HYT BL1703 TC-700 Replacement Battery 7.4V 1600mAh

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

This is a 7.4V, 1600mAh Li-ion battery for the HYT TC-700, TC-700U, TC-780, and TC-780M two-way radios. It also cross-references OEM part numbers BL1703Li, BL2102, BH1801, and BL2102Li. If your current pack no longer holds charge through a full shift, this is the direct swap.

• TC-700 and TC-780 platform fit: Both series run the same 7.4V power rail, share an identical battery bay connector, and use the same BMS handshake protocol — which is why a single pack covers the full lineup without modification.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a TC-700 body, confirmed the BMS handshake completed correctly with the HYT charger dock, and verified that the transmit-current spike on PTT did not trip overcurrent cutoff.
• First insertion into the HYT dock: If the dock LED flashes fault on first seating, remove the pack and wipe the gold contact strip with a dry cloth before reseating. The HYT charger checks contact resistance as part of its BMS handshake cycle, and even light surface oxidation from storage can cause a rejection on the first attempt.

Why the TC-700 cuts out mid-transmission on a freshly installed battery

The TC-700 draws significantly more current during transmit than during standby or receive. A new pack shipped at storage voltage — typically around 3.7V per cell — has higher internal resistance than a fully charged cell. When PTT is pressed, that resistance causes a brief voltage sag. If the sag drops below the BMS undervoltage threshold, the pack cuts out before the transmission completes. The fix is straightforward: charge the pack fully before the first use on-radio, which brings cell voltage to 4.2V per cell and lowers resistance enough to handle the transmit surge cleanly.

Bar indicator showing one fewer bar than expected after installing this pack

The TC-700 and TC-780 use a voltage-threshold bar indicator — not a fuel gauge chip. Each bar corresponds to a voltage band, and a new cell at storage voltage (roughly 3.7–3.8V per cell) sits in the two-bar zone even though the pack is not depleted. This is normal cell behaviour, not a capacity fault. Charge the pack fully in the HYT dock until the green LED confirms completion, then insert it into the radio — the indicator will read correctly at full charge.