Thermoelectrics—A new type of battery cooling and heating
Thermoelectric battery temperature control using a thermoelectric heat pump integrated in a battery plate presents an interesting alternative to classic temperature control methods linked to the air conditioning system and with separate heating components. MAHLE’s Corporate Advanced Engineering developed this disruptive technology over the last 3 years and has now released it for series development.
A lithium-ion battery must be kept within a temperature range between about 0°C and 45°C during operation in order to fulfill the required long service life. At high external temperatures, the engine cooling circuit reaches its limits, which is why the waste heat from the battery is now dissipated via the air conditioning circuit. In turn, a water heater or film heater is needed to heat the battery in winter. Recently, thermoelectric heat pumps have become the focus of battery temperature control. The advantages include intrinsic heating functionality and systemic independence from the air conditioning circuit, lower complexity, and reduced package constraint.
The thermoelectric heat pump makes use of the Peltier effect. Depending on the direction of the electric current applied to it, heat is pumped from one side of the thermoelectric module (TEM) to the opposite side, so that the TEMs on one side heat up, while those on the other side cool down. The thermoelectric battery plate (TE battery plate) consists of several TEMs connected to the battery cells via a heat spreader on one side, and to a fluid plate with a low-temperature coolant circuit on the other. With electronics for controlling the TE heat pump, the lithium-ion battery is cooled and heated directly using electrical energy.
The essential components of the TE battery plate are the TEMs, which are available worldwide from various manufacturers. While the base materials are comparable, their internal designs vary greatly—and that affects their durability. In order to meet typical automotive specifications, therefore, MAHLE has built a TEM test facility. It allows the TE parameters of the various modules to be characterized and tested, while extensive series of tests can be performed on TEMs from various manufacturers, including under different climatic conditions. Thermoelectrics, due to their independence from the air conditioning circuit and their integrated heating functionality, offer great advantages in comparison with the classic battery temperature control using air, refrigerant, and coolant, especially for mild hybrids and electric vehicles. In order to make use of this technology, in-depth understanding is required not only of thermodynamics but also of the thermoelectric modules, their controls, durability, and integration in the heat exchanger. This interaction is the only way to present an attractive product in terms of cost, weight, and package constraint.
- Thermoelectric battery cooling makes use of what is known as the Peltier effect.
- The advantages include intrinsic heating functionality and systemic independence from the air conditioning circuit, lower complexity, and reduced package constraint.