A battery pack comprising: a pair of physically separate electrochemical batteries (103, 103'), each battery being an elongate modular unit having a respective pair of electrodes (109, 109') projecting therefrom, each battery being elongate in a lengthwise direction; and a protection circuit module, PCM, that is electrically coupled to both of the pair of batteries (103, 103') and that is configured to control one or more functions of the batteries, the PCM comprising: a protective circuit board, PCB, electric coupling of the pair of batteries (103, 103') to the PCM being via connection of the respective electrodes (109, 109') of both of the pair of batteries to the PCB; and electronic PCM components mounted on the PCB, wherein the respective lengthwise dimensions of the pair of batteries (103, 103') are parallel and in line with one another, the batteries lying substantially in a common plane, with a longitudinal spacing between adjacent ends of the batteries, the PCM being located within the longitudinal spacing between the batteries (103, 103'); wherein the PCB has a pair of parallel major faces (124, 125) and a thickness dimension, the thickness dimension being defined by a transverse spacing between the parallel major faces (124, 125); wherein the electronic PCM components are mounted on both of the parallel major faces (124, 125); and wherein the PCB is oriented such that the thickness dimension of the PCB extends in the lengthwise direction of the aligned batteries and each of the major faces (124, 125) of the PCB faces toward a respective one of the batteries (103, 103') between which the PCM is located. a pair of physically separate electrochemical batteries (103, 103'), each battery being an elongate modular unit having a respective pair of electrodes (109, 109') projecting therefrom, each battery being elongate in a lengthwise direction; and a protection circuit module, PCM, that is electrically coupled to both of the pair of batteries (103, 103') and that is configured to control one or more functions of the batteries, the PCM comprising: a protective circuit board, PCB, electric coupling of the pair of batteries (103, 103') to the PCM being via connection of the respective electrodes (109, 109') of both of the pair of batteries to the PCB; and electronic PCM components mounted on the PCB, a protective circuit board, PCB, electric coupling of the pair of batteries (103, 103') to the PCM being via connection of the respective electrodes (109, 109') of both of the pair of batteries to the PCB; and electronic PCM components mounted on the PCB, wherein the respective lengthwise dimensions of the pair of batteries (103, 103') are parallel and in line with one another, the batteries lying substantially in a common plane, with a longitudinal spacing between adjacent ends of the batteries, the PCM being located within the longitudinal spacing between the batteries (103, 103'); wherein the PCB has a pair of parallel major faces (124, 125) and a thickness dimension, the thickness dimension being defined by a transverse spacing between the parallel major faces (124, 125); wherein the electronic PCM components are mounted on both of the parallel major faces (124, 125); and wherein the PCB is oriented such that the thickness dimension of the PCB extends in the lengthwise direction of the aligned batteries and each of the major faces (124, 125) of the PCB faces toward a respective one of the batteries (103, 103') between which the PCM is located.