Characterisation of cells: DCIR and intensive cycling

Ensure the reliability of the cells

At SIG Energy Technology, the quality and performance of Lithium-Ion cells are our priority and our commitment to excellence. In-depth testing is conducted in our laboratories to understand the behavior of each cell and to develop the specifications imposed on manufacturers, particularly through the measurement of internal resistance and intensive cycling.

Measurement of internal resistance

DCIR is measured upon receipt of the cells, then throughout their calendar aging and during cycling. Conducted at different SoC values, this measurement allows verification that the internal resistance remains within the tolerances defined by the manufacturer. It provides monitoring of performance stability, facilitates defect detection, and feeds into our aging prediction models. When combined with cycling, it becomes a precise indicator of the internal evolution of the cells.

Long-term/intensive cycling

In addition, comprehensive cycleability assessments are conducted on our test benches, with repeated charge-discharge cycles under more intensive conditions than those specified in the technical data sheets or real applications.

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A few years ago, the cells displayed an average of 80% State of Health (SoH) after about 2000 cycles. Today, advancements in technology allow for reaching an average of 80% SoH after 4000 cycles, illustrating a significant progress in cell lifespan.

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In this context, we expect at a minimum that the results obtained conform to the performance claimed by the manufacturer. However, only the cells whose performance exceeds the values in the technical data sheet under our intensive testing conditions are selected. Depending on the performance of the cell, a test can last from 1 month to over 2 years. These tests allow observation of the cell's ability to maintain its performance over time and to detect any potential early degradations.

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During these cycling phases, DCIR measurements are taken every 100 cycles, providing a comprehensive view of the degradation evolution and the cell's lifespan. These analyses allow for refining the parameters of the BMS to accurately calculate SoH and SoC.

‍An advanced testing database

Thanks to these procedures, SIG Energy Technology ensures a thorough understanding of each cell. The combination of DCIR measurements and intensive cycling provides complete visibility into the performance and reliability of the products, enabling integrators to design optimized batteries for their applications.