Initial coolant filling is a critical commissioning milestone for liquid-cooled Battery Energy Storage Systems (BESS). Improper execution can cause severe airlocks, localized cell overheating, or catastrophic fluid leaks. Operators must strictly adhere to this standardized six-step protocol to ensure long-term thermal management reliability.

1. Pre-Check and Pressure Testing

• Leak Detection: Conduct a 24-hour nitrogen pressure holding test (typically at 0.4–0.6 MPa) before introducing any liquid.
• Joint Inspection: Verify all quick-connect couplings, manifold joints, and thermal insulation jackets are fully secured.
• Media Verification: Confirm the coolant spec matches requirements (e.g., 50/50 premixed ethylene glycol and deionized water).

2. Deep System Evacuation

• Airlock Prevention: BESS piping is extensive; filling at atmospheric pressure guarantees trapped air.
• Vacuum Pull: Connect a heavy-duty vacuum pump to seal off the loop. Pull a deep vacuum to remove all moisture and air pocket potential.

3. Segmented Initial Injection

• Cluster Isolation: Open valves grouping by grouping (or rack by rack) to ensure uniform fluid distribution.
• Priming Fluid: Pump coolant into the low-point service valve until the pressure gauge reads a stable 0.6 to 1.2 Bar.
• Bleeding Valves: Keep high-point manual bleed valves cracked open until a steady stream of fluid—free of foam—emerges.

4. Dynamic Circulation & De-Aeration

• Pump Control: Power on the BESS Chiller/HVAC unit in "Manual Circulation Mode" (run the pump only; keep the compressor off).
• Air Expulsion: Circulate the fluid for 15–20 minutes to force micro-bubbles out of the cold plates and into the expansion tank.
• Pressure Monitoring: Watch for pressure drops as trapped air is displaced by the moving fluid.

5. Secondary Top-Up & Stabilization

• Final Pressure Adjustment: Top up the system until the static pressure locks firmly between 1.2 and 1.5 Bar.
• Level Check: Ensure the expansion tank sight glass reads precisely between the MIN and MAX thresholds.
• System Sealing: Securely lock all manual bleed valves and disconnect the external filling rig.

6. Full-Load Commissioning

• Active Thermal Run: Engage full heating and cooling modes to run the system under simulated operational stress.
• Leak Detection: Monitor the container floor leak-detection cables and bilge level sensors for any moisture alarms