NR BR 955 PDF

GENERAL

This Specification covers chargers of the constant potential type, i.e. a high initial charge is to be provided when the cells are in a low state of charge, and the rate of charge is automatically to topper off to a value adequate to maintain the cells in a fully charged state. Batteries of either the lead/acid or the alkaline type may be used provided the appropriate number of cells are connected in series. No adjustment of the charge characteristics is needed to suit the two different types of battery.

This Specification does not cover battery chargers:-

(a) for use with Aster track circuit equipment

(b) other than constant potential type

(c) For telecommunications purposes

The unit shall consist of a transformer, rectifying and regulating means, a power-off detector when ordered, and fuses, all suitably connected and mounted and with the appropriate terminals for external wiring and earthing purposes.

Means other than fuses or circuit breakers shall be incorporated to limit automatically the output current to the rating of the unit when connected to a battery in a low state of charge.

No ammeter or voltmeter shall be incorporated in the unit.

If it is necessary to make a measurement of current for the adjustment of the charger an internal shunt shall be provided. This shunt must be connected to external terminals suitable for the attachment of crocodile clips. The meter which will be connected to the terminals is a Lineman's Electrical Measuring Instrument to BR Specification No 921A. The shunt should be designed for the meter to be set to the 75 mA range when its full scale deflection is 0.15 V and it may be read on one of four ranges 75 mA, 300 mA, 1.5 A, 15 A.

Measurements which must be taken for adjustment purposes should be independent of load current.

BR Specification No. 950 shall apply to all components (including rectifiers) incorporated in the units except where any item has been otherwise specified herein.