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  • Marco Bonifaccino

Thermal Management in Electric and Hybrid Vehicles

Updated: Jun 15, 2022

The following information will give you an overview of the respective electric and hybrid technologies. From the basics and system properties, to solutions for thermal management and special features on the subject of maintenance, repair, and towing. You will also find important information about the qualifications required for the work in question.

Important safety information

The following technical information and practical tips have been compiled by AC diagnosis, source HELLA TECH WORLD, in order to provide professional support to vehicle workshops in their day-to-day work. The information provided on this blog is intended for use by suitably qualified personnel only.



More than 2 million electric cars and plug-in hybrids were sold worldwide for the first time in 2018. With 2.1 million vehicles sold, their market share has risen to 2.4 percent of all new registrations – and the trend continues to rise. (Centre of Automotive Management). In Norway, for example, the market share is already at 50%!

According to the International Energy Agency (IEA), the growth of electric and hybrid mobility is driven primarily by government programs such as sales bonuses, local driving bans for cars with internal combustion engines, or targets for clean air. The authority considers e-vehicles to be one of several current drive technologies that can be used to achieve the long-term sustainability goals of reducing emissions. According to a study by management consultants PricewaterhouseCoopers,

every third new car registered in Europe in 2030 could be an electric car.

Therefore, it is no longer a question whether vehicles with electric, hybrid or hydrogen technologies will really prevail. They will soon become part of everyday life on our streets.

These vehicles will also have to be serviced and repaired, and the subject of thermal management will become increasingly complex.

The temperature control of the battery and power electronics plays just as important a role as the heating and cooling of the vehicle interior.

Air-conditioning components are also required for these types of drives – and their importance is increasing, since the air-conditioning system often has a direct or indirect influence on the cooling of the batteries and electronics. Air-conditioning maintenance will therefore play an even more important role in the future.


The term "hybrid" as such means a mix or a combination. With respect to vehicle engineering, this term means that an internal combustion engine with standard drive technology has been combined with elements of an electric vehicle in one vehicle.

Hybrid technology has three stages of complexity: from micro-hybrid to mild-hybrid up to full-hybrid technology. Despite technical differences, one thing all the technologies have in common is that the battery used is charged by recovering braking energy.


are usually equipped with a standard internal combustion engine, a start/stop automatic system, and a braking energy recovery (recuperation) system.


in contrast also have an additional (small) electric motor and a more powerful battery. The electrical auxiliary drive is only used as assistance when starting and for greater power delivery when overtaking, a concept known as "boosting".


can not only "boost"; they can also drive purely on electricity. To this end, they are fully equipped with an electric drive train. However, this requires a much more powerful battery than a mild hybrid.


allow the batteries to be charged overnight, for example. The positive side effect of this vehicle type is that, at the same time, the passenger compartment can be brought to a desired temperature before the vehicle is driven. This means that the vehicle is immediately ready for use the following morning. The plug-in hybrid is a form of full hybrid.


By definition, an electric vehicle is a motor vehicle driven by an electric motor. The electrical energy required for its movement is obtained from a drive battery (accumulator), i.e. not from a fuel cell or a range extender. Since the electric car itself does not emit any relevant pollutants during operation, it is classified as an emission-free vehicle.

In electric vehicles, the wheels are driven by electric motors. Electrical energy is stored in accumulators in the form of one or more drive or supply batteries.

The electronically controlled electric motors can deliver their maximum torque even at standstill. Unlike internal combustion engines, they usually do not require a manual transmission and can accelerate strongly even at low speeds. Electric motors are quieter than petrol or diesel engines, almost vibration-free and emit no harmful exhaust emissions. Their efficiency of more than 90% is very high.

The relatively high weight of the accumulators is offset by the weight saving due to the elimination of the various components (engine, transmission, tank) of the combustion engine. Electric vehicles are therefore usually heavier than corresponding vehicles with combustion engines. The capacity of the battery(s) has a great influence on the vehicle weight and the price.

In the past, electric vehicles had short ranges with one battery charge. Recently, however, the number of electric cars that can reach distances of several hundred kilometres is increasing, for example: Tesla Model S, VW e-Golf, Smart electric drive, Nissan Leaf, Renault ZOE, BMW i3.

In order to further increase the range of electric vehicles, additional devices (usually in the form of an internal combustion engine) are sometimes used to generate electricity. This is referred to as the "range extender".


To be able to operate an electric vehicle with a particularly high level of efficiency, it is necessary to maintain an optimal temperature range for the electric motor, the power electronics and the battery.

This requires a sophisticated thermal management system:

- Refrigerant-based system (or direct battery cooling)