| 摘要 |
1456603 Monitoring battery charge; ELEKTRON FABRIK FUR PHYSICALISCH - TECHNISCHE GERATE KERBER & CO 16 April 1974 [26 April 1973] 16632/74 Heading G1U To measure the state of charge of a battery, the internal resistance of the battery is monitored by comparing the battery terminal voltage on load with the volt-drop across a shunt resistance in series with the battery. The terminal voltage is applied across terminals 11, 12 and thus supplies a current through resistors 24, 26, 25. The shunt resistor (15,) Fig. 1 (not shown) is connected to input terminals 13, 14 of a differential amplifier 16 having variable negative feedback 17. The amplifier output drives current through resistors 22, 26, 25. The voltage at point 23 is thus proportional to the sum of the terminal voltage and the amplifier output, which is itself proportional to the load current. By adjusting the amplifier gain using potentiometer 17, the drop in terminal voltage due to an increase in load current is equalized with the increase in the voltage across the shunt (15). Thus if the internal resistance of the battery remains constant, the voltage at point 23 remains fixed. As the battery discharges to an unsuitable level (about 80% charge) the voltage at 23 changes and this change is detected by positive feedback amplifier 43 whose output is displayed on a meter 55. The voltage at 23 is also monitored by threshold detectors 45, 44 (after filtering 38 and buffer amplification 48, 48a) which operate respectively at 80% discharge and more than 80% discharge. Detector 45 when triggered charges capacitor 67 through resistor 66 until the voltage of Zener diode 68 is exceeded at which point transistors 65, 70 conduct and energize relay 51 which operates an audible alarm. Detector 44 triggers immediately at a level below 80% discharge to energize relay 50 which shuts off the machine driven by the battery. |
