Sleep Mode Symptoms

LFP Battery Sleep Mode — Symptoms

When an LFP battery enters BMS sleep mode (standby), the cells are normal, but the BMS turns the output off to save power. The battery may appear “off” until awakened.

Common symptoms

• No voltage at terminals (0–1 V)
  → Discharge MOSFET is off

• Electronics or engine will not power on

• Charger shows “no battery” initially

• Bluetooth still connects (app shows Sleep/Idle)

Key clue

Battery voltage is visible in the app (~13 V), but not at the terminals until wake.

Wake behavior

Applying a charger or small load turns the battery on and restores terminal voltage.

Sleep vs Protection

• Sleep: no fault, wakes normally

• Protection: fault present, may not wake

Note (cranking batteries):
A proper marine cranking BMS should wake instantly and allow engine start.