GB1316169A - Battery charging system - Google Patents

Abstract

1316169 Charging batteries SINGER CO 29 Dec 1970 61547/70 Heading H2H A battery charging system comprises means whereby the charging rate can be varied in dependence upon the overall temperature of the battery and the temperature of an individual cell of the battery. A battery 1 is charged from an A.C. source 10 by way of a transformerrectifier unit and two switching circuits 40, 70, the circuit 40 being effective to allow the battery to be charged when the battery temperature is within predetermined limits-say 0‹-50‹ C.- and the circuit 70, in the form of a Schmidt trigger circuit, controls the high and low rate charging of the battery in accordance with the temperature of an individual cell. The battery 1 is formed by a plurality of "active" cells and one passive cell having a heater 9 associated therewith, the heater 9 being connected in the battery discharge circuit, a thermistor 88 being associated with the passive cell and placed in the switching unit 70 so that a high battery discharge current does not distort the operation of the switching circuit 70. Two thermistors 52, 54 are located to sense the overall temperature of the battery 1 and when the battery temperature is within the desired limits the resistances of the thermistors are such that the transistors 42a, 42b, 58 function to make a transistor 60 conductive thus placing a conductor 62 at a D.C. potential. Thermistors 82, 84, 86 are located to sense the temperatures of "active" cells in the battery 1 and these thermistors together with thermistor 88 located in the "passive" cell, are effective to control a transistor 72a. Whilst the temperatures of these cells are normal the thermistors function such that transistor 72a is "OFF" and transistor 72b is "ON". This causes a transistor 90 to conduct which then turns transistors 100, 102 on. Transistor 102 carries the battery charging current and since a resistor 104 is of low value a high charging current results. When the battery 1 is fully charged, the temperatures of the active cells become higher than that of the passive cell when the conditions of the thermistors 82-88 as such to switch the circuit 70 to its other state. Thus transistor 102 is turned off and the high charging current terminated. A transistor 108, in parallel with the transistor 102, is turned on whenever the conductor 62 is energized, thus a trickle charge by way of a high value resistor 110 is always maintained. Should the battery become so charged that gassing begins, a Zener diode 122 breaks down to render a transistor 120 conductive which in turn cuts off transistor 108 to terminate the trickle charge process. When the circuit 70 has been switched to its other state to terminate the high charging current the circuit is so arranged that it is necessary to switch off the main supply 10 to reset the circuit. If desired the circuit 40 may be similarly arranged.