A method for abnormality detection in an energy unit includes passively detecting an abnormality in an energy unit by detecting electromagnetic radiation generated by the abnormality, the energy unit comprising at least one of an electrical energy unit and an electrochemical energy unit. A method for detecting an abnormality in an energy unit includes (a) applying a signal to the energy unit, (b) performing a plurality of measurements, at a respective plurality of different locations within the energy unit, of a response of the energy unit to the signal, and (c) processing the plurality of measurements to identify the abnormality.