Patent GB-396823-A (GB)
Title: Improvements relating to arrangements for charging electric secondary batteries
IPC: H02J7/12
Filed: 1932-02-18
Abstract: 396,823. Charging batteries. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, CHRISTIAN, D. A., Morven, Charlton Road, Charlton, and DOUBLE, H. S., 173, Greenvale Road, Eltham, all in London. Feb. 18, 1932, No. 4851. [Class 38 (iv).] In an arrangement for charging a secondary battery during connection of the whole battery to the load the supply of charging current to one section is made to depend on the state of discharge of another section or sections. The system is specially suitable for use in telephone plant installations. Fig. 1 shows one arrangement with the load connected over leads L to a battery B divided into two sections each connected to its own current-supplying device in such a way that when one section reaches a predetermined state of discharge a comparatively heavy charging current flows to this section and causes a limitation of the current flowing to the other section. The right- and left-hand sections of the battery are supplied from the A.C. source IL through a transformer T1 and rectifier R1 and through a transformer T2 and rectifier R2 respectively. The primary circuits of the transformers T1, T2 include choke coils CH1, CH2, shunted by a condenser C1 with a series resistance RE1 and bv a condenser C2 with a series resistance RE2 respectively, the arrangement enabling tuning to be effected as described in Specification 388,772. The output circuits of the rectifiers R1, R2 include coils MC1, MC2, each comprising two coils oppositely wound, for magnetizing the cores of the choke coils CH1, CH2 respectively. The coils MC1, MC2 may be shunted by regulating resistances. Auxiliary coils AC2, AC1 in circuit with the coils MC2, MC1 are associated with the choke coils CH1, CH2 to oppose the magnetization effects of the coils MC1, MC2 respectively. With both battery sections charged the impedance of the choke coils CH1, CH2 is a maximum and little or no current flows to the battery. If, for example, the potential of the left-hand section then falls before that of the right-hand section, charging current flows through the coils MC1 and AC1 decreasing the impedance of the choke coil CH1 and neutralizing the effect of the coil MC2. A diagram is given showing the relation between the direct current output and the terminal voltage for the battery sections. Under abnormal conditions, i.e. when the voltage across the battery terminals falls below a predetermined value, the coils AC1, AC2 may be short-circuited, e.g. by a switch operated electromagnetically by a contact-operating voltmeter. Fig. 3 shows an arrangement employing change-over switches for controlling the charging of the battery sections. The battery B, across which the load is connected, is supplied through a charging switch CCO and a control switch COC from a D.C. source IL preferably derived as in Fig. 1 from an A.C. source through a transformer and rectifier. The switch CCO is in two parts each comprising a tiltable evacuated tube enclosing a globule of mercury, the mid-point of the battery being connected to the inner contacts and the ends of the battery to the outer contacts of the tubes. The switch COC comprises a similar tube with its centre contact connected to one pole of the source IL. The centre contact of the right-hand tube of switch CCO is connected to the other pole and the centre contact of the left-hand tube is connected as shown through solenoids S1, S2 to the end contacts of the switch COC. The solenoids control longitudinal movement against compression springs of a rod R arranged to operate the switches through pivoted T-members T1, T2. In the position shown the right-hand section of battery B receives charging current through the right-hand side of switch COC, solenoid S2 and right-hand sides of the tubes of switch CCO. If sufficient charging current flows, the solenoid S2 moves the rod R to the right thus tilting the switch CCO. The left-hand section of battery B then receives charging current through the right-hand side of switch COC, solenoid S2 and left-hand sides of the tubes of switch CCO. As this section becomes charged the current in the solenoid S2 becomes insufficient to hold the rod R which accordingly is restored to its mid-position under spring pressure and tilts the switch COC. The lefthand section of battery B then continues to receive a small charging current through the left-hand side of switch COC, solenoid S1 and left-hand sides of the tubes of switch CCO. When the voltage of the left-hand section has fallen sufficiently, the increased charging current energizes the solenoid S1 to move the rod R further to the left and tilt the switch CCO to its original position. The right-hand section of battery B then receives the charging current until the current through the solenoid S1 is insufficient to hold the rod R which thereupon is restored to mid-position, tilting back the switch COC and completing the cycle. The Provisional Specification refers to a further arrangement in which a charging source is disconnected from one battery section when this is fully charged and connected to another section, the change over being effected, for example, by a rotary stepping switch.