Uninterruptible power supply battery voltage monitor composed of NE555

As shown in the figure, this is the battery voltage monitoring circuit of the uninterruptible power supply. The circuit consists of a sampling circuit, a bistable circuit IC2, and a relay J1. The sampling circuit is divided into an upper limit sampling circuit and a lower limit sampling circuit. The upper limit sampling circuit composed of the voltage network R3, W2, and R4 is connected to the 6th pin of the IC2 (555) bistable circuit, and the lower limit sampling circuit composed of the voltage network R1, W1, and R2 is connected to the trigger terminal 2nd pin of IC2. When the battery voltage makes the potential of the 2nd pin lower than 1/3VDD, the 555 is set, the high level output by the 3rd pin causes J1 to attract, the contact J1-1 is connected, and the charging circuit starts charging. When the battery voltage is charged high enough to make the potential of the IC2 6th pin higher than 2/3VDD, the 555 is reset, the low level output by the 3rd pin causes the relay J1 to release, the contact J1-1 is disconnected, and the charging circuit stops charging, thereby keeping the battery voltage within a certain voltage range.

This circuit can monitor the high and low voltage of the battery and automatically connect or disconnect the charging circuit to ensure that the battery has enough energy storage and extend its life.