The situation you are describing is a classic "low-voltage lockout" scenario common in Victron Energy Storage Systems (ESS). The primary cause for the battery discharging despite the scheduled charge window is a conflict between the ESS "Scheduled Charging" logic and the high current draw of the Electric Vehicle (EV) charger occurring before the grid-parallel window opened. Because the EV started at 11:00 PM and your grid-use window was set for 11:30 PM, the Victron system attempted to cover the massive AC load from the battery to maintain the "Grid Setpoint" (usually 0W), leading to a rapid depletion below the Battery Management System (BMS) cut-off threshold.[1]

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To understand why this happened, we must look at the logic of the Victron Color Control GX or Cerbo GX. When a high-power appliance like an EV charger (typically drawing $7kW$ to $11kW$) activates outside of a "Scheduled Charge" or "Inverter Restricted" window, the ESS sees this as a standard household load. If the battery was already at a low State of Charge (SoC), the high discharge rate caused a significant "voltage sag." Even if the resting voltage was safe, the instantaneous voltage likely dropped below the "Sustain Voltage" or the BMS "Under-Voltage Protection" (UVP) limit, causing the BMS to open its internal contactors to prevent permanent cell damage.[2] At 50V, a standard 48V nominal lithium battery (LiFePO4) is at a very low state, and if the BMS has disconnected, the Victron inverter cannot "see" the battery to start charging it, resulting in the "Idle" state.[3]

To resolve this and "wake up" the battery, you should follow these logical steps:

1. Force a Charge from the Grid: In the Victron Remote Management (VRM) portal or the GX device menu, go to Settings > ESS and change the "Mode" to "Keep batteries charged." This overrides all schedules and instructs the MultiPlus/Quattro to prioritize battery recovery.[1]
2. BMS Reset/Jumpstart: If the battery is "stuck" and not accepting a charge, the BMS has likely entered a protection mode. Many batteries (like Pylontech or BYD) have a "Wake Up" button or require a brief application of voltage to the terminals to close the contactors. If your inverter shows 0V on the DC bus, you may need to temporarily use a dedicated standalone charger or a "dead battery recovery" function if your specific battery model supports it.[4]
3. Check the "Sustain" Voltage: Ensure your "Sustain" voltage in the ESS menu is set correctly (typically around $50V$ to $51V$ for a 48V system). If the battery stays at 50V and won't move, the inverter may be waiting for the voltage to rise above this threshold before it initiates a full bulk charge.[2]
4. Adjust EV Scheduling: To prevent a recurrence, ensure your EV charger is integrated with the Victron system via Large OS (Node-RED) or use a smart EVSE (like the Victron EV Charging Station) that communicates directly with the GX device to ensure it only draws power when the grid is active or the battery is above a specific SoC. [5]

The most likely cause was the EV charger drawing power at 11:00 PM while the ESS was still in "Discharge" mode, causing the battery to hit its low-voltage cut-off; to wake it up, you must set the ESS to "Keep batteries charged" and potentially use a "BMS wake-up" procedure or a manual charge to bring the voltage back above the inverter's starting threshold. [1] [3]