Series-parallel hybrid can mix and match electric and combustion power
Kawasaki is treading a lonely path as it pioneers hybrid motorcycles at the moment but it could be joined by Yamaha in the near future after the reveal of a prototype hybrid scooter.
Shown in action in a YouTube video from Yamaha Japan, the new machine takes a simple but flexible route to hybrid construction, able to operate as a pure, zero-emissions electric bike or purely on petrol power, it can also combine both for maximum performance or run its petrol engine at constant speed as a generator while powering the rear wheel electrically, to turn it into a range-extender.
The company calls the machine a series-parallel strong hybrid, as it’s able to operate as both a series hybrid – the range-extender setup where the petrol engine charges the battery for the electric powertrain – or as a parallel hybrid where the combustion engine drives the wheel with the assistance of an electric motor. The ‘strong’ part of the name relates to the fact it can work in purely electric mode, suggesting it will also be possible to charge the battery at home and only engage the combustion engine when either the battery gets flat or you need the combined power of both powertrains.
Diagrams of the system show a single-cylinder engine driving the rear wheel via a clutch and a belt final drive. There’s an electric motor/generator mounted concentrically with the rear spindle, able to directly power the back wheel and to recharge the battery using regenerative braking, and a second generator attached to the engine. In all-electric mode, the clutch is disengaged and the engine switched off, with the battery driving the motor at the rear wheel. In pure combustion mode, the clutch is engaged and the engine is running, without using the electric motor, or the electric motor can be run as well to combine the power of both. The engine can also run with the clutch disengaged, driving the generator alone to fill the battery and power the electric motor.
Although just a prototype at the moment, and clearly a long way from production, the machine shows the sort of steppingstone technology that could be essential in the future of motorcycling, given the slow take-up of all-electric motorcycles among customers.
