A low voltage battery disconnect (LVD) is a circuit which will automatically turn off the load connected to a battery if the battery voltage falls to low. Preventing lead acid batteries from being deeply discharged is absolutely key in terms of ensuring battery longevity.
Putting together a low voltage disconnect circuit is not as simple as it may initially appear. If you were to simply use a relay to disconnect the battery from the load whenever the battery voltage falls below 11.5V say, then immediately after the load is shut off, the battery voltage will jump up again re-connecting the battery to the load!
That said, it’s crucial to note that this low voltage cutoff circuit works perfectly with a gel-cell battery and 12 V car tail light. Connect your light bulb to the load output terminal. And link the power supply to the battery input terminal. Ensure that your potentiometer is set at the midpoint. Also, your variable voltage should supply 13 Volts.
In addition to taking care of hysteresis, a good low voltage battery disconnect will also include a timer. When a pump or motor is first switched on for example, the battery voltage will dip down (due to the high current required to start the pump/motor from stationary) for less than a second.
To wake up a battery that has gone into LVD, disconnect all connections from all batteries. Wait for 30 minutes, and then check the voltage of each battery individually. Label each battery and write down the voltage. If a battery has a voltage over 11.5V, charge it with a lithium charger.
A low voltage cutoff is a device that uses its circuit to turn off the load that connects to a battery automatically. Consequently, this helps to ensure the battery’s longevity. A MOSFET transistor poses as the heart of the low voltage cutoff. And the transistor works like a switch in the external circuitry’s positive line.