GB516135A - Improvements in or relating to battery charging systems - Google Patents

Abstract

516,135. Charging batteries. STANDARD TELEPHONES AND CABLES, Ltd., HARTLEY, G. C., and RICHARDS, E. A. June 21, 1938, No. 18421. [Class 38 (iv)] A thermally-operated relay connected across battery charging leads and arranged to insert into the charging circuit a device, e.g., resistance or counter e.m.f. cell to reduce the charging current when a certain voltage has been reached causes also an increase in the current through its heating winding to prevent release until a predetermined voltage fall has occurred. The contacts of the relay REL, Fig. 1, which may be of vacuum type, may open on operation and be in shunt to a resistance R1. Alternatively they may be normally open and energize on closure a second thermal relay REL2, Fig. 2, with contacts in shunt with the resistance. The relay REL1 may be connected to a point in the resistance R1 which is adjustable to determine the voltage range and a rheostate R2 may determine the operating voltage. To eliminate the influence of supply voltage and rectifier characteristics relays may be across battery terminals as shown in Fig. 5, the relay REL2 normally shunting the relay REL 1 which is in series with a rheostat R2 determining the maximum battery volts at which it operates to cause relay REL2 to remove the shunt and to insert the instance R1. A modification in which the relay REL1 has normally open contacts shunting the heating winding of relay REL2 is described. To permit a charge to continue longer at full rate to compensate for excessive fall in battery volts due to supply failure a second set of relays REL3 and REL4 may be added, as shown in Fig. 5, arranged to operate and release at wider voltage limits than the first.