A method and system for determining the state-of-health of a nickel-metal hydride battery connected to a load comprises: detecting at least one of a real and imaginary part of an impedance of the battery at each of a first set of selected frequencies, the first set of selected frequencies including at least one frequency, and determining the state-of-health of the battery from a fuzzy system trained in a relationship between each impedance and the state-of-health, wherein the state-of-health is a function of the battery's ability to deliver power required by the load and the battery's capacity to meet load requirements.