Standard Horizon HX150 FNB-124LI Replacement Battery 7.4V 1100mAh

Standard Horizon HX150 — 7.4V Li-Polymer Replacement Battery (FNB-124LI)

This 7.4V, 1100mAh lithium-polymer battery replaces the FNB-124LI in the Standard Horizon HX150 handheld VHF marine transceiver. The HX150 is a compact marine radio used for voice communication and emergency signalling on the water. This pack slots into the same battery compartment and connects to the same BMS handshake circuit as the original.

• HX150 platform fit: The HX150 uses a 7.4V two-cell lithium-polymer configuration with a specific connector pinout and BMS communication line. Any replacement pack must match this voltage rail exactly — a mismatched BMS handshake will prevent the charger dock from initiating a charge cycle at all.
• Bench tested on actual hardware: We ran this pack through the HX150 charge dock and confirmed the BMS handshake completed correctly. The dock moved from fault state to active charge without manual reset, and the cell held voltage under simulated PTT transmit-current draw.
• Marine contact maintenance: Saltwater air accelerates oxidation on the gold contact strip faster than on land radios. If the dock shows a fault LED after a day on the water, wipe the contacts on both the battery and the dock with a dry cloth before reseating — salt film breaks the contact cycle the BMS needs to begin charging.

Why the HX150 cuts out mid-transmission on a new FNB-124LI

A new lithium-polymer cell ships at storage voltage — typically around 3.7V to 3.8V per cell, not full charge. When the HX150 keys up to transmit, the RF output stage draws a sharp current spike. If the cell is at storage voltage, that spike can pull the pack below the BMS low-voltage cutoff threshold, triggering an immediate shutdown. This is a BMS protection event, not a faulty pack. Run one full charge cycle before the first transmission test and the cutout will not repeat.

Bar indicator showing one fewer bar than expected after a full charge

The HX150 reads battery level using voltage thresholds — each bar on the display corresponds to a voltage band. A new cell that has only completed one charge cycle may settle at a resting voltage slightly below the top threshold once the surface charge dissipates, causing the indicator to show one bar short. This is not a capacity fault. Run two full charge-discharge cycles and the resting voltage will stabilise above 8.2V, bringing the indicator into the expected range.