Thermal Management Solutions for BEVs

The HVAC system of electric vehicles has multiple functions with regard to heating and cooling processes for passenger comfort and also for optimal conditioning of the battery system and other electric components – direct or indirect. Therefore, the refrigerant cycle is monitored by several temperature and pressure sensors enabling the control unit to regulate the complete system via different valves. Hence, the HVAC system has a major role within the complex vehicle thermal management.

TDK Solution

TDK offers well established robust sensor systems for several applications to monitor the refrigerant cycle.

Suitable Products

 Temperature Sensors Pressure-Temperature Sensors 

Monitoring environmental temperature conditions is important to provide essential information for passenger comfort control and optimal battery thermal conditioning.

TDK Solution

TDK offers well established robust temperature sensor systems, which are designed to track the outside temperature very accurate. These sensors can be integrated in the vehicle bumpers or inside the outside mirror.

Suitable Products

The efficient combination of several heating and cooling applications for passenger cabin comfort is mandatory to reach higher range of electric vehicles. This is based on the fact that all energy for heating and cooling processes come from the vehicle battery only.
Therefore monitoring and controlling the several applications within an optimized thermal management system is the key to provide high driving range in combination with best passenger comfort.

TDK Solution

TDK offers a wide range of well-proven temperature sensor systems, which are designed to track the temperature of cabin inlet air. Additionally TDK offers temperature sensors monitoring applications such as heated steering wheel, heated seats and also other dedicated heated surfaces in electric vehicles. Furthermore TDK has a broad portfolio of PTC heaters for air and liquid PTC heater modules for cabin and battery heating of electric vehicles.

Suitable Products

The navigation software in electric vehicles (EVs) includes speed limits along the route to estimate the car’s driving range. Highways – especially when there is no speed limit – are excluded because the air resistance increases with the square of velocity. To increase the maximum range without limiting the maximum speed, air resistances have to be reduced. This can be done by mechanically closing radiator openings, folding mirrors, or extending spoilers.

TDK Solution

The Arm® Cortex®-M3 based embedded motor-controller family HVC 4xxxF from TDK drives stepper, BDC and BLDC motors in e.g. radiator grill shutters, and in fold mirror or spoiler applications. It allows complex motor control algorithms (e.g. SVM for PMS motors), six-step commutation with sensor feedback or sensor-less control, as well as various stepper algorithms with current limiting and stall detection. The GPIO application interface also enables the integration of sensors for high-precision motor control.

Suitable Products

In order to maximize the driving range of electric vehicles (EVs), car manufacturers are focusing on optimizing energy efficiency and increasing battery capacity. This poses new challenges for the thermal management system of EVs: Battery, charging system, power inverter, motor, and even the passengers themselves have individual and non-compatible ideal operating temperatures.

TDK Solution

Thermal sensors are required at every location to measure local temperatures; thermal valves are required to route and control the cooling/heating fluids. TDK has developed sensor and motor-controller solutions, like temperature sensors, stray-field robust 3D position sensors, or small LIN controlled motor actuators, especially for these tasks.

Suitable Products

 Position Sensors Embedded Motor Controllers

Thermal valves for refrigerant distribution are multiplying in hybrid-electric and electric vehicles as many high-power applications have different thermal needs at different times, e.g. cooling of fast chargers while parking, park heating or cooling, cooling of motor-control inverters and electric motor while driving, or keeping the battery temperature constant during charging and driving.

TDK Solution

TDK has developed position sensors and motor-controllers for thermal valve applications: The HVC 4xyzF controls positioning motors in thermal needle valves, while the HAL 39xy 3D HAL® position-sensors accurately detect rotary and linear movements. The HVCs integrate power-supply, microcontroller, LIN-transceiver, motor driver, and sensor interfaces into one single package. Especially high-voltage and high-current applications in EVs benefit to stray-field immune Hall-effect sensors.

Suitable Products

 Position Sensors Embedded Motor Controllers

The appropriate temperature monitoring of battery coolant is a basic requirement to determine the operating state of the battery and to perform battery operation safely and efficiently. Insufficient temperature monitoring can lead to wear of the system components, reduced service life, or even failure of the components. In a worst-case scenario, major overheating can cause the battery to catch fire.

TDK Solution

The pipe-mounted sensors, so-called ‘clip-on’ sensors, measure the temperature of the coolant. Because the sensors are mounted on the outside of the coolant pipes, no further sealing is required to protect them against the coolant leakage. This allows more flexibility in terms of the design of the piping and installation of the sensor compared with solutions requiring a mounting hole. Sensor dimensions and electrical parameters can be adjusted to customer-specific requirements.

