Test Method for Thermal Characterization of Li-Ion Cells and Verification of Cooling Concepts

Abstract

Temperature gradients, thermal cycling and temperatures outside the optimal operation range can have a significant influence on the reliability and lifetime of Li-ion battery cells. Therefore, it is essential for the developer of large-scale battery systems to know the thermal characteristics, such as heat source location, heat capacity and thermal conductivity, of a single cell in order to design appropriate cooling measures. This paper describes an advanced test facility, which allows not only an estimation of the thermal properties of a battery cell, but also the verification of proposed cooling strategies in operation. To do this, an active measuring unit consisting of a temperature and heat flux density sensor and a Peltier element was developed. These temperature/heat flux sensing (THFS) units are uniformly arranged around a battery cell with a spatial resolution of 25 mm. Consequently, the temperature or heat flux density can be controlled individually, thus forming regions with constant temperature (cooling) or zero heat flux (insulation). This test setup covers the whole development loop from thermal characterization to the design and verification of the proposed cooling strategy.