Strong hybrid system

A strong (or self-charging) hybrid can move the car on electricity alone, which separates it from the mild hybrids that Maruti and Hyundai badge on many cars. The best-known layout is the series-parallel system used by Toyota and shared with Maruti: a petrol engine, two motor-generators and a small high-voltage battery, all joined by a planetary power-split gear instead of a conventional gearbox. The engine drives the carrier, one motor-generator sits on the sun gear and the wheels (with the second motor) on the ring gear. Varying the generator's speed changes the gear ratio continuously, which is why the spec sheet says e-CVT.

• Setting off and crawling: the engine stays off; the battery drives the traction motor.
• Cruising: the engine runs at an efficient speed, and part of its power turns the generator to top up the battery.
• Hard acceleration: engine and motor push together.
• Braking: the traction motor runs as a generator and slows the car, recovering energy that a normal car wastes as brake heat.

The battery is small, a fraction of an EV pack, and is never plugged in. The driver notices silent starts, an engine that switches on and off without fuss, and city mileage that is often better than highway mileage, the reverse of a normal car. In India the Toyota Innova Hycross, Urban Cruiser Hyryder, Maruti Grand Vitara and Honda City e:HEV use strong hybrids (Honda's e:HEV is a series type: the engine mostly generates and a motor drives). Cost is the catch: the hybrid parts add a lot to the price, and taxation treats them like petrol cars rather than EVs.