A battery system, comprising: - a battery comprising one or more battery cells and configured to couple to an electrical system; - one or more sensors configured to measure a plurality of battery parameter sets during operation of the battery, wherein each battery parameter set of the plurality of battery parameter sets comprises a terminal voltage and a terminal current; and - a battery control module configured to electrically couple to the battery, wherein the battery control module is configured to: - monitor the plurality of battery parameter sets of the battery; - recursively calculate a first capacity estimation of the battery using two linear regression models based on at least an equivalent circuit model, at least one of the monitored battery parameter sets, and a Kalman filter, which is based at least in part on a first relationship between the terminal voltage and the terminal current of the battery with an open circuit voltage of the battery, an ohmic resistance of the battery, and a charge transfer resistance of the battery; and - control charging of the battery, discharging of the battery, or both based at least in part on the capacity of the battery, wherein a first linear regression model of the two linear regression models is configured to calculate a state of charge estimation of the battery, and wherein a second linear regression model of the two linear regression models is configured to calculate the first capacity estimation based at least in part on the state of charge estimation, wherein the state of charge estimation of the first linear regression model is calculated via an open circuit voltage to state of charge look-up table based on the open circuit voltage of the battery estimated using the Kalman filter, and wherein in case the battery control module determines that the state of charge estimation calculated by the first linear regression model is usable as an input for the subsequent second linear regression model, the battery control module is configured to calculate a maximum state of charge change based on minimum and maximum state of charge values and to calculate the first capacity estimation by executing the Kalman filter based on a relationship between the first capacity estimation of the battery with the state of charge change and an accumulative ampere-hour throughput of the battery during the state of charge change. - a battery comprising one or more battery cells and configured to couple to an electrical system; - one or more sensors configured to measure a plurality of battery parameter sets during operation of the battery, wherein each battery parameter set of the plurality of battery parameter sets comprises a terminal voltage and a terminal current; and - a battery control module configured to electrically couple to the battery, wherein the battery control module is configured to: - monitor the plurality of battery parameter sets of the battery; - recursively calculate a first capacity estimation of the battery using two linear regression models based on at least an equivalent circuit model, at least one of the monitored battery parameter sets, and a Kalman filter, which is based at least in part on a first relationship between the terminal voltage and the terminal current of the battery with an open circuit voltage of the battery, an ohmic resistance of the battery, and a charge transfer resistance of the battery; and - control charging of the battery, discharging of the battery, or both based at least in part on the capacity of the battery, - monitor the plurality of battery parameter sets of the battery; - recursively calculate a first capacity estimation of the battery using two linear regression models based on at least an equivalent circuit model, at least one of the monitored battery parameter sets, and a Kalman filter, which is based at least in part on a first relationship between the terminal voltage and the terminal current of the battery with an open circuit voltage of the battery, an ohmic resistance of the battery, and a charge transfer resistance of the battery; and - control charging of the battery, discharging of the battery, or both based at least in part on the capacity of the battery, wherein a first linear regression model of the two linear regression models is configured to calculate a state of charge estimation of the battery, and wherein a second linear regression model of the two linear regression models is configured to calculate the first capacity estimation based at least in part on the state of charge estimation, wherein the state of charge estimation of the first linear regression model is calculated via an open circuit voltage to state of charge look-up table based on the open circuit voltage of the battery estimated using the Kalman filter, and wherein in case the battery control module determines that the state of charge estimation calculated by the first linear regression model is usable as an input for the subsequent second linear regression model, the battery control module is configured to calculate a maximum state of charge change based on minimum and maximum state of charge values and to calculate the first capacity estimation by executing the Kalman filter based on a relationship between the first capacity estimation of the battery with the state of charge change and an accumulative ampere-hour throughput of the battery during the state of charge change.