Emergency power supply with battery - has charge-state tester switched periodically to AC mains and measuring voltage across load

摘要

The power supply has a battery constantly charged from the mains and supplying the load when the mains fails. A battery tester (7) is connected in parallel with the load (4) in order to check the charge state of the battery (2). The tester compares the voltage drop across the load with a reference voltage derived from the mains (20). A change-over switch (8) is connected to the a.c. input of the battery charger (1) and switches the a.c. mains either to the a.c. input of the charger or to the tester. The change-over switch is operated manually or automatically at periodic intervals. The advantage lies in being able to check the battery with provision for an alarm condition and without having to disconnect the mains by removing the fuse.