Characteristics of Open Circuit Voltage Relaxation in Lithium-Ion Batteries for the Purpose of State of Charge and State of Health Analysis

Open circuit voltage relaxation to a steady state value occurs, and is measured, at the terminals of lithium-ion battery when current stops flowing. It interest for use in determining charge health. As can take several hours, representative model curve fitting necessary practical usage. Previous studies investigate four characteristics: relationship between magnitude charge; length required; complexity estimation; health evaluation. However, previous have inconsistent methodology or only one type cell, making comparison generalization difficult. To address this, we conducted 3 h 24 experiments over range states on three different lithium ion chemistries (nickel cobalt aluminum NCA; nickel manganese NMC532; iron phosphate LFP) fitted them with new equivalent model. was found that period sufficient NMC LFP investigations. Voltage NCA cell continued evolve past h. shown shape changes as function charge, accuracy estimating explored. Strategically choosing assessment be optimized accentuate this differs by chemistry. This suggested technique experimental findings paired degradation determine assessing