Abstract: An energy management system includes an energy input sensor, an energy output sensor and a system controller. The energy input sensor is configured to generate at least one energy input signal indicating an energy flow to an energy storage medium of an energy storage device. The energy output sensor is configured to generate at least one energy output signal indicating an energy flow from the energy storage medium. The system controller is configured to estimate a charge level of the energy storage medium based on an initial charge level of the energy storage medium and a change in the charge level of the energy storage medium, which is based on the at least one energy input signal and the at least one energy output signal.