GB1233186A - - Google Patents

Abstract

1,233,186. Charging batteries. ELECTRIC POWER STORAGE Ltd. 25 Feb., 1969 [26 Feb., 1968], No. 9180/68. Heading H2H. A battery charging circuit applies current to the battery intermittently, the duration of the "off" periods depending on the fall in battery voltage during these periods. The charge is terminated or modified by a device which is responsive to a function of the duration of the off-periods. In the arrangement shown in Fig. 1, a battery is charged from an A.C. source 8, 9 by way of thyristors 5, 6, a transformer 4 and rectifier bridge 1. Connection of the battery to terminals 2, 3 causes current to flow through relay coils 28 and 30 resulting in the closure of contacts 30/3 and 30/4 amongst others and so allowing charging to begin. At the same time, a timer 10 and its associated clutch 11 are energized and these run for a preset time before opening contacts 10/1 to de-energize relay 30 and interrupt the charging. The timer 10 resets to its initial position, whilst closure of contacts 30/2 starts the operation of a "total off" timer 15. Now that charging has ceased, the battery voltage begins to fall, and when it reaches a predetermined level a Zener diode 31 conducts, switching on transistors 12 and 32. Relav 30 again operates and another period of charging begins. However, the clutch 16 of the timer 15 is not reset, so subsequent off periods are recorded cumulatively by the timer 15. After a number of cycles, the total off time reaches a preset level, and then the timer 15 energizes a relay 29 which modifies the circuit so that charging occurs only if the battery voltage falls below a certain value. When this happens, the battery is charged for a fixed time determined by a further timer 13. In a modification, Fig. 2 (not shown), the first stage of the charging cycle is ended when the relative increase in duration of an off period compared with the preceding period falls below a predetermined amount, e.g. 10%. This is achieved by replacing the total off timer 15 with a reversible motor which is driven in opposite directions during alternate off periods and is arranged to run 10% slower in the reverse direction. The second phase of the charging only begins when the motor fails to regain its initial position before the current off period finishes.