Uniden UH810 Replacement Battery BP820 3.7V 1500mAh

Uniden UH810 / UH820S Series — 3.7V Li-ion Replacement Battery (BP820)

This is a 3.7V 1500mAh Li-ion replacement battery for the Uniden UH810, UH810S, and UH820S handheld two-way radios. It replaces OEM part numbers BP820 and BP-820. The pack slots directly into the existing battery compartment and connects to the radio's onboard charging and protection circuit.

• UH810, UH810S, and UH820S compatibility: All three models share the same 3.7V single-cell Li-ion platform, identical connector pinout, and the same BMS handshake protocol — one pack fits all three without any adaptor or modification.
• Bench tested on actual hardware: We cycled this pack through full charge and transmit-load discharge on the UH810 platform. The BMS held stable under PTT transmit current spikes and tripped correctly at the low-voltage cutoff threshold without latching into lockout.
• First insertion on the UH810 dock: If the dock LED flashes fault on first insertion, remove the pack, wipe the contact strip with a dry cloth, and reseat firmly. The UH810 charger requires a clean contact cycle to register the new BMS before it starts the charge sequence.

UH810 cutting out mid-transmission on a fresh BP820

A new Li-ion cell ships at storage voltage — typically 3.6–3.8V — not at full charge. When the UH810 draws transmit current from a cell at storage voltage, the internal voltage sags further under load. If it dips below the radio's transmit-enable threshold, the radio cuts TX mid-press. This is not a fault in the pack. Run one full charge cycle before first use and the transmit voltage headroom is restored.

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

The UH810 uses a simple voltage-threshold bar indicator — it reads resting cell voltage and maps it to bars. A new cell can read slightly lower resting voltage than a broken-in cell at the same state of charge, because cell impedance is higher before the first few cycles. After two or three full charge-discharge cycles, resting voltage stabilises and the bar display will align with actual charge level. If the indicator still reads low after three cycles, check that the dock contacts are clean and that the pack is reaching a full 4.2V terminal voltage at charge completion.