Icom BP-307 IC-705 Compatible Battery 7.4V 3300mAh

Icom IC-705 / ID-51E / ID-52E Series — 7.4V Li-ion Replacement Battery (BP-307)

The BP-307 is a 7.4V 3300mAh Li-ion battery for the Icom IC-705 HF/VHF/UHF portable transceiver and the ID-31E, ID-51E, and ID-52E handheld series. It slots into the original battery bay and connects via the same multi-pin contact strip the OEM pack uses. Capacity figures come from the product data: 3300mAh / 24.42Wh.

• IC-705 and ID-5x series compatibility: These models share the same 7.4V two-cell architecture, BP-307 footprint, and BMS handshake protocol. The dock and radio both read pack state through the same contact arrangement, so one replacement cell works across the whole range without adapters or firmware changes.
• Bench tested on actual hardware: We ran the BP-307 through a full charge cycle in an Icom BC-202IP2 dock and monitored BMS response during simulated PTT transmit draws. The protection circuit handled the current spike at key-down without tripping into lockout, and the dock moved to charge-complete status cleanly.
• First-insertion contact cycle on the IC-705: If the BC-202IP2 dock flashes a fault LED on first insertion, remove the BP-307, wipe the gold contact strip with a dry cloth, and reseat it firmly. The IC-705 platform requires a clean contact cycle to complete the BMS handshake before the dock will begin charging.

IC-705 TX power drop during sustained SSB or digital mode operation

The IC-705 draws significantly more current during SSB and digital mode transmissions than during receive. A cell with elevated internal impedance — common in aged packs — causes voltage to sag under that load, and the radio's internal protection circuitry reduces TX output to stay within safe operating voltage. A fresh BP-307 at full charge presents lower cell impedance, so the voltage rail stays stable under key-down. If TX power still drops after a full charge cycle, confirm the dock reached charge-complete and the terminal voltage reads at or above 8.3V before operating.

Bar indicator showing one fewer bar than expected after inserting a new BP-307

New Li-ion cells ship at storage voltage — typically around 3.7V per cell — not at full charge. The IC-705 uses voltage-threshold bar indicators, so a pack at storage voltage will display fewer bars than a fully charged one, which is not a fault. Place the BP-307 in the dock and run a complete charge cycle before judging capacity. Once the dock signals charge-complete, the indicator should show full bars at the rated 8.4V terminal voltage.