Application of electrochemical noise analysis to the study of batteries: state-of-charge determination and overcharge detection

For the first time, electrochemical noise has been studied for different types of battery under galvanostatic conditions. First, ENA has been applied successfully to sealed Ni–MH batteries: (i) for low capacities, the noise level gives an estimate of the battery state-of-charge, (ii) for high capacities (up to 93 A h), overcharge detection is achieved simultaneously or prior to other known end-of-charge criteria such as voltage and temperature derivatives. Secondly, ENA has been evaluated for overcharge detection of Ni–Cd or Li-ion batteries: (i) similar results to Ni–MH batteries are obtained for Ni–Cd technology, (ii) for Li-ion batteries, ENA measurements not only allow overcharge detection but also provide an estimate of the gas evolution rate. This technique could be extended to other batteries producing gas during working or overcharging, such as lead–acid batteries.