What is the F91 error on Felicity?

F91 on a Felicity unit means: The number of battery packs in series has not been set.. It can appear on 3 different devices in the Felicity catalog. The cause and recommended fix are listed for each device on this page.

Can I clear the F91 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 F91 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.

Fault

F91

The number of battery packs in series has not been set.

3 Devices that report this code

What does the F91 error code mean?

F91 on a Felicity unit indicates: The number of battery packs in series has not been set.. It is a fault-severity event that can appear on 3 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

F91 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.

T-REX-10KHP3G01Inverter↗ view on device

F91The number of battery packs in series has not been set.Fault

Description

Number of battery packs in series has not been set.

Recommended fix

Please set it correctly according to the number of battery packs used by the inverter.

Source:T-REX-10KHP3G01-Inverter-User-Guide.pdf · page 29

T-REX-10KLP3G01Inverter↗ view on device

F91The number of battery packs in series has not been set.Fault

Description

The number of battery packs in series has not been set.

Cause

The number of battery packs in series has not been set.

Recommended fix

Please set it correctly according to the number of battery packs used by the inverter.

Source:T-REX-10KLP3G01-Inverter-User-Guide.pdf · page 29

T-REX-50KHP3G01Inverter↗ view on device

F91PV hardware overcurrent fault.Fault

Description

PV current is too high, check string current.

Source:T-REX-50KHP3G01-user-manual-.pdf · page 49

Frequently asked about F91

What is the F91 error on Felicity?: F91 on a Felicity unit means: The number of battery packs in series has not been set.. It can appear on 3 different devices in the Felicity catalog. The cause and recommended fix are listed for each device on this page.
Can I clear the F91 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 F91 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.