About this replacement
Motorola Radius P1225 / P50 / P1225 LS — 7.5V Ni-MH Replacement Battery (HNN9049)
This is a 7.5V, 2000mAh Ni-MH battery for the Motorola Radius P1225, Radius P50, and Radius P1225 LS portable two-way radios. It replaces OEM part numbers HNN9049, HNN9049A, HNN9049B, and HNN9049H. The pack slots into the same battery bay and connects through the same three-contact interface as the original.
- Radius P1225, P50, and P1225 LS platform: These three radios share the same battery form factor, voltage rail, and contact pinout. A single pack covers all three because Motorola used the same battery bay design across the P-series lineup — the BMS handshake and charging protocol are identical on each.
- Bench tested on actual hardware: We cycled this pack through full charge and discharge on P1225 hardware. The BMS held the voltage rail steady through PTT transmit bursts without triggering overcurrent cutoff, and the charger dock accepted the pack on the first insertion without a fault LED.
- First insertion on Motorola charger dock: If the dock LED shows fault on the very first seating, remove the pack and wipe the three gold contacts with a dry cloth before reseating. The P1225 charger checks contact resistance before initiating charge — even slight contamination from packaging can block the handshake cycle.
Why the Radius P1225 cuts out mid-transmission on a new pack
Ni-MH cells ship at storage voltage — typically 1.1–1.2V per cell — not at full charge. When the P1225 keys up to transmit, it draws a sharp current spike that can pull the pack voltage below the BMS cutoff threshold if the cells haven't been fully charged first. The radio interprets this voltage drop as a depleted pack and cuts TX power or drops the transmission entirely. Running one complete charge cycle before first use brings all six cells to operating voltage and eliminates this behaviour.
Bar indicator shows one fewer bar than expected after charging
The P1225 uses a simple voltage-threshold system to display charge bars — each bar corresponds to a specific pack voltage range. A new Ni-MH pack that hasn't been fully cycled yet will rest at a slightly lower open-circuit voltage than a broken-in pack, which can push the reading one bar below where it should land. This is a cell conditioning