Capacity estimation for lithium-ion batteries using adaptive filter on affine space

In this paper, we propose a method to estimate the full charge capacity (FCC) of a battery based on an adaptive filter. The FCC is estimated as a ratio of the accumulated charge current to the state of charge (SoC) of the battery, which is estimated by an extended Kalman filter. We consider bias errors on the estimated SoC caused by the error of the typical value of the FCC, which is assumed in the SoC estimation. We also consider the current sensor offset, which causes unboundedness of variables in the FCC estimation. We compose an adaptive filter on an affine space to avoid the unboundedness, which is undesirable for an implementation in embedded systems.