Fault

C04

Cell undervoltage.

17 Devices that report this code

What does the C04 error code mean?

C04 on a Felicity unit indicates: Cell undervoltage.. It is a fault-severity event that can appear on 17 different devices in the Felicity catalog. The same code may have slightly different recommended fixes depending on the device — the per-device sections below show the exact wording from each device's official manual.

This is a fault-severity code

Fault codes stop normal operation but the unit may attempt to recover. Common causes are out-of-range conditions (voltage, current, temperature) that require checking inputs and outputs before restart.

What triggers this code

C04 is triggered when the unit's protection or monitoring logic detects the specific condition described above. The exact trigger depends on the device — see the per-device sections for the official manual entry for each.

FLA12100Battery↗ view on device
C04Cell undervoltage.Fault
Description

Cell undervoltage fault. LED pattern: LED1 OFF, LED2 OFF, LED3 ON, LED4 OFF.

Recommended fix

Restart the unit. if the error persists, contact the repair center.

Source:Felicitysolar FLA12100 12.5Kwh Battery Energy Storage System User Manual.pdf · page 1
FLA48200Battery↗ view on device
C04Cell undervoltage.Fault— high
Description

Individual cell voltage dropped below the lower limit.

Recommended fix

Restart the unit. if the error persists, contact the repair center.

Source:Felicitysolar FLA48200 48V 200Ah 10kWh Lithium Phosphate Battery User Manual.pdf · page 12
FLA48250Battery↗ view on device
C04Cell undervoltage.Critical
Description

Individual cell voltage has fallen below its lower protection threshold.

Recommended fix

Restart the unit. if the error persists, contact the repair center.

Source:6peluqppy_66a93554057c8.pdf · page 12
FLA48250-EUBattery↗ view on device
C04C04Fault
Description

Cell undervoltage.

Recommended fix

Restart the unit. if the error persists, contact the repair center.

Source:FLA48250-EU_Manual.pdf · page 8
FLA48500Battery↗ view on device
C04Cell undervoltage.Fault
Description

Individual cell undervoltage protection triggered.

Cause

One or more cells dropped below the per-cell lower voltage limit.

Recommended fix

Restart the unit. if the error persists, contact the repair center.

Source:felicitysolar FLA48500 LiFePO4 Battery System for Households User Guide.pdf
FLS48100SG2Battery↗ view on device
C04Zell-Unterspannung.Fault
Description

Cell undervoltage. Voltage of a single cell fell below the rated lower protection threshold.

Cause

Cell voltage below protection value during discharge (Zellenspannung unter dem Schutzwert).

Recommended fix

Restart the unit. if the error persists, return to repair centre.

Source:Benutzerhandbuch - Felicity FLS48100SG2.pdf
HE-GF-FLA-48500Battery↗ view on device
C04Cell undervoltage.Fault
Description

Individual cell undervoltage protection triggered.

Cause

One or more cells dropped below the per-cell lower voltage limit.

Recommended fix

Restart the unit. if the error persists, contact the repair center.

Source:HE-GF-FLA-48500 Manual_20250327_EN.pdf
LPBF48100-MBattery↗ view on device
C04Single cell undervoltage.Fault
Description

Individual-cell under-voltage fault displayed on the LCD BMS fault code / flag screen (section 4.4); one or more cells fell below the lower cell-voltage limit.

Cause

Deep discharge or a weak / aged cell pulling below the under-voltage threshold.

Recommended fix

Restart the unit, if the error persists, contact the repair center.

Source:358-010291-07.pdf · page 8
LPBF48200-HBattery↗ view on device
C04Single cell undervoltage.Fault
Description

An individual cell voltage has dropped below the protection limit.

Cause

One cell voltage below safe lower threshold (cell imbalance or over-discharge).

Recommended fix

Restart the unit; if the error persists, contact the repair center.

Source:Manual-LPBF48200-H.pdf · page 10
LPBF48350Battery↗ view on device
C04C04Fault
Recommended fix

Restart the unit, if the error persists, contact the repair center.

Source:Felicitysolar LPBF48350 17.5kWh 48V Solar Battery Pack with BMS User Guide.pdf
LUX-E-48100LG03Battery↗ view on device
C04Cell undervoltage.Fault
Cause

An individual cell voltage fell below the lower protection threshold.

Recommended fix

Restart the unit. if the error persists, contact the repair center.

Source:LUX-E-48100LG03-Lithium-Battery-User-Guide.pdf · page 12
LUX-E-48200LG03Battery↗ view on device
C04C04Fault
Recommended fix

Restart the unit. if the error persists, contact the repair center.

Source:LUX-E-48200LG03-Lithium-Battery-User-Guide.pdf · page 12
LUX-E-48230LG03Battery↗ view on device
C04C04Fault
Recommended fix

Restart the unit. if the error persists, contact the repair center.

Source:LUX-E-48230.250LG03-Lithium-Battery-User-Guide.pdf
LUX-X-48050LG01Battery↗ view on device
C04C04Fault
Description

Cell undervoltage.

Recommended fix

Restart the unit, if the error persists, contact the repair center.

Source:LUX-X-48050LG01-low-voltage-battery-user-guide.pdf · page 17
LUX-X-48100LG01Battery↗ view on device
C04Cell undervoltage.Critical
Description

An individual cell voltage has dropped below its lower protection threshold.

Recommended fix

Restart the unit; if the error persists, contact the repair center.

Source:LUX-X-48100LG01-Litium-Battery-User-Guide.pdf · page 17
LUX-X-48100LG01-USBattery↗ view on device
C04Cell undervoltage.Critical
Description

An individual cell voltage has dropped below its lower protection threshold.

Recommended fix

Restart the unit, if the error persists, contact the repair center.

Source:358-S010024-03LUX-X-48100LG01-User-manual_compressed.pdf · page 23
LUX-Y-48280LG01Battery↗ view on device
C04Cell undervoltage.Fault
Cause

An individual cell voltage fell below the lower protection threshold.

Recommended fix

Restart the unit. if the error persists, contact the repair center.

Source:LUX-Y-4828048300LG01-Lithium-Battery-User-Guide.pdf · page 8

Frequently asked about C04

What is the C04 error on Felicity?
C04 on a Felicity unit means: Cell undervoltage.. It can appear on 17 different devices in the Felicity catalog. The cause and recommended fix are listed for each device on this page.
Can I clear the C04 code myself?
It depends on the severity. Warning-level codes can usually be cleared by following the recommended fix. Fault and critical codes often require checking the source condition first; if the code returns immediately after restart, escalate to authorized service.
Is the C04 fix the same on every device?
The cause is consistent — it's the same protection logic. The exact fix wording can differ per device because each official manual addresses model-specific context (input ranges, parallel-config notes, firmware revisions). Use the per-device section that matches your unit.
Where does this information come from?
Every entry is sourced directly from the official Felicity user manual for the affected device. The "Source" line at the bottom of each device's section shows the manual filename and page number.

Compiled from official Felicity user manuals. Always consult your device manual and a qualified technician before performing repairs.