Abstract: Apparatus for monitoring the capacity of a battery of series-connected storage cells (10) which are tested by discharging the battery at constant current. The apparatus comprises: sequencer means (30, 40, 50) for cyclically addressing each battery cell in turn, and delivering a single measurement signal (V.sub.M) representative of the voltage across the terminals of the cell being addressed; comparator means (60) connected to receive said single measurement signal and to deliver an active output condition when said single measurement signal (V.sub.M) is below a threshold value (V.sub.REF) representing the end-of-discharge voltage for the cells under test; and timer means (90, 91) responsive to said active output condition to indicate the discharge time of the cell responsible for causing said active output condition to be delivered.Cyclic operation of the apparatus is interrupted each time a cell is encountered with less than the threshold voltage across its terminals.