About this replacement
Kirisun PT-3300 / PT-3500 / PT-3800 — 7.4V Li-ion Replacement Battery (KB-33L)
The KB-33L is a 7.4V, 1200mAh Li-ion battery for the Kirisun PT-3300, PT-3500, and PT-3800 portable two-way radios. It matches the original pack's voltage rail and connector footprint. Capacity is 1200mAh (8.88Wh), consistent with the factory specification for this platform.
- PT-3300 / PT-3500 / PT-3800 platform fit: All three models run the same 7.4V dual-cell configuration with an identical contact layout and BMS handshake protocol. A single battery variant covers the full range without any modification.
- Bench tested on actual hardware: We cycled this pack through transmit loads on the PT-3300 chassis. The BMS held stable across repeated PTT bursts and did not trigger overcurrent cutoff under normal push-to-talk draw.
- First insertion contact check: 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 Kirisun dock requires a clean contact cycle to complete the BMS handshake before charging begins.
Why the PT-3300 cuts out mid-transmission on a freshly inserted KB-33L
New Li-ion cells ship at storage voltage — typically 3.6–3.7V per cell, placing the pack around 7.2V at rest. When PTT is pressed, transmit current spikes and the voltage momentarily dips below the BMS cutoff threshold. The radio interrupts transmission and may appear to restart. A full charge cycle before field use brings both cells to 4.2V each and eliminates this behaviour entirely.
Bar indicator showing one fewer bar than expected after fitting the KB-33L
The PT-3300 series uses a voltage-threshold bar indicator — it reads pack voltage directly and maps it to bar levels. A new pack at storage voltage reads lower than a fully charged pack, so the display shows one or two bars instead of a full stack. This is not a fault with the cell. Charge the battery fully in the dock until the LED turns green, then reinsert — the indicator will reflect the correct charge state at 8.4V.