  Battery energy storage systems (BESSs) provide many benefits to the
electricity grid, including stability, backup power, and flexibility in
introducing more clean energy sources. As BESS penetration grows, knowledge of
the uncertainty in the battery's state of charge (SOC) estimate is crucial for
planning optimal BESS power injection trajectories. This paper proposes a
framework for quantifying SOC estimation uncertainty based on battery rest
periods. An uncertainty analysis is presented for a BESS participating in the
frequency regulation market.
