Hybrid cars: where an HEV gets its energy

Useful to know

The HEV hybrid car uses an internal combustion engine and one or more electric motors. The electrical part receives energy from a battery, but in this type it is not charged by connecting to an external electrical network. The charge is operated within the vehicle. This distinguishes the HEV from the plug-in hybrid and is the first clarification we have to make when different cars are presented with the common name "hybrid". [1]

One of the important processes is delay recuperation. The electric machine can work as a generator and some of the energy is directed to the battery. Instead of all the corresponding energy being lost on braking, a part is saved for later use. Another source of charging is the operation of the internal combustion engine. Therefore, internal charging does not mean that the car creates energy out of nowhere or that fuel consumption has ceased to matter. [1, 2]

The battery and electric motor can assist in starting and accelerating, and the control allows the internal combustion engine to be switched off in certain situations. According to the AFDC, the additional electrical power could allow the use of a smaller engine. For the driver, the result is a joint work of components, not two completely independent cars in one bodywork. The exact timing and power distribution depends on the design and control system. [2]

There is a difference between a soft and a full hybrid. In the description of the AFDC, the soft hybrid system supports the engine, but does not drive the car alone with electricity. A complete hybrid can use electric motion for limited distances and under certain conditions. This does not warrant assuming the same electric range for all models. Even similar designations in advertising material do not replace the technical information about the specific vehicle and the mode to which the promise relates. [2]

The way of connecting is also important. In a parallel hybrid scheme, the internal combustion engine and electric motor can supply mechanical power to the wheels. In a serial scheme, the movement of the wheels is electric, and the engine is involved in the production of electricity. There are different implementations and combinations. It's useful to think about the energy path instead of just counting the engines. Thus, it becomes clear why a system can behave differently in the city and with prolonged movement. [2, 3]

When comparing to a non-hybrid car, similar sizes, equipment and conditions of use should be considered. The mere presence of a battery does not prove how much it will be saved for a particular owner. For example, a person with daily short city trips has a different mode than a person who spends almost the entire run on a long route. Understanding HEV helps to ask the right questions about these cases: when the system recovers energy, when it assists the engine and how the final fuel consumption is accounted for.