The circuit described right here can be used to ensure that a 12 V sealed lead acid (SLA) gel battery isn’t discharged too deeply. The predominant part of the circuit is a bistable relay, which is pushed by using the output of an op amp.
Circuit diagram :
Lead Acid Battery Protector Circuit Diagram
The battery voltage is first diminished by way of D1, R1, P1 and R2, and then repeatedly compared with a reference voltage set up with the support of diode D2. When the battery discharges too much and its terminal voltage drops beneath the level set by using P1, the output of the opamp becomes High, which causes the relay to toggle. This in turn isolates the weight from the battery. The battery will additionally be reconnected by manner of S1 once the battery has been changed or recharged.
The relay used in the prototype is a 5 V bistable type made through Omron (G6AK-234P-ST-US 5 VDC). The two windings of the relay each have a resistance of 139 Ω (for the RAL-D 5 W-K made with the aid of Fujitsu that is 167 Ω). When the battery voltage starts to develop into too low and the relay is being reset the present consumption of the circuit is ready 45 mA. Shortly after the burden has been disconnected, when the battery voltage upward throughsts above the reference voltage once more, the reset coil will no longer be powered and the current consumption drops back to about 2.5 mA.
The vary of P1 has deliberately been kept small. With a reference voltage of 5.6 V (D2) and a voltage drop of 0.64 V throughout D1, the circuit reacts within a voltage span of eleven.5 V and 11.8 V. This vary is clearly depending on the zener diode used and the tolerance.
For a larger span you can use a larger value for P1 without any problems. With the potentiometer at its mid setting the circuit switches at about 11.6 V.
Author : Jürgen Stannieder
