SE337058

1,146,563. Battery charging systems. INTERNATIONAL STANDARD ELECTRIC CORP. 17 March, 1967 [18 March, 1966], No. 12672/67. Heading H2H. Self-service battery charging apparatus of the type in which the customer inserts one or more coins to determine the charging time, comprises a conventional fixed polarity charging unit I and a coin-operated control device 2 which includes a run-down clock 4 and means to detect the polarity of the connected battery 3 and to operate change-over switches accordingly so that the battery is correctly connected to the charger 1. The battery polarity is detected by the circuit comprising relays K2, K3, diodes 10, 11 and a current-limiting non- linear resistor 9, the relays K2, K3 respectively controlling contacts K21, K22, K23 and K31, K32, K33. Connection of the battery 3 to terminals 12, 13 causes actuation of the appropriate relay and connection of the battery to the charger terminals 14, 15 through a high resistance 8 which permits only negligible charging current to flow. Timer contacts KF are closed by insertion of the first coin and remain so until the expiry of the selected time period, which is determined by the momentary closure of contacts KM each time a coin is inserted. Initially the simultaneous closure of contacts KF, KM energizes a self-locking relay K1, so that the resistor 8 is shunted by two circuits comprising resistors 5, 6 and resistor 7, relay K1. This allows the flow of substantial charging current whose value is maintained relatively constant by making the resistor 5 non-linear. This charging current continues to flow until contacts KF open or until the battery is disconnected (should this occur before the expiry of the selected time), such disconnection de-energizing relay Kl whose selflocking contacts K11 open to restore the charging circuit to the stand-by condition (resistor 8 only). The polarity detector and switching part of the apparatus may be modified, e.g. by using two polarized relays or a single magnetic polarized relay having a neutral mid-position.