LVD can be configured as load or battery disconnect and normally wired as battery disconnect. The LVD disconnect the batteries from the load at the preset LVD disconnect voltage after a preset time (LVD 1 only) to prevent damage to the batteries due to excessive deep discharge. The LVD then reconnects the batteries at the preset reconnect voltage after the AC powers is restored.
The SM45 Supervisory module provides two independent LVD channels for controlling up two LVD unit, LVD 1 and LVD2. LVD 1 and LVD 2 can have different disconnect and reconnect voltages or LVD1 can be set for timed disconnect.
Dual LVD control is control is typical used for urgent/non urgent load disconnect prioritization. For example during an AC, power outage where the batteries are supplying load, LVD 1 can be connected to non urgent (low priority) loads and set to disconnect before LVD2. LVD2 in turn can be connected to the system batteries. Therefore the system batteries are powering the urgent (high priority) load instead of the non urgent loads. Once the batteries have discharge to level where the preset battery termination voltage is reached, LVD2 will operate (disconnect) to prevent deep discharge of the batteries. Standard off the shelf LVD options fall into two category.
