HYT TC-700 BL1703 Replacement Battery 7.4V 3350mAh

HYT TC-700 / TC-780 Series — 7.4V Li-ion Replacement Battery (BL1703)

This 7.4V, 3350mAh lithium-ion battery replaces the OEM pack on the HYT TC-700, TC-700U, TC-780, and TC-780M portable two-way radios. It matches the original BL1703, BL1703Li, BL2102, BH1801, and BL-2102Li part numbers. Physical dimensions are 110.00 × 56.30 × 23.50mm — same footprint as the factory pack.

• TC-700 and TC-780 platform fit: Both radio lines share the same battery bay geometry, contact layout, and 7.4V supply rail. The BMS handshake protocol is identical across the TC-700U and TC-780M variants, so one pack covers the full family without modification.
• Bench tested on actual hardware: We ran this pack through full charge and discharge cycles on a TC-780M dock. The BMS responded correctly to transmit current spikes, held the protection threshold without nuisance tripping, and accepted a full charge on the first dock cycle.
• First dock insertion on the TC-700 charger: If the charger LED shows a fault on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The TC-700 charger requires a clean contact cycle to complete the BMS handshake before it begins charging.

Why the TC-700 cuts out mid-transmission on a new BL1703 pack

A new cell ships at storage voltage — typically around 3.7V per cell, or roughly 7.4V total. When PTT is pressed, the transmit current surge can pull the pack below the BMS overcurrent threshold before a full charge cycle has conditioned the cells. The BMS interprets the spike as a fault and disconnects the output, which kills the transmission. A single full charge cycle before field use stabilises the cell impedance and prevents this trip.

Bar indicator showing one fewer bar than expected on a freshly charged pack

The TC-700 and TC-780 use a voltage-threshold bar indicator — each bar corresponds to a fixed voltage band, not a percentage from a fuel gauge chip. A new pack coming off its first charge may rest at a slightly lower open-circuit voltage than a broken-in cell, pushing the reading one threshold below full. This is not a capacity fault. After two to three full charge and discharge cycles, the resting voltage stabilises and the indicator aligns correctly with the 7.4V full-charge threshold.