The drivetrain of a hybrid car is powered by a combustion engine, either petrol or diesel, but one that does not work alone. It is joined by one or several electric motors that can take over or supplement its role depending on the circumstances, all the while converting the car’s kinetic energy into electricity during periods of braking.
Hybrid cars: when combustion and electric work together
Every time it’s used, a hybrid car automatically controls the actions of its different motors to provide the driver with the optimal balance of consumption and comfort. The majority of hybrid cars are, for example, programmed to start in 100% electric mode.
Thus, they guarantee that you can manoeuvre quietly at low speeds, all the while delivering rapid acceleration thanks to the torque immediately available from the electric motor.
As a general rule, the electric unit is triggered as soon as doing so is likely to lead to a reduction in fuel consumption, provided that its dedicated battery has enough energy in its reserves. The electric motor can also work simultaneously with the combustion engine, providing a useful boost in performance to overtake another car or conquer a steep hill.
Finally, the electric assembly is employed as soon as the driver stops accelerating. It then functions as a generator, operating in tandem with the engine brake: the speed lost by the car is converted into electricity by the motor and used to charge the onboard battery.
The combined operation of the different motors is automatically managed according to parameters such as speed or the charge level of the battery. The system also takes into account the driver’s needs, whether related to elements of comfort (heating, air conditioning) or the amount of pressure placed on the accelerator pedal.
The hybrid car: with or without charging
There are two categories of hybrid car which depend on the presence or absence of a charging port dedicated to feeding the electric battery from an external power source.
Standard hybrid cars, or HEVs (Hybrid Electric Vehicles), have a battery that allows them to be driven for a few kilometres only using electricity and assist the combustion engine when it is accelerating. With this model, the electrical circuit is only powered through the recovery of kinetic energy.
There are also plug-in hybrid cars: referred to as PHEVs (Plug-in Hybrid Electric Vehicles), their name emphasises the presence of a charging port similar to the one that 100% electric cars are equipped with.
A plug-in hybrid car can thus be connected to a domestic socket or a charging station in order to increase its energy stores during stops. It therefore houses a battery with a larger capacity than that of an HEV, allowing it to travel several dozen kilometres without consuming any fuel.
The advantages of a hybrid car
The exact benefits in terms of fuel economy depend on the engine specifications, the storage capacity of the electric system, the driving style and the conditions of the route travelled.
One thing is certain: hybrid cars have proven themselves to be highly efficient in cities and suburban environments. The high frequency of braking, stopping and starting again maximises the opportunities for energy recovery, and all the more so if the driver follows the precepts of eco-driving.
Renault has, for example, indicated that its Clio E-TECH hybrid, coming to market in 2020, will be able to use electricity 80% of the time for urban commutes, translating to a saving of around 40% in fuel consumption when compared to a combustion engine of equivalent power.
Hybrid car or electric car?
With or without a charging port, a hybrid car is always able to travel under the power of its combustion engine when its battery is dead. This affords it a greater operational range than a 100% electric vehicle: one large enough to meet different needs. For Renault, a historic player and leader of the European sector, the hybrid car is indeed complementary to the electric car.
Copyrights: Anthony BERNIER, PRODIGIOUS Production, Olivier MARTIN-GAMBIER
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