On Improving Battery State of Charge Estimation Using Bulk Force Measurements

Lithium-ion (Li-ion) batteries undergo physical deformation as their state-of-charge (SOC) changes. The physical deformation causes changes in the pressure (equivalently, force) applied at the end-plates of a constrained battery pack or module. This paper proposes the fusion of bulk force and battery voltage measurements to estimate the SOC in Li-ion battery packs. In this paper, using discrete Linear Quadratic Estimators (dLQEs), the advantage of using force measurements in addition to voltage measurement to improve SOC estimates is quantitatively studied through simulations. It is observed that including force measurements can decrease the mean and standard deviation of SOC estimation error by 50% in some SOC intervals.