A standard Hybrid electric vehicle (HEV)
primarily utilises the combustion engine. However under heavier loads it works together with the electric motor to minimise fuel consumption, conserve energy, and even recuperate energy in some particular driving situations (e.g. cruising, braking, stopping, etc.). The battery is charged either by the combustion engine or by energy recuperation.
As a result, fuel efficiency is greatly increased. Especially for stop-and-start city driving.
What’s a PHEV (Plug-in Hybrid Electric Vehicle? And what are the benefits compared to an HEV.
A Plug in Hybrid Electric Vehicle (PHEV) works similar to, and has all the benefits of, a HEV. But you can also charge the (much bigger) PHEV battery externally to allow it to drive for more than 50km on full Electric mode. If the battery is la little low it simply reverts back to normal HEV mode and “self-charges” through the engine or energy recuperation.
A PHEV in full EV mode can typical save you more than €3 per 100km driving when compared against a HEV running at 4.5l/100km. So for someone who drives 50km, or less, each trip you can get all the benefits of a Full Electric vehicle while having the option to change to HEV on longer journeys.
People often talk about hybrid cars giving you “the best of both worlds”, and that is absolutely true: A hybrid vehicle is able to switch between both powertrains or make them work together to always deliver the solution that powers the car forward with maximum efficiency.
As mentioned above, when in full electric mode a PHEV simply uses the battery and electric motor to do all of the work. But when the battery is low it reverts back to normal hybrid mode.
Let's take a closer look...
When driving off from a stop position
Whenever accelerating from a stationary position, up to a speed of approximately 25 km/h, hybrid cars are powered by the electric motor (which draws on the battery power). This is one reason why hybrids are particularly efficient during city driving.
When driving at moderate speed
Whenever cruising, hybrids are powered mainly by the combustion engine – as this is when it works most efficiently. During this time, the engine can also power the generator, which recuperates electricity used to recharge the battery for later use.
When accelerating strongly
Whenever you have your foot down firmly on the accelerator pedal, both the combustion engine and electric motor work together to increase power to the wheels. This is thanks to the power-split transmission, which combines the torque output of each powertrain at the same time.
When braking or cruising
Whenever you apply the brakes or take your foot off the accelerator pedal, hybrid cars make use of a system called “smart regenerative braking”. So hybrids do two things: they stop feeding power to the wheels, and use the power of the rotating wheels to recuperate energy while slowing down the car. This produces electricity which again is used to recharge the battery for later use.
When coming to a complete stop
Whenever you apply the brakes with the intention of stopping completely, hybrids completely turn off both the combustion engine and electric motor. The battery power is used to keep operating any other vehicle systems you might need (like your radio, or headlights, etc.)