Abstract: A device for determining the charge condition of a secondary electric storage battery, and including a digital integrator comprising a pulse generator for producing pulses at a frequency proportional to the magnitude of the instantaneous battery current, and an up-down counter for counting the pulses in a sense (i.e. up or down) dependent upon the battery current direction. A switching arrangement operates to couple selectively the pulse generator or an adjustment pulse generator to the counter, and a comparator controls the supply of pulses to, and the sense of counting in the counter, when the adjustment pulse generator is coupled thereto in accordance with the result of a comparison of the counter setting and of a function signal.

Abstract: Apparatus for indicating the charge condition of a secondary cell, comprising an integrating device which progressively sums the ampere-hours drawn from the cell, and a computer which is programmed to provide a voltage output whose magnitude indicates the total number of ampere-hours available, from the battery at the particular discharge current and temperature. A comparator subtracts from this a voltage derived in accordance with the output of the integrating device. The comparator output thus indicates the remaining ampere-hours available to be drawn from the cell at the prevailing conditions of discharge current and temperature. There may be provided a further computer which is programmed in accordance with the variation in minimum ampere-hour requirement of the cell to ensure that a particular load, e.g. a starting motor, can be successfully operated at various temperatures.