GB1125351A - Improvements relating to the testing of electrical storage batteries - Google Patents

Abstract

1,125,351. Battery testing. M. L. AVIATION CO. Ltd. April 11, 1967 [Jan. 11, 1966], No. 1297/66. Heading G1U. [Also in Division G3] An apparatus for indicating the power capacity of a storage battery has an adjustable load connected across the battery together with a current detector which operates in response to current changes in the load to adjust the load through a feedback circuit to maintain the current constant. The time taken for the battery voltage to drop to 85% of its initial value under the constant current conditions is then determined, to indicate the battery capacity. The circuit for establishing a constant battery discharge current is connected between terminals C+ and C-, and the current from C+ first passed through a rectifier circuit D20, where a further voltage from an A.C. source may be added if the battery voltage is small, and then passes via a meter A to the load bank including the resistors R39-R50 in the emitter circuits of transistors VT1-VT12. After passing through this load, the current passes to the C- terminal via either R38 or R1. The voltage across this resistor is applied via line as to one side VT13 of a double transistor whose other side is connected to a reference potentiometer VR2. The differential output from this double transistor amplifier is amplified through VT15, VT16 and VT17 and applied via line as to control the transistors VT1-VT12. Thus any change in the current through the load bank causes the load impedance to change in a compensating way. The various sets in the switch SW2 enable battery voltage range changing to be accomplished, and those in SW3 enable a coarse control over the discharge current to be established . The voltage across the battery terminals at V+, V- is applied to VT19 in a double transistor whose other member VT20 is controlled by a reference voltage set at VR1 to be 85% of the fully charged battery voltage. The output voltages from this double transistor are applied to the halves of the long-tailed pair VT22, VT23, whose output is amplified through VT24 and VT25 to operate relay RL1. One of the contacts of this, RL1/4, is changed to apply a supply to an oscillator VT26 whose output pulses are counted at C. When the input voltage falls below the reference, the relay changes, and the counter stops. Alarm 4 sounds and a lamp L2 lights to indicate the end of the test, and the number in the counter gives the test result. Other relay contacts operate to disable the parts of the circuit at the end of the test.