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

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

The FNB-124LI is a 7.4V, 1100mAh lithium-polymer battery for the Horizon HX150 handheld two-way radio. It sits in the same footprint as the original pack and uses the same connector and BMS handshake the HX150 dock expects. Capacity figures come from the product data — 8.14Wh at the rated 1100mAh.

• HX150 platform fit: The HX150 uses a voltage rail and BMS communication protocol locked to the FNB-124LI form factor. Swapping to an off-spec pack trips the dock's acceptance check and blocks charging entirely — this replacement matches the exact parameters the radio's protection circuit requires.
• Bench tested on actual hardware: We cycled this pack through transmit-load draws consistent with a handheld PTT radio and monitored BMS cutoff behaviour. The protection circuit held within spec on both overcurrent and undervoltage thresholds during sustained TX bursts.
• First-insertion contact check: If the HX150 charger dock shows a fault LED on first insertion, remove the pack and wipe the gold contact strip with a dry cloth before reseating. The dock runs a BMS handshake on insertion, and any contamination on the contacts causes it to reject the pack before charging begins.

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

A fresh lithium-polymer cell ships at storage voltage — typically around 3.7V to 3.8V per cell, not the 4.2V full-charge ceiling. When the HX150 keys up to transmit, current draw spikes sharply. If the pack hasn't completed a full charge cycle first, the BMS reads that spike against a lower state-of-charge and triggers an overcurrent cutoff. The radio drops out, not because the battery is faulty, but because the protection circuit is doing exactly what it should. Charge the pack to full before first field use — the dock green LED confirms completion.

Bar indicator showing one fewer bar than expected after fitting the FNB-124LI

The HX150 uses a voltage-threshold bar indicator, not a capacity-counting chip. At storage voltage, the pack sits below the threshold the radio maps to a full bar display, so one bar appears missing even on a fresh cell. This is not a defect in the replacement pack. Run a full charge cycle through the dock until the green LED confirms completion — the bar indicator will reflect the correct voltage level once the cell reaches 8.4V total pack voltage.