Stabo FT553444P-2S Freecomm 600 Replacement Battery 3.7V 800mAh

Stabo freecomm 600 Set — 3.7V Li-ion Replacement Battery (FT553444P-2S)

This 3.7V 800mAh Li-ion cell replaces the original FT553444P-2S pack in the Stabo freecomm 600 Set, PMR 446, 20640, and Freecomm 850 two-way radios. It fits the original battery bay without modification and uses the same connector pinout as the factory cell. Voltage and physical dimensions — 46.35 × 31.94 × 6.31mm — match the OEM spec exactly.

• freecomm 600 Set / PMR 446 / 20640 / Freecomm 850 platform: These four models share the same 3.7V single-cell architecture, battery bay dimensions, and contact strip arrangement. The FT553444P-2S part number covers all four because the BMS handshake threshold and connector layout are identical across the range.
• Bench tested on actual hardware: We cycled this cell under simulated PTT load — the BMS held the output rail steady through repeated transmit bursts and tripped correctly at the low-voltage cutoff threshold without latching into lockout on recovery.
• Contact strip seating on first insertion: PMR 446-class radios with sliding battery doors apply less clamping force than screw-retained packs. If the radio powers on briefly then cuts off, press the battery door firmly until you hear the latch click — an unseated contact strip causes intermittent voltage drops the BMS reads as a fault.

Why the freecomm 600 cuts out mid-transmission on a new battery

Pressing PTT draws a short current spike as the radio switches from standby to full RF output. A new cell shipped at storage voltage — typically around 3.6–3.7V — has less headroom than a fully charged pack, so the transmit spike can momentarily pull the rail below the BMS undervoltage threshold. The BMS disconnects the output to protect the cell, which the radio reads as a power failure. A full charge before first use brings the cell to 4.2V and gives the BMS adequate headroom to absorb that transmit spike without tripping.

Bar indicator showing one fewer bar than expected after fitting the FT553444P-2S

The freecomm 600 series uses a simple voltage-threshold bar display — each bar corresponds to a fixed voltage band, not a calculated capacity percentage. A cell at storage voltage sits in the lower threshold band and shows one or two bars even when the cell is healthy. Charge the pack fully to 4.2V in the original dock, then power the radio on. The bar display will read the higher voltage band and show the correct number of bars.