Low Voltage Disconnect (LVD) unit
Protect the battery from over charging, over discharging
The lead acid batteries used in many systems are designed to be discharged by about 40 percent. If they are discharged more then 40 percent, they are will damaged.
The only way to prevent over discharge is to disconnect all the loads, and then to reconnect them only when the voltage has recovered due after charging. When over discharge is approaching, a 12 volt battery drops below 11 volts (a 24 V battery drops below 22 V).
A low voltage disconnect circuit will disconnect loads at that set point. It will reconnect the loads only when the battery voltage has substantially recovered due to the accumulation of some charge. A typical LVD reset point is 13 volts (26 V on a 24 V system).
If you have any DC loads, you should have an LVD.
Displays Low Voltage Disconnect (LVD)
Displays Low Voltage Disconnect (LVD) include a single red light to body of voltage and current. These indicators are important and useful.
Conclusion
The control of battery charging is so important that most manufacturers of quality batteries specify the requirements for voltage regulation, low voltage disconnect.
When these limits are not respected, it is common for batteries to fail after less than one quarter of their normal life expectancy, regardless of their quality or their cost.
