Changing the climate in our cars

A hot topic for the future - raising potentials through clever thermal management

Cooling was once just a side issue for combustion engines. Either air or liquid cooling agents were used to prevent the system from overheating, with the waste heat created “free of charge” as a helpful by-product for heating the cabin at cold times of year. What about air conditioning? That was reserved for premium-class vehicles. At least that was the state of the art just a few decades ago. And today? - as we all know, every sub-compact car is fitted with an automatically controlled air conditioning system.

Keeping the entire powertrain at the right temperature

Vehicles operating at optimal temperatures achieve their top performance more quickly, consume less fuel, and produce fewer emissions! Sounds good? It is. The engineers at MAHLE quickly recognized the potential of precise thermal management in the powertrain and optimized the coolant circuits.

That’s because a reduced engine mass and less coolant mean the operating temperature is reached more quickly, and it’s only at operating temperature that a combustion engine works at its best, consumes as little fuel as possible, and releases the fewest possible emissions.

And that’s not all. Not only is waste heat now drawn off and used for heating, it also warms the transmission oil. This effectively reduces internal frictional loss from cold, viscous oil. And when the transmission is already connected to the coolant circuit via a heat exchanger, the coolant also serves to bring down the elevated temperatures that occur under high loads.

Taking thermostats to the next level

A “normal” thermostat can only react to the coolant temperature. This means that, when the temperature increases (when overtaking or climbing a hill, for example), it always takes a little while for the thermostat to trigger an adjustment in the coolant circuit to suit the new driving situation.

So, how can the response time be reduced? By using control components that can be actively actuated, such as map-controlled thermostats. These control components use not only the heat from the coolant but also a small heating element in the thermostat to adjust the cooling circuit. As soon as its sensors and built-in engine operating map allow the control unit to identify that more heat will be generated in the system by increasing the engine load, it triggers auxiliary heating in the thermostat. This causes the expansion element to react and the thermostat to change its settings. On the basis of stored information (engine operating map, operating conditions, and sensor values), a map-controlled thermostat is therefore able to respond before an increase in temperature occurs. This means that very accurate, instantaneous temperature control can be achieved.

All information about thermostats (incl. video) you can find >> HERE

MAHLE’s modern thermal management paves the way for e-mobility

Electric vehicles need traction motors, power electronics, batteries, and charging electronics. Their temperature also needs to be controlled. However, each of these components has its own ideal temperature as well as individual limits for minimum and maximum temperatures. With hundreds or even thousands of battery cells, batteries are particularly tricky. They only have a high capacity and long service life when their temperature is optimally controlled. Internal resistors cause them to heat up as soon as there is a flow of current, that is to say, when giving out power, during regeneration (energy recovery when braking), and when charging.

The great challenge for thermal management is to keep precisely within the ideal temperature ranges. This means that the air conditioning system—consisting of air conditioning compressor, condenser, expansion valve, and evaporator—is more than simply a pleasant luxury in the summer. It’s essential to the operation of the vehicle and the optimum functioning of all components.

For this reason, an additional heat exchanger—known as a chiller—is connected to the air conditioning circuit. This cools the low-temperature circuits in electric drive systems. In the past, maintenance of air conditioning systems was often only carried out in the event of a systems failure, if at all. But A/C servicing is an absolute must for the workshop professional when it comes to electric vehicle maintenance.

Special challenges for the air conditioning system—and a cool solution from MAHLE

There are three particularly important tasks you must carry out in an A/C service: cleaning the condenser, running a functional test, and checking the level of refrigerant in the system. Having the right amount of refrigerant isn’t just critical for reliable operation, it also makes sure the compressor oil (e.g. PAG, POG) is equally distributed.

The only way to check the fill level is by using an air conditioning service unit. This involves extracting the refrigerant present in the system and weighing it in the A/C service unit. After testing the vehicle’s system for leaktightness, you must then return the cleaned refrigerant from the A/C service unit according to manufacturer's specifications to the air conditioning system along with any extra amount required.

In electric vehicles, cooling and heating processes take energy from the battery, which impacts the vehicle’s cruising range. How can this challenge be overcome? MAHLE has implemented some great ideas. After all, heating doesn’t have to be done with electric heaters: the air conditioning system can simply be made to run in reverse. This way, it works like a heat pump from the outside to the inside.

We’re aware that managing the heat flows arising within electric, hybrid, and fuel cell vehicles has a major impact on cruising range and comfort, and thus on the acceptance of e-mobility. MAHLE’s approach focuses on integrated systems and product solutions—in service and diagnostics too.

Conventionally powered vehicles will still be found on the roads, and therefore presumably in your workshop too, for many years to come. But the sharp rise in the number of new electric vehicles being registered suggests that you’d be wise to prepare for new technologies if your business is going to be fit for the future. We support you!

The use of MAHLE’s thermal management systems in electric vehicles therefore results in:

>> up to 20% greater cruising range or

>> a reduction in battery capacity of up to 20% with the same cruising range

MAHLE Aftermarket—the home of thermal management

From 2020, you’ll be able to get the entire thermal management product range in OEM quality, all from MAHLE Aftermarket: thermostats, switches, sensors, air conditioning compressors, radiators, heaters, heat exchangers, condensers, and water pumps.

MAHLE Aftermarket is here to support you with the very best products and complete systems in original quality, state-of-the-art workshop equipment, and a wide range of training programs—guiding you expertly into the future.


We regularly provide technical tips relating to the powertrain, thermal management, and mechatronics in automobiles.


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