HYT TC-700 Replacement Battery BL1703 7.4V 2100mAh

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

This 7.4V, 2100mAh Li-ion battery replaces the HYT BL1703 pack used in the TC-700, TC-700U, TC-780, and TC-780M series handheld radios. These radios are widely used in public safety, security, and commercial operations where radio contact cannot drop. Voltage and capacity match the original HYT specification exactly.

• TC-700 and TC-780 platform fit: Both series share the same battery bay geometry, contact pin layout, and 7.4V BMS handshake protocol — one pack covers the full range. The BL1703, BL1703Li, BL2102, BH1801, and BL-2102Li part numbers are all cross-compatible within this platform.
• Bench tested on actual hardware: We cycled this pack through PTT transmit loads on a TC-780M dock. The BMS held the voltage rail steady through sustained transmit bursts and released cleanly after each draw spike without triggering overcurrent lockout.
• First insertion into the charger dock: If the dock LED shows a fault on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The HYT dock runs a contact-verification step before accepting a new BMS handshake — a single residue smear is enough to block it.

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

New Li-ion cells ship at storage voltage — typically around 3.6–3.7V per cell, or roughly 7.2V across the pack. When PTT is pressed, transmit current demand spikes sharply, and a pack sitting at storage voltage has less headroom before the BMS reads undervoltage and trips. The radio cuts out not because the pack is faulty, but because the BMS is protecting cells that haven't been charged to operating voltage yet. Charge the pack fully before the first shift — the cutout behaviour disappears once the pack is above 8.0V.

Bar indicator showing one fewer bar than expected on a new BL1703

The TC-700 and TC-780 use a simple voltage-threshold bar display — each bar maps to a fixed voltage window. A new pack at storage voltage sits at the lower end of the scale, so the radio correctly shows one or two bars even though the pack is not depleted. This is not a capacity fault. Place the pack in the dock, charge to green, and the bar indicator will read full. If it still reads low after a full charge cycle, measure pack voltage at the contacts — a healthy charged pack should read 8.3–8.4V.