Studies for an optimal balancing system for Li ion batteries based on state of health assessment

Li-ion batteries are the most popular energy storage choice for a wide range of applications, especially electric and hybrid electric vehicles, because of their superior characteristics in comparison to the other energy storage technologies. It has been observed that there are significant differences regarding parameters within the same batch of batteries manufactured and that mainly due to technological barriers which cannot be over passed without expensive efforts. To avoid additional stress and battery premature destruction it is necessary to develop a new approach for balancing between cells during electrical or hybrid-electrical vehicles driving cycles. This paper presents a thorough behavioral study of Li-ion cells during the ageing phenomenon, as well as the possibility of employing electrochemical impedance spectroscopy for assessing the batteries state-of-health. The latter can be used to further develop a coherent algorithm to be employed in a smart adaptive balancing system.