Batterie lithium bloquée : Débloquer BMS PACE Delong + Deye

The lithium batteries in the Delong Top Energy range equipped with a PACE (Protection And Control Electronics) BMS are high-performance, reliable storage solutions. However, like any sophisticated protection system, the BMS can sometimes go into safety mode and block the battery, leaving the user in a confusing situation: the battery communicates with the inverter, displays a SOC (State of Charge) of 50% or more, but delivers no output voltage (0V).

In this technical article, we will detail the causes of this lockout, explain how to correctly interpret the monitoring data of a Deye installation, and, above all, guide you step by step through the procedures for unlocking the PACE BMS.

🔍 Understanding the PACE BMS: Architecture and Role

The PACE BMS (used by Delong, Seplos, and other manufacturers) is an advanced battery management system that performs three critical functions:

• Cell protection: Real-time monitoring of the voltage, temperature, and current of each LiFePO4 cell.
• Active balancing: Redistribution of energy between cells to maintain pack consistency.
• Communication protocol: RS232/RS485/CAN interface for communication with the inverter.

Key point: The BMS uses MOSFETs (power transistors) as "electronic switches" between the cells and the output terminals. When protection is activated, these MOSFETs open instantly, physically cutting the circuit. This is why you measure 0V at the terminals while the battery contains approximately 52V inside.

📊 Case study: Analysis of a real blockage

Let's take a concrete example of a Deye 6kVA single-phase installation + Delong 15kWh battery where the battery refuses to wake up. Here is the data recorded in the Deye monitoring interface:

🔬 Technical Diagnosis

The analysis reveals a software lockout of the BMS characterised by the opening of the discharge MOSFETs, even though the internal voltage is 52.68V. The BMS sends a formal command to the inverter to prohibit any current draw.

⚠️ The 5 Causes of PACE BMS Safety Lockout

1. Short Circuit Protection

Trigger: The BMS detects a sudden current surge exceeding 300-400A for a few microseconds. This often occurs when the battery circuit breaker is closed in the presence of empty capacitors in the Deye inverter.

2. Under Voltage Cell

Trigger: A cell drops below 2.0V. Even if the SOC displays 50%, an unbalanced cell can force a shutdown.

🛠️ Step-by-step unlocking procedure

Step 2: Hard Reset via the Physical Button

According to the official Delong manual, the ON/OFF button has a built-in "Reset" function:

1. Isolate the battery: Open the DC circuit breaker and disconnect the communication cable.
2. Force shutdown: Press and hold the ON/OFF button for more than 5 seconds.
3. Wait: Wait 30 seconds to clear the BMS RAM.
4. Restart: Press ON/OFF for 1 to 2 seconds. If the ALM LED remains off, the system is unlocked.

📱 Intelligent Monitoring: Preventing Lockouts

📞 Need help? Contact us:
Wattuneed – Rue Henripré 12, 4821 Andrimont, Belgium
+32 87 45 00 34 – info@wattuneed.com