Abstract: A battery (1) has identification means for enabling an apparatus e.g. a radio telephone or a battery charger, connected to the battery to determine a plurality of battery parameters e.g. temperature and battery capacity using a single measurement, so that, for example, a battery charger can adopt the correct charging regime for the battery type. The identification means is provided by a constant current source (I) and one or more solid state components (D1-D3) having p-n junctions e.g. diodes or transistors coupled in series or in parallel. As the threshold voltage (V.sub.D) of p-n junctions vary with temperature, and the number of components can be made to vary with battery type, by measuring the total voltage drop (Vo) across series connected components or current through parallel connected components which will vary with temperature and the number of components, a single signal can provide information on more than one battery parameter.