Vertex Standard VX-820 Compatible Battery FNB-V86LI 7.2V 2600mAh

Vertex Standard VX-820 / VX-824 Series — 7.2V Li-ion Replacement Battery (FNB-V86LI)

This is a 7.2V, 2600mAh lithium-ion battery for the Vertex Standard VX-820, VX-821, VX-824, and VX-829 portable two-way radios. It replaces OEM part numbers FNB-V86LI, FNB-V87LI, and FNB-V86. The battery mounts and latches using the same housing geometry as the original pack.

• VX-820 series platform fit: The VX-820, VX-821, VX-824, and VX-829 share the same 7.2V rail, battery latch, and contact pin layout. One pack covers all four models because Vertex Standard held that hardware constant across the series.
• Bench tested on actual hardware: We ran this pack through a full charge cycle and verified the BMS handshake with the standard Vertex charger dock. The protection circuit tripped correctly at the expected current thresholds during transmit-load simulation.
• First insertion into the charger dock: If the dock shows a fault LED on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The Vertex platform requires a clean contact cycle before the dock accepts a new BMS and begins charging.

Why the VX-820 cuts out mid-transmission on a freshly inserted battery

Pressing PTT on the VX-820 draws a sharp current spike as the RF output stage ramps to full power. If the battery shipped at storage voltage — typically 3.6–3.7V per cell — the BMS may read that spike as an overcurrent event and momentarily cut the output. This is not a faulty pack. Placing the battery in the charger for at least one full charge cycle before use brings cell voltage up to the threshold where the BMS handles transmit spikes without tripping.

Bar indicator showing one fewer bar than expected on a new pack

The VX-820 reads battery level from cell voltage alone — it has no capacity-tracking circuit. A new pack at storage voltage sits below the top voltage threshold, so the radio displays one bar fewer than a fully charged cell. This is a voltage reading, not a sign the pack is weak or undersized. Charge the battery fully in the dock first; once cell voltage reaches approximately 8.4V, the indicator will show correctly.