FLA48200/FLA48300/FLA48500 and LUX-Y low-voltage LiFePO4 batteries (BMS fault code list)
Felicity C04 error code
Cell under-voltage: an individual cell dropped below its lower voltage limit.
Likely causes
- Deep discharge of the pack
- A weak cell discharging faster than the rest
- Cell imbalance
- BMS cell-voltage sensing fault
Checks to run, in order
- 1Read individual cell voltages in the battery app
- 2Check how deeply the pack was discharged
- 3Compare the lowest cell with the pack average
Fixes
- Recharge the battery and allow balancing
- Reduce the depth of discharge and correct the cutoff
- Restart the unit; if the error persists, contact the repair centre
When to escalate
If the same cell stays below the limit after a full balance charge, escalate for module replacement.
Fix it with the right tools
Check the system around the fault before replacing parts: load, battery bank, PV string and commissioning settings. If you need a second opinion, send the code and your inverter model to our team.
Before you open the inverter
- Isolate both the AC and DC sides, then confirm the display is dead before touching terminals.
- Use insulated tools and one hand where possible. DC arcs do not self-extinguish like AC.
- If you see burnt terminals, swollen cells, leaking electrolyte or a burning smell, stop and escalate instead of resetting the fault.
Questions installers ask
What does Felicity C04 mean?
Cell under-voltage: an individual cell dropped below its lower voltage limit.
How do I fix Felicity C04?
Recharge the battery and allow balancing Reduce the depth of discharge and correct the cutoff Restart the unit; if the error persists, contact the repair centre
When should I escalate Felicity C04?
If the same cell stays below the limit after a full balance charge, escalate for module replacement.
Can I reset Felicity C04 myself?
Only after isolating the AC and DC sides and running the checks above. If Felicity C04 returns immediately, stop resetting it and escalate; a repeating fault usually points to a real circuit, battery or hardware problem.
Which models show Felicity C04?
Felicity C04 is documented for FLA48200/FLA48300/FLA48500 and LUX-Y low-voltage LiFePO4 batteries (BMS fault code list). Confirm the code on your own unit's display or manual before ordering parts.
More Felicity error codes
- Felicity 04Low cell voltage / over-discharge protection.
- Felicity 05PV over-current fault: the PV input current exceeded the inverter's PV input limit.
- Felicity 18PV short-circuit fault on the PV input; in the warning list the same number means battery under-voltage alarm.
- Felicity 19Battery open-circuit alarm: the inverter no longer detects a battery on its terminals.
- Felicity 20Battery SOC low alarm: the battery's state of charge has fallen to the low-SOC warning threshold.
- Felicity 21BMS communication alarm: abnormal communication between battery and inverter in non-SOC mode.
Guidance reviewed 17 October 2026 by the Mishka Energy installer team. Error codes vary by brand, model family and firmware; confirm against the manufacturer manual.
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