Lithium-ion cell fault detection by single-point impedance diagnostic and degradation mechanism validation for series-wired batteries cycled at 0°C

Abstract

The utility of a single-point impedance-based technique to monitor the state-of-health of a pack of four 18650 lithium-ion cells wired in series (4S) was demonstrated in a previous publication. This work broadens the applicability of the single-point monitoring technique to identify temperature induced faults within 4S packs at 0°C by two distinct discharge cut-off thresholds: individual cell cut-off and pack voltage cut-off. The results show how the single-point technique applied to a 4S pack can identify cell faults induced by low temperature degradation when plotted on a unique state-of-health map. Cell degradation is validated through an extensive incremental capacity technique to quantify capacity loss due to low temperature cycling and investigate the underpinnings of cell failure.