Patent GB-1428671-A (GB)
Title: Automatic battery-charging
IPC: H02J7/00
Filed: 1972-05-04
Abstract: 1428671 Charging batteries HARMER & SIMMONS Ltd 24 April 1973 [13 March 1972 4 May 1972] 11611/72 and 20792/72 Heading H2H A method of charging a battery, particularly a lead acid battery, comprises charging the battery at a first high current rate until a predetermined battery voltage is reached after which the battery is charged at the first rate or at a second rate less than the first charging rate, the charging current is periodically measured to determine whether or not the battery is fully charged. A battery 2 is charged from an A.C. source by way of a charging device 1, a triac 3 being rendered conductive when the high charging current is required and the triac 4 when a reduced charging current is required, the gate signals for the triacs being developed by oscillators 11, 12 respectively, shown in Fig. 2. The battery voltage is applied to a terminal 2<SP>1</SP> and thence to a voltage level detector 5 which is connected to an oscillator 6. Until the battery voltage attains a predetermined level there will be no output from the detector 5 and hence the oscillator 6 will not run and the counters 7 will remain at zero. Under these conditions the states of an OR gate 8, inverter 9 and OR gate 10 will be such that the oscillator 11 will supply a signal to the triac 3 to cause the battery 2 to charge at the full rate. During this operation the oscillator 12 is inhibited by an interlock 13. When however, the battery voltage reaches the predetermined level, detector 5 provides an output to ram the oscillator 6 whereupon the counters 7 run to time the running of the oscillator. When the counters reach 128 (2 hours) the signal to the oscillator 11 via the elements 8, 9, 10 is removed and the triac 3 switches off. The output of the detector 5 is also applied to a mono-stable multivibrator 14 and thence to a whole cycle device 15 wherein a thyristor is used which is controlled to conduct for a number of whole cycles of an A.C. supply 25 for a given period. The oscillator 12 and thus the triac 4 are controlled to give a constant voltage float charge with a reduced current value. The oscillator 11 is inhibited by the interlock 13 during this operation. After a further period of operation of the oscillator 6 (1¢ minutes) a signal is passed to an OR gate 17, then to an AND gate 18 between an average converter 19 and a level detector 20. The input to the converter 19 is from the multivibrator 14 and if the charging current at this point is high, the level detector 20 will energize the oscillator 11 by way of OR gate 10 causing the triac 3 to conduct to charge at the full rate. OR gate 17 receives signals for a count of 8 + 4 + 2 + after which the sampling cycle is repeated. When the level detector 20 produces an output representing a low charging current or the counter 7 counts out a signal is passed from the detector 20 via an OR gate 21 to the oscillator 6 thus stopping the oscillator 11 and energizing the oscillator 12 to maintain a float charge for the battery. Various other logic elements are provided to reset the counters 7 if the A.C. supply is removed or the battery disconnected. Other embodiments are described wherein the charge rate during sampling is restricted to the full charge rate only.