Traceability of low impedances

Purpose and goal

The aim of the project was to establish traceability for impedance measurements at the low impedance levels that are typical of Li-ion type battery cells used in vehicles, among other things. Typical impedance levels are 1 milliohm or lower. This is to be able to ensure the quality of various impedance-based diagnostic methods for state of health and state of charge in battery cells. The project was partly successful. We have established traceability for impedance down to 1 milliohm at frequencies from 10 hertz to 100 kilohertz. New measurement methods have been useful in other projects.

Expected results and effects

Through the project, we have expanded the impedance range at Riksmätplatsen down to 1 mOhm in the frequency band 10 Hz-100 kHz, an area that is relevant for Li-ion batteries. We have also strengthened our expertise in the battery area through cooperation with the battery lab at RISE. The results lay the foundation for developing new calibration services for battery measuring instruments and improved diagnostic methods for battery cells at Riksmätplatsen.

Planned approach and implementation

The project started well and had realistic goals. Unfortunately, the group was understaffed for a period due to staff leaving and periods of sick leave. This meant that the project was given lower priority and was delayed. We tried to solve this by engaging two people in another department, but these two also left RISE before they had completed the work. The result was that the project´s goals were only partially met. Despite this, we believe that what was done in the project was still successful. In retrospect, we should have acted faster when the shortage of staff became apparent.