Vertex Standard FNB-V105Li HX280S Replacement Battery 7.4V 1800mAh

Vertex Standard HX280S Series — 7.4V Li-ion Replacement Battery (FNB-V105Li)

This is a 7.4V, 1800mAh Li-ion replacement battery for the Vertex Standard HX280S, HX280, HX280E, and HX380 handheld transceivers. It replaces OEM part FNB-V105Li. The battery slots directly into the radio's battery compartment and communicates with the dock via the same contact configuration as the original pack.

• HX280S, HX280, HX280E, HX380 compatibility: These four models share the same battery bay dimensions, contact layout, and 7.4V voltage rail, which is why a single pack services all four. The BMS in this cell matches the charge-acceptance handshake the Vertex Standard dock expects at initial insertion.
• Bench tested on actual hardware: We ran this pack through charge cycles on the Vertex Standard dock and confirmed the BMS holds cutoff cleanly under transmit current spikes. The pack did not trigger overcurrent lockout during back-to-back PTT draws at full RF output.
• First insertion on the Vertex dock: If the dock LED shows a fault on first insertion, remove the battery and wipe the gold contact strip with a dry cloth before reseating. The Vertex Standard charging platform requires a clean contact cycle to register the new BMS handshake before it will begin charging.

Why the HX280S drops to reduced TX power mid-shift on a fresh battery

New Li-ion cells ship at storage voltage — typically 3.6–3.8V per cell, not full charge. At storage voltage, the pack cannot sustain the current demanded by sustained RF output, so the radio's power management steps down TX power to protect the final stage amplifier. This is not a faulty battery. A full charge cycle before the first shift brings both cells to 4.2V each, restoring full RF output headroom. The symptom disappears after one complete charge.

Bar indicator showing one fewer bar than expected after fitting the FNB-V105Li

The HX280S uses voltage-threshold bar indicators — each bar corresponds to a specific voltage band, not a fuel-gauge percentage. A new pack at storage voltage sits below the threshold for the top bar, so the display shows one bar low even though the cell is healthy. Charge the battery fully in the dock until the charge LED goes green. Once the pack reaches 8.4V at rest, the indicator will display the correct bar count on next power-on.