Low-voltage disconnect

Low-voltage disconnect (LVD) is a module or BMS feature that automatically disconnects loads from the battery when voltage drops below a critical level. It protects against deep discharge, which shortens lead-acid life and can permanently brick a LiFePO4 pack.

Typical thresholds: AGM/Gel — disconnect at 11.5–11.8 V, reconnect at 12.5 V; LiFePO4 — disconnect at 11.0–11.5 V, reconnect at 12.8 V. On LiFePO4 packs the LVD is built into the BMS. For lead-acid systems, LVD is added separately (Victron BatteryProtect, Blue Sea ML-ACR). It must NOT cut the safety loads (alarm, gas detector) — those get an unswitched feed. Without an LVD it is very easy to kill an expensive battery.