March 23, 2023

PHEV Essentials: How they Work

Plug-in hybrid electric vehicles (PHEVs) combine the efficiency of a traditional combustion car with the versatility of an electric car.

Plug-in hybrids combine the battery pack of an electric car with a conventional car that has a gasoline engine, usually for better acceleration. These cars are useful for those who want to minimize their use of gasoline and also want to utilize the availability of electricity.

Perhaps you don’t want to go for a fully electric vehicle? PHEV will be your ideal alternative.

How do plug-in hybrid electric cars work? 

Plug-in hybrid electric cars are like other hybrid cars. They use a combination of an electric motor and a car’s engine to accelerate. The electric motor is powered by a battery pack that can be charged from an external source of electricity.

The car’s engine is powered by a fuel source like gasoline. The electricity that comes from the electric car’s battery is sent through a special connector called a charging port. This allows the car’s battery to be recharged from an electric source like a standard wall socket. 

The car’s engine will not operate unless the car is connected to a source of gasoline. Most plug-in hybrid electric cars can be driven in electric-only mode or electric-hybrid mode.

In electric-only mode, the electric motor helps the car accelerate. In electric-hybrid mode, the car’s engine is also used to help accelerate. There are different types of plug-in hybrids.

Key components of Plug-in hybrid electric vehicle

Here are the key components that facilitate the working mechanism of a PHEV vehicle.

Auxiliary battery

This battery provides electrical energy that is used for starting the car. It is just like the batteries used in other vehicles. The charging process is similar to that of a regular battery.

Traction battery pack

The traction battery is used to power the vehicle’s electric motor as well as the electric motor that is used to recharge the traction battery. The size and capacity of the traction battery depend on the vehicle’s design.

Electric motor

This component is only used while driving in electric-only mode. It is connected to a gearbox that mechanically connects it with the transmission.

Battery charger

This component provides electrical energy that charges up the traction battery. It also has a cooling fan for extra protection against overheating. The charging process can take up to four hours depending on whether or not you have a fast-charging port at home or work. The charging voltage will depend on how fast you charge your car. 

The charging process can be completed overnight in most cases, but this varies depending on whether you have a standard wall socket, a high-powered socket, or an unusual socket (for example, an SAE J1772 “plug-in” socket).

DC/DC converter

This component is used to convert the DC charge from the traction battery into a DC current that can be used to power the vehicle. Some DC/DC converters have multiple outputs that allow you to use one side of the converter as a fast-charge port while using the other side as a normal charging port.

Electric generator

PHEVs can generate electricity by themselves-you don’t have to always charge the battery on the wall socket. This is where the importance of an electric generator comes in. It generates electricity from the rotating wheels and regenerative braking. The generator then transfers this electricity to the tractive battery pack for storage.

Battery management system

This is a software-controlled digital controller that manages the charging and discharging of the battery pack(s).

It helps to maintain optimum performance during operation and to protect it against damage during charging, discharging, and other conditions.

The battery management system monitors the state of charge of the battery pack(s) and controls the charging process accordingly. This can include controlling when charging begins or stops, controlling how fast or slow charging occurs, controlling what current is drawn from the battery pack(s), determining when to turn off charging, etc.

Transmission system

Transfers the mechanical energy from the engine and the traction motor to the vehicle’s drive wheels. It also controls and regulates the energy/torque transfer to the wheels.

Charging port

The charging port is the connection point between the battery pack(s) and the charging system.

It is where the battery pack(s) are connected to the charging system for recharging.

Cooling system

A cooling system is used to keep the battery pack(s) at an optimal temperature for optimum battery performance and safety.

The engine and the traction motors also have cooling or thermal systems which aid in temperature management for optimum performance.

Internal combustion engine

The internal combustion engine (ICE) is the primary source of mechanical energy for the vehicle.

It is usually a reciprocating four-stroke engine. The ICE is the most complex component of a vehicle and is designed to operate within a wide range of speeds and temperatures.

Exhaust pipe(s)

The exhaust pipe(s) connects the engine to the tailpipe/exhaust system, which is connected to a muffler. The muffler can be located under or behind the vehicle.

It can also be located in front of or beside it depending on vehicle design. The muffler is designed to reduce noise levels emitted by vehicle systems when they are operating.

Can a plug-in hybrid run on electricity only?

A unique feature that comes with PHEV and not in conventional hybrid vehicles is the ability to run on electricity only. However, I will only run for a limited range depending on the battery’s capacity. 

Perhaps this is one of the reasons why PHEVs are perfect for daily city driving.

What happens if you don’t charge a plug-in hybrid battery?

This is a very common question and the answer is simple.

If you do not charge the battery, then it would be useless for you. If you leave it uncharged for a long time, then it would become unusable to run your engine because there is no power left in the batteries. So, if you don’t charge your plug-in hybrid’s batteries, then it will be useless for your driving needs.

What are the pros of plug-in hybrid cars?

Plug-in hybrids have a number of advantages over conventional hybrids, including:

1) No range anxiety: The greatest advantage of PHEVs over conventional hybrids is that they don’t have range anxiety (the fear of running out of electricity) like conventional hybrids do when they are used only as electric vehicles.

2) More efficient than conventional hybrids: Plug-in hybrids will typically be more efficient than most conventional hybrids when used in the electric mode because they use a smaller battery pack and do not require the engine to be running for the vehicle to operate (since the vehicle is being driven in electric mode, the engine does not need to run).

3) More efficient than conventional hybrids when used in hybrid mode: Plug-in hybrids will typically be more efficient than most conventional hybrids when used in the hybrid mode because they use a smaller battery pack and do not require the engine to be running for the vehicle to operate (since the vehicle is being driven in hybrid mode, the engine does not need to run). This leads us to our next point…

4) Higher efficiency than conventional hybrids: Plug-in hybrids are more efficient than most conventional hybrids because they do not require their engines to run as often as conventional hybrids, thus resulting in lower fuel consumption.

5) Less polluting than conventionals: Plug-in hybrids can be less polluting than most traditional combustion engines because they have no tailpipe emissions.

What are the disadvantages of PHEVs?

1) Additional battery life required: While the range of PHEVs is typically longer than that of conventional hybrids, the rechargeable battery pack in these vehicles is larger and heavier than that used in conventional hybrids.

2) More expensive: PHEVs cost more than most conventional hybrids on average since they are more efficient and require a larger battery pack.

3) Less available to consumers: Since plug-in hybrid vehicles are still relatively new, they are not as common as conventional hybrids. As a result, they are not as popular or widely available as most other hybrid cars today.

4) Lower fuel economy: Due to their higher efficiency, plug-in hybrids do not have the same fuel economy as most traditional combustion engines.

5) Higher operating costs: Plug-in hybrid vehicles have higher operating costs compared to traditional combustion engine vehicles due to the additional energy needed for charging the vehicle’s battery pack (or recharging station).

6) More expensive to own over time: Since PHEVs require a larger battery pack than conventional hybrids, they will have higher average ownership costs over time.

7) More expensive to maintain: Due to their greater reliance on electricity, PHEVs are more costly to maintain than most conventional hybrids.


We cannot dispute the fact that PHEVs are becoming popular. If you are planning to buy one, you are on the right track. Their higher fuel economy and lower operating costs are enviable. In addition, they have the added benefit of being able to recharge their batteries using electricity from your home or workplace.

As a result, PHEVs are becoming more common and will continue to be so as more people discover their advantages.


Cleophas is a tech enthusiast and also an automotive engineer. Is specialize in electric vehicles and bikes.

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