Accurately estimating the battery pack's state-of-charge is crucial for electric vehicles. This study introduces a new way to estimate the state-of-charge of a battery pack by creating a model that considers the differences between individual battery cells. The researchers developed a method that uses two types of filters to identify the battery pack's parameters and predict its state-of-charge in real-time. By testing this method on lithium-ion batteries under different conditions, they found that it can accurately estimate the battery pack's state-of-charge.