Environmentally friendly
Environmentally friendly, wearing the battery less. By optimizing battery usage and enhancing energy recovery, regenerative ebikes contribute to reducing energy consumption and emissions associated with electricity generation.
11. Performance in diverse terrains
Regenerative systems can be particularly beneficial in hilly or urban areas with frequent stop-and-go scenarios, where the opportunity for energy recovery is more significant.
CIXI Verdant, chainless e-cargo bike
Chainless ebike disadvantages
1. Lower drive efficiency, roughly 20% less
On a normal ebike, energy deployed pedaling is converted for a good 95% into kinetic energy, resulting in the rear wheel rotation and bike propulsion. 5% loss is due to mechanical components friction: chain, cassettes, pedals and chainring. If pedaling strength is used to feed a generator, like in a chainless ebike, there is one more conversion between mechanical and electric energy than with a battery ebike. The motor of the latter converts the electric battery energy into mechanical energy, whereas the former converts mechanical energy of pedaling into electricity which is then converted back into mechanical energy by the motor. The process of converting pedaling energy into electrical energy results in 20% loss of energy by the generator. That is, the pedaling energy is transmitted to the wheel at a 95% rate by a chain, whereas that rate drops to 80% when turned into electricity by a generator to feed the motor. We then must shave 20% off that 80%, because an electric motor converts into movement or kinetic energy only 80% of the electric energy it receives, the remaining 20% being turned into heat and lost by friction. Altogether, only 64% of the muscular energy applied to a pedaling electric generator is transmitted to the wheel.
Electric generators convert mechanical energy into electrical energy, but in the process, some energy is inevitably lost. The key areas where energy loss occurs include:
1. Mechanical Losses: These losses arise from friction in moving parts such as bearings and air resistance (windage losses) within the generator.
2. Copper Losses: Occurring in the windings of the generator, these losses are due to the resistance of the wires, often referred to as (I^2R) losses, where (I) is the current flowing through the windings and (R) is the resistance.
3. Iron Losses: Also known as core losses, these are due to the alternating magnetic fields within the iron core of the generator. These include hysteresis losses and eddy current losses.
-Hysteresis Losses: Caused by the lagging of the magnetic field strength behind the magnetizing force in the core material.
-Eddy Current Losses: Caused by circulating currents induced in the conductive core material by the alternating magnetic fields.
4. Stray Load Losses: Such losses are typically minor and arise due to leakage fluxes and non-uniform current distributions.
5. Brush and Contact Losses: In generators that use brushes, losses occur due to the contact resistance between the brushes and the commutator or slip rings.2. Inadequate for a range of riding situations where changing gears is necessary
When a lot of energy is required, e.g. when riding on steep and long climbs, chainless drives assistance can barely provide the necessary quantity and duration of energy. They are thus inadequate for mountain biking.
3. We can’t pedal without support
Just like on a classic VAE on which you’d choose to switch off the motor when you don’t need it, or simply when you’ve drained your battery.
Look Rover 45 chainless speed pedelec powered by Cixi
A successful example of using mechanical energy to produce electricity instead of movement
Nissan’s e-POWER technology is a unique hybrid powertrain that utilizes an electric motor to drive the wheels, while a gasoline engine serves as a generator to charge the battery. This setup enables the car to offer electric driving experienceswithout the need for external charging. Sales of Nissan e-POWER vehicles have generally been strong, especially in markets like Japan, where the technology has gained popularity. Models equipped with e-POWER, such as the Nissan Note and Nissan Serena, have seen favorable reception. In Europe, the popular Qashqai and X-Trail models are equipped with such technology. The demand for e-POWER is driven by consumers’ interest in their better fuel efficiency and reduced emissions while retaining the convenience of a traditional gasoline engine.
Nissan Qashqai
Conclusion: if manufacturers succeed (or have succeeded?) in improving electricity generators to the point of transforming a very high percentage of pedaling energy into electricity, chainless ebikes will enjoy a bright future.
Images: Cixi, Heritage Ebikes, Nissan
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As the owner of an e-bike with nonfunctioning pedals I’ve been wanting a way to charge the battery from pedaling. Is the generator for sale separately?
Hi Charles,
Unfortunately, no.
Cheers,
Luca