An electrical connector (1) for a battery (2) comprises, electrical battery terminals (5, 6, 7, 8), a first pair of the terminals (5, 8) connecting battery cells (4) electrically in series, a second pair of the terminals (6, 7) comprising data and charging terminals, an insulating package 3 containing the cells 4 and at least a part (14) of a charging control circuit, and accessible portions (18) of the terminals (5, 6, 7, 8) being accessible through an end (19) of the package (3) and also through a side (20) of the package (3), whereby the end (19) and the side (20) of the package (3) are adapted to matingly engage another, mating electrical connector (24).