Mr. Thomas Kleckers, Product and Application Manager - Force Transducers, HBK
Electric cars play an important role in the decarbonization strategy of many countries. The technology has been improved in the last years, but besides the range of the car, the time required to charge an electric vehicle is also important as shorter charge stops would make them much more attractive to a wider audience.
A shorter time with the same capacity entails operating with higher currents. Current, temperature and number of cycles are the most important factors that influence capacity fading, meaning the decrease of the capacity of a lithium-ion battery.
Traditionally, battery tests are performed by measuring voltage and current. A more innovative method is to measure the force of a lithium-ion pack while charging or discharging processes in a fixed position. Using a suitable load cell, the test can be performed at various temperatures, and long-term tests are possible as well.
The requirements the force transducer must meet are given by the nature of the testing procedure: The long duration requires a low drift, and possible harsh environments make a hermetically sealed load cell necessary. Recent load cells are extremely accurate sensors, but as with every measurement, a certain measurement uncertainty occurs with a battery test as well.
This lecture will discuss the most important technical aspects for choosing a suitable load cell for a “punch cell test”, and you will also learn how to do an easy calculation to get a good estimation of the measurement uncertainty.