Article by Florian Freund

May 17, 2022
3 minutes read

“Plug-in hybrid” is on everyone’s lips. In the latest edition of our series about high voltage systems in vehicles, you can find out what this term means and how it differs from the full hybrid. We will also be looking at the comparisons between the plug-in hybrid, a purely electric one, and a hydrogen drive.


Image hybrid car

What is a plug-in hybrid?

If the high voltage battery in a high voltage vehicle can be charged via the power grid, the vehicle is referred to as a plug-in hybrid vehicle (PHEV) – it doesn't matter what type of hybrid drive is used. Logically, a PHEV requires its own charging electronics and a complex inverter. PHEV vehicles can be easily identified by the second fuel cap.

In PHEVs, the high voltage battery is generally larger, since the combustion engine is only required for longer distances or when the high voltage battery is not sufficiently charged. A larger battery means a comparatively greater electric range, but also results in a higher weight and higher costs.

The plug-in hybrid is, in a way, a further development of the full hybrid, as it has a larger battery and its own charging electronics.


image electric car

A battery that works

Compared to a hybrid vehicle, the electric vehicle has a purely electric drive and significantly fewer drive components. As an energy storage, the electric vehicle is only equipped with an high voltage battery. And since the electric motor works as a generator, the battery is charged in overrun mode or during braking.

When the vehicle is parked, the high voltage battery can be charged via the power supply. The larger the battery, the more range is possible. However, because of this, the vehicle becomes heavier, more expensive, and a complex charging infrastructure is required to ensure fast charging.


image fuel cell

H2 + O2 = voltage

A fuel cell drive is an electric vehicle that can generate electrical energy itself with a fuel cell. The reaction of hydrogen and oxygen generates direct voltage in the fuel cell. The oxygen is extracted from the ambient air, while the hydrogen is stored in a gas or liquid tank system and must be refueled regularly. In addition to electrical energy, heat and water are also generated during the reaction.

Fuel cell vehicles have a greater range and filling the hydrogen tank only takes a few minutes, whereas charging an high voltage battery in pure electric drives takes a comparatively long time. Fuel cells and the complexity of the fuel system make these particular vehicles very expensive. Currently, the necessary infrastructure for refueling the vehicles is not available.

Plug-in hybrid Electric drive Fuel cell
Recovery: possible possible possible
Range of coverage: * * * * * * *
CO2 emissions while driving: * * * * * * *
Charging time: * * * * * *
Costs in €: * * * * *

About the author

Florian Freund

Florian Freund

Florian was Head of Connectivity Solutions at ZF Aftermarket until 2022. His position with the #zfexperts:

“Driving the progress of electric mobility isn´t just my job, it´s my passion.”