| 摘要 |
1,184,064. Battery testing. SMITHS INDUSTRIES Ltd. March 28, 1967 [March 28, 1966], No. 13588/66. Heading G1U. In a circuit for indicating the state of charge of an electric battery during discharge, a voltmeter 12 converts to an indication of charge a voltage which is the sum of two components, one proportional to the battery terminal voltage and the other compensating for the voltage drop across the battery internal resistance. The first component is obtained across a resistance 11 and the second at the collector of a constant current transistor 18 controlled by the voltage drop across a resistance 15 in series with the battery load. A fraction of the drop across the resistance 15 is tapped off a potentiometer 16 and is fed to the base of the transistor 18 through a second transistor 17. A diode 20 provides a variable collector load for the transistor 17 to compensate for the non-linear variation of battery internal resistance drop at low battery current Fig. 2 (not shown). The voltmeter 12 is supplied through a transistor amplifier 13, 14 and by suitable choice of the transistor 18 having a high collectoremitter resistance the resistance 11 can be omitted. In a modification Fig. 4 (not shown) the collector circuit of the transistor 17 includes a thermistor (23) heated by the current flowing through a resistance (26) in series with the voltmeter 12, so that the voltage component compensating for the battery internal resistance drop depends only on the load current and is substantially independent of battery charge. |
