About this replacement
Kirisun DP770 / DP780 — 7.4V Li-ion Replacement Battery (KB-77B)
This is a 7.4V, 2000mAh Li-ion replacement battery for the Kirisun DP770 and DP780 portable two-way radios. It uses OEM part number KB-77B and fits directly into the standard battery bay on both models. Voltage and capacity match the original pack specification.
- DP770 and DP780 compatibility: Both models share the same 7.4V battery platform, connector pinout, and BMS handshake protocol. A single KB-77B pack serves either radio without modification.
- Bench tested on actual hardware: We cycled this pack under simulated PTT transmission loads. The BMS handled the transmit current spike without tripping overcurrent cutoff, and the cells held stable voltage across repeated PTT cycles.
- First insertion into the charger dock: If the dock shows a fault LED on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The Kirisun dock requires a clean contact cycle to complete the BMS handshake before charging begins.
Why the DP770 cuts out mid-transmission on a new KB-77B
A new Li-ion pack ships at storage voltage — typically 3.6–3.7V per cell, not full charge. When PTT is pressed, the radio draws peak transmit current. If the cells haven't completed a full charge cycle first, the BMS may interpret the voltage sag as an undervoltage event and cut output. This is not a faulty pack. Charge the battery fully before first operational use and the BMS will calibrate its threshold to the actual cell capacity.
Bar indicator shows one fewer bar than expected after inserting the KB-77B
The DP770 uses voltage-threshold bar indicators — each bar represents a voltage band, not a percentage calculated by a chip. A new pack at storage voltage sits in the lower threshold band and will display one or two bars even though the cells are not depleted. Place the battery in the charger dock until the charge LED goes green, then reinsert. The bar indicator should read full at or above 8.2V resting voltage.