About this replacement
HYT TC600 Series — 7.4V Li-ion Replacement Battery (BL1203)
This is a 7.4V, 1250mAh Li-ion replacement battery for the HYT TC600 two-way radio. It fits the TC600 and TC-600 variants and uses OEM part number BL1203. Capacity figure is taken directly from the product specification — 9.25Wh.
- TC600 and TC-600 platform fit: Both model designations share the same battery bay geometry, connector pinout, and BMS handshake protocol. A single BL1203-spec pack covers both without modification or adapter.
- Bench tested on actual hardware: We cycled this pack through transmit loads on the TC600 platform. The BMS held steady under PTT current spikes and recovered cleanly to float voltage after each discharge cycle — no false cutoff events recorded.
- Dock insertion on first use: If the charger dock shows a fault LED on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The TC600 dock requires a clean contact cycle to complete the BMS handshake before it will begin charging.
Why the TC600 cuts out mid-transmission on a freshly inserted BL1203
The TC600 draws a sharp current spike the moment PTT is pressed — transmit current can momentarily exceed the standby draw by several times. A new Li-ion cell shipped at storage voltage (typically 3.6–3.7V per cell) has higher internal impedance than a fully charged cell. Under that spike, the BMS reads the voltage dip as an overcurrent event and trips the protection circuit. The fix is straightforward: charge the pack to full before the first transmit use. A fully charged cell at 4.2V per cell handles the PTT spike without triggering BMS cutoff.
Bar indicator showing one fewer bar than expected after fitting the BL1203
The TC600 uses a simple voltage-threshold bar indicator — each bar maps to a voltage band, not a percentage reading from a fuel gauge chip. A new pack at storage voltage sits in the lower threshold bands, so the display shows one or two bars even though the cell is not depleted. This is not a fault with the replacement pack. Charge the battery fully and the indicator will step up to the top bar once the cell reaches its charged resting voltage of around 8.3–8.4V across the pack.