GB1272030A - Accumulator monitoring apparatus - Google Patents

Abstract

1,272,030. Monitoring the state of charge of a battery. COMPAGNIE GENERALE D'AUTOMATISME. Dec.22, 1970 [Dec. 22, 1969], No. 60813/70. Heading G1U. The state of charge of a battery 4, Fig. 1, is monitored by periodically shunting the battery by a resistor 14, thereby causing a pulse of known current I to flow through the battery in addition to the normal load current i of the battery, and by comparing the resulting change in potential across the battery with a reference potential. As described energization of a coil 10 closes a switch 11 thereby causing a monostable unit 12 to close a further switch 13, and hence to connect the shunt resistor 14, for a duration shown by waveform S 12 , Fig. 2. The monostable 12 also produces a further pulse, shown at S 16 , Fig. 2, via a delay 15 and a further monostable 16. This pulse S 16 is applied to a gate 17 to sample the resulting change in potential across the battery caused by the current pulse I, within the period during which the current pulse I is steady. To determine the change in potential across the battery, its potential prior to the current pulse I is stored on a capacitor 22. When the coil 10 is energized, the capacitor 22 is disconnected from the battery and the potentials across the capacitor and the battery are compared by a differential amplifier 20. If their difference # U exceeds a reference potential U s , derived from a regulated voltage source 23 and an impedance matching amplifier 25, a further differential amplifier 26 produces an output signal which is passed via the gate 17 to a control unit 7 to energize a battery charger 6, which remains in operation until the battery voltage U rises above a reference level U c from a second regulated voltage source 30 and an amplifier 32. The amplifier 32 includes a temperature sensitive resistor 33 immersed in the battery electrolyte in its feedback loop, to compensate for temperature variations in the battery.