• Clip-on design
• Serviceability
• Fast and reliable mounting and dismounting
• No leakage issue

Suitable Products

High-voltage batteries achieve optimum energy efficiency at precisely defined operating temperatures. Reliable monitoring and control of the battery temperature prevent the battery from overheating, which improves the battery life time and increases safety. To do this, the battery temperature must be measured at multiple points to prevent local overheating. 

TDK Solution

TDK has developed temperature sensors to ensure best thermal contact to the battery surface. With support of ring tongue, made out of different material compatible to the battery surface, an easy attachment is possible. The types of the spring load series are pushed to the battery surface with external spiral spring, flat spring or plastic hook. This smart mounting solution compensate the interface tolerance and ensures excellent thermal contact over lifetime. Furthermore charging time can be reduced by keeping the battery temperature within operating temperatures, which can be achieved by additional heating during cold environmental conditions.

• Ring tongue, spring load and temperature sensor design
• HV strength and humidity resistance
• Smart mounting concept for temperature off set reduction

The PTC SMD limit temperature sensors have been developed for very small dimensions as SMD size 0402, 0603 and 0805. It is a reliable and space-saving solution, which can be used due to reflow soldering for automated production lines.

TDK has developed PTC heaters for air and liquid PTC heater modules for battery heating. It heats up fast the battery and has no risk of burning due to its self-regulating characteristics. Furthermore, the ceramic based PTC heaters do not change their product characteristics over lifetime.

Suitable Products

 Temperature Sensors SMD NTC Sensors SMD PTC SensorsPTC Heaters

Efficient battery management plays a key role in hybrid and electric vehicles (xEVs). The most important task of battery monitoring is always knowing the status of the battery. To maximize the driving range, the charging and de-charging current must be measured precisely and reliably. Especially high-voltage batteries (400 V / 800 V) in xEVs require galvanic isolated current sensing and a very high safety integration.

TDK Solution

TDK has developed a current-sensor solution for battery management in xEVs. The Tunnel Magneto Resistive (TMR) sensing technology allows contactless current sensing with galvanic isolation to the high-voltage battery supply. The coreless system design reduces weight and size of the module system. CUR 423x is designed for the precise current-sensing in safety-relevant applications.

Suitable Products

Electric motors work best at temperatures around 100 °C, at higher temperatures, the motor power drops rapidly. Thus, temperature sensors are used for de-rating of electric motors. Temperature sensors protect also the stator winding from overheating and damaging of the motor insulation. Temperature sensors need to react fast at temperature changes, withstand the challenging mechanical and environmental conditions and offer a sensor mounting concept, which reduces the efforts of integration. 

TDK Solution

TDK temperature sensors offer easy and smart clip and interlocking systems to ensure fast sensor integration. No additional gluing or fixing is required. The temperature sensors are resistant against ATF oil and offer high dielectric strength combined with excellent thermal conductivity at the same time. TDK offers also alternative sensor encapsulation materials like hard or soft sensor housings to simplify the sensor integration for the customer.

• Easy mounting and dismounting
• Robust locking system
• Excellent thermal conductivity
• High dielectric strength
• ATF resistance

Suitable Products

Especially in HV systems, inverters operate under high loading conditions. These high load conditions lead to heating up of the entire systems and to a reduced overall system performance. An optimal inverter operating performance requires temperature control and even active cooling. At the same time, overheating protection of sensitive power electronics is a must to overall longevity of inverter.

TDK Solution

The TDK portfolio comprises NTC temperature sensors with ring tongue series to control the inverter temperature. The sensor attachment ensures good thermal coupling and low temperature offset. Moreover, TDK sensors are validated to operate in HV conditions.

• Easy and flexible mounting
• High dielectric strength 
• Good thermal coupling
• Fast response time
• Compatible to different surfaces

Suitable Products

Vehicle inlet connectors are subject to high temperatures during the charging process. To ensure reliable temperature monitoring and to avoid overheating, the International Electrotechnical Commission stipulates that temperature sensors used in connector systems must meet the minimum requirements of the IEC TS 62196-3 1 DIN standard. For this reason, a reliable measuring accuracy with a narrow temperature tolerance is an essential requirement for temperature sensors.

TDK Solution

The K862 series offer a miniaturized design. The small sensor housings made out of ceramics enable optimal connection of the sensors to the surface of the connector pins ensuring excellent thermal contact and is designed to withstand high dielectric strength up to 4 kV AC. 

• Miniaturized design
• High dielectric strength 
• Excellent thermal conductivity

PTC SMD limit temperature sensors were developed in SMD sizes 0402, 0603 and 0805. It is a reliable and space-saving solution, which can be used for automated production lines.

• Small dimensions
• Fast and reliable response
• Reflow soldering possible

Suitable Products

 Temperature Sensors SMD NTC Sensors SMD PTC Sensors