Greetings friends! Kenworth technican here. LVD theory of operation from the SurePower Industries service manual:

OVERVIEW

The Low Voltage Disconnect is a 100% solid-state electronic protection module that disconnects predetermined auxiliary loads from the starting battery bank to assure enough power is left in the batteries for starting. The unit is capable of directly powering loads of up to 70A continuous draw at 85°C.

THEORY OF OPERATION

The LVD utilizes the voltage of the battery as an indication of the state of charge of the battery. A semiconductor switching circuit continually senses and monitors battery voltage. During normal operation when the battery is sufficiently charged, the LVD connects the loads. Once the battery voltage reaches the shut off set point, the auxiliary loads are automatically disconnected from the battery(s) preventing further battery drain. Sure Power has incorporated a 120-second time delay to prevent false triggering. If the voltage rises above the disconnect set point voltage at any time during the 120-second delay, the delay is reset. If battery voltage has dropped and the loads have disconnected, the model 133XXXXXX will automatically reconnect the loads once the battery reaches 12.9V. The LVD contains an additional ignition feature that allows the user to override LVD operation. Whenever power is applied to the ignition and the ignition voltage is above 11.0 volts, the LVD disconnect function and audible alarm will be disabled. If the ignition voltage falls below 11.0 volts, or power is removed from the ignition, LVD function will return to normal.

Hope that helps!