Target keywords: LiFePO4 module replacement, battery pack failure, LFP troubleshooting, cell imbalance fix
Meta Title: Handling Partial Pack Failures in LiFePO₄ ESS | Module Replacement Guide
Meta Description: Learn how to identify weak or failed modules in a LiFePO₄ energy storage system and replace them safely with proper balancing and commissioning steps.
Summary
When one module in a LiFePO₄ battery bank fails, users often wonder whether the entire battery needs replacement. Usually, only the defective module requires replacement — but the procedure must be done correctly to avoid imbalance or system failure.
How to Identify a Failed Module
Key indicators:
- Voltage collapse under load
- Significantly higher internal resistance
- Persistent undervoltage alarms
- Thermal anomalies
- Module not balancing with others in the pack
- BMS logs showing repeated shutdowns in the same module position
Step-by-Step Replacement Procedure
1. Isolate the system
- Turn off inverter
- Disconnect AC & DC
- Open main DC breaker
2. Measure voltages
- Ensure replacement module voltage ≈ existing modules (difference < 0.05–0.1 V for best results).
3. Install new module
- Torque busbars to spec.
- Ensure series/parallel configuration matches original design.
- Connect BMS communication leads.
4. Balancing procedure
Two methods:
A. Top Balancing (Recommended)
- Charge all modules to identical full-charge voltage.
- Allows BMS to perform precision balance at upper SOC.
B. Bottom Balancing
- Discharge pack to low SOC together.
- Balance at low voltage levels (used in off-grid installations).
5. Commissioning
- Run 1–3 shallow cycles.
- Monitor temperature, cell voltage deviation.
- Verify BMS communication and SOC accuracy.
Common Mistakes
- Installing a module with very different SOC → leads to overvoltage or undervoltage events
- Mixing different brands or cell grades
- Ignoring torque specifications
- Forgetting to re-enable BMS communication chain
- Skipping balancing steps
Best Practices
- Purchase modules from same manufacturer and same production batch if possible.
- Always log serial numbers and test values before installation.
- Perform periodic IR comparison to spot weak modules early.
Quick FAQ
Q: Can I replace just one cell inside a module instead of the full module?
A: Not recommended unless you are a certified technician. Cell mismatch and safety risks make full module replacement the safer approach.