An electronic device comprising: an interface for receiving a battery comprising a battery module for supplying power to the electronic device; and a power management module coupled to the interface for receiving the battery and configured to: measure an electromagnetic radiation spectrum and/or a voltage response of the battery due to current flow in the battery module; compare the measured electromagnetic radiation spectrum and/or voltage response of the battery to at least one of a plurality of reference electromagnetic radiation spectrums and/or voltage responses respectively, each of the reference electromagnetic radiation spectrums and/or voltage responses corresponding with a different relative condition, the relative condition reflecting a condition of the battery module that is relative to an initial condition of the battery module; determine a relative condition of the battery by comparing the measured electromagnetic radiation spectrum and/or voltage response with one of the plurality of reference electromagnetic radiation spectrums and/or voltage responses respectively; and store, in a memory store (108, 254), data identifying the relative condition of the battery, wherein the power management module is configured to: repeat measuring the electromagnetic radiation spectrum and/or the voltage response, comparing the electromagnetic radiation spectrum and/or the voltage response, and determining the relative condition of the battery at a second time such that a second relative condition of the battery is determined; compare the second relative condition of the battery with the relative condition of the battery previously stored in the memory store (108, 254); determine a rate of change between the second relative condition of the battery and the relative condition of the battery previously stored in the memory store (108, 254); and determine if the rate of change exceeds a threshold tolerance level. an interface for receiving a battery comprising a battery module for supplying power to the electronic device; and a power management module coupled to the interface for receiving the battery and configured to: measure an electromagnetic radiation spectrum and/or a voltage response of the battery due to current flow in the battery module; compare the measured electromagnetic radiation spectrum and/or voltage response of the battery to at least one of a plurality of reference electromagnetic radiation spectrums and/or voltage responses respectively, each of the reference electromagnetic radiation spectrums and/or voltage responses corresponding with a different relative condition, the relative condition reflecting a condition of the battery module that is relative to an initial condition of the battery module; determine a relative condition of the battery by comparing the measured electromagnetic radiation spectrum and/or voltage response with one of the plurality of reference electromagnetic radiation spectrums and/or voltage responses respectively; and measure an electromagnetic radiation spectrum and/or a voltage response of the battery due to current flow in the battery module; compare the measured electromagnetic radiation spectrum and/or voltage response of the battery to at least one of a plurality of reference electromagnetic radiation spectrums and/or voltage responses respectively, each of the reference electromagnetic radiation spectrums and/or voltage responses corresponding with a different relative condition, the relative condition reflecting a condition of the battery module that is relative to an initial condition of the battery module; determine a relative condition of the battery by comparing the measured electromagnetic radiation spectrum and/or voltage response with one of the plurality of reference electromagnetic radiation spectrums and/or voltage responses respectively; and store, in a memory store (108, 254), data identifying the relative condition of the battery, wherein the power management module is configured to: repeat measuring the electromagnetic radiation spectrum and/or the voltage response, comparing the electromagnetic radiation spectrum and/or the voltage response, and determining the relative condition of the battery at a second time such that a second relative condition of the battery is determined; compare the second relative condition of the battery with the relative condition of the battery previously stored in the memory store (108, 254); determine a rate of change between the second relative condition of the battery and the relative condition of the battery previously stored in the memory store (108, 254); and determine if the rate of change exceeds a threshold tolerance level. repeat measuring the electromagnetic radiation spectrum and/or the voltage response, comparing the electromagnetic radiation spectrum and/or the voltage response, and determining the relative condition of the battery at a second time such that a second relative condition of the battery is determined; compare the second relative condition of the battery with the relative condition of the battery previously stored in the memory store (108, 254); determine a rate of change between the second relative condition of the battery and the relative condition of the battery previously stored in the memory store (108, 254); and determine if the rate of change exceeds a threshold tolerance level.