Yaesu FNB-V86LI VX-820 Replacement Battery 7.2V 2600mAh

Yaesu VX-820 / VX-821 / VX-824 / VX-829 — 7.2V Li-ion Replacement Battery (FNB-V86LI / FNB-V87LI)

This is a 7.2V 2600mAh lithium-ion replacement battery for the Yaesu VX-820, VX-821, VX-824, and VX-829 portable transceivers. It replaces OEM part numbers FNB-V86LI and FNB-V87LI. The pack slots directly into the radio's battery compartment and engages the same contact array as the original.

• VX-820 series shared battery platform: The VX-820, VX-821, VX-824, and VX-829 all run the same 7.2V battery rail and use an identical four-contact connector with the same BMS handshake protocol — one pack covers the full series without modification.
• Bench tested on actual hardware: We cycled this pack through PTT transmit loads on the VX-820 and confirmed the BMS held steady through repeated high-current spikes without tripping into overcurrent lockout. Charge acceptance was clean on the standard desktop charger from the first cycle.
• First insertion into the charger dock: If the dock shows a fault LED on first insertion, remove the pack and wipe the gold contact strip with a dry cloth before reseating. The VX-series charger requires a clean contact cycle to complete the BMS handshake before it will begin charging.

Why the VX-820 cuts out mid-transmission on a new FNB-V86LI

A new cell ships at storage voltage — typically around 3.6–3.7V per cell — not at full charge. When you key up on a full-power transmission, the radio draws a sharp current spike that can push the BMS into a momentary undervoltage trip if the pack hasn't been charged first. The radio goes silent mid-PTT, and the display may flicker before recovering. Charge the pack fully before first field use and the BMS will have enough headroom to absorb that transmit surge without tripping.

Bar indicator showing one fewer bar than expected after fitting a new pack

The VX-820 reads battery level from raw terminal voltage, not a charge counter. A new pack at storage voltage reads lower than a freshly charged one, so the radio displays one fewer bar even though the cells are healthy. This is not a fault with the pack. Charge the battery fully in the desktop dock, let it cool for ten minutes, then reinsert — the indicator should show all bars at a resting voltage of approximately 8.2–8.4V.