A micro hybrid uses an automatic start-stop system to recuperate braking energy and store it in a classic 12 V starter battery. However, the vehicle is driven exclusively by an IC engine, making it a questionable inclusion in this category.
Unlike micro hybrids, mild hybrids do have an electric motor in the drive system, as well as a 48 V battery to accompany the standard 12 V battery. However, this engine never works on its own and is used only to support an IC engine by boosting the engine during acceleration, for example. Fuel consumption tends to be lower than in non-hybrid vehicles.
In a full hybrid, or Full Hybrid Electric Vehicle (FHEV), an electric motor and an IC engine can be used together or interchangeably. While it is possible to drive using only the electric engine, a low range tends to make it feasible only for very short trips. Unlike mild hybrids, full hybrids do not have an additional 48 V battery, opting instead for a high-voltage traction battery with several hundred volts, while the engine also tends to be more powerful.
As the name suggests, the batteries of plug-in hybrids (Plug-in Hybrid Electric Vehicle, PHEV) can be charged using a charging station or a wall socket alongside the traditional recuperation system.
Parallel hybrids use two drive systems simultaneously or individually whenever required. With this type of drive system, the powers of the electric motor and the IC engine are added together.
Series hybrids have an electric motor and an IC engine connected in a series but, unlike parallel hybrids, have a single drive system. The two engines will not be mechanically connected. Generally, the electric motor is used to power the vehicle, while the IC engine generates electricity for the battery.
Range extender concepts, in which the IC engine is used only to recharge the battery when it is empty until the driver can find a charging station, also fall into this category.
Power split hybrid
Both of the previous models can be combined in a single vehicle, known as power split or series-parallel hybrids. Here, it is up to the driver to decide which system they prefer to use.