About this replacement
Motorola APX1000 / APX2000 Series — 7.4V Li-ion Replacement Battery (PMNN4406)
This is a 7.4V, 3200mAh Li-ion battery for the Motorola APX1000, APX2000, APX3000, and APX4000 portable digital radios. It replaces OEM part numbers PMNN4406, PMNN4409, PMNN4412, PMNN4448, PMNN4490, PMNN4491, PMNN4493, PMNN4543, and PMNN4544, among others. These radios are used in public safety and professional field operations where battery failure is not an option.
- APX series compatibility: The APX1000 through APX4000 share the same 7.4V battery platform, connector pinout, and BMS handshake protocol. One battery format covers the full entry-to-mid tier APX lineup, which is why this single part replaces such a broad OEM number range.
- Bench tested on actual hardware: We ran this pack in an APX1000 dock and cycled it through full PTT load draws. The BMS handled transmit-surge current correctly and the charger dock accepted the BMS handshake without fault LED on the first insertion.
- First insertion on the dock: If the charger shows a fault LED on first seating, remove the battery, wipe the gold contact strip with a dry cloth, and reseat firmly. The APX dock requires a clean contact cycle to complete the BMS handshake before it begins charging.
Why the APX1000 cuts out mid-transmission on a new battery
A new Li-ion cell ships at storage voltage — typically around 3.7V per cell, not the 4.2V full-charge ceiling. When the APX1000 keys up to transmit, it draws a sharp current spike that can push a low-state cell below the BMS undervoltage cutoff threshold. The BMS trips, the radio drops off-air, and the user assumes the battery is faulty. It is not — charge the pack fully in the dock before the first use shift and the cutout will not recur.
Bar indicator showing one fewer bar than expected after a full charge cycle
The APX series uses a simple voltage-threshold bar indicator, not a fuel gauge chip. A new cell fresh off its first charge cycle may rest at a slightly lower open-circuit voltage than a conditioned pack, pushing it one threshold below the top bar. Run two to three full charge-discharge cycles and the resting voltage settles correctly. If the indicator still reads low after three cycles, check that the dock contacts are clean and that the charge completed fully rather than ending on a fault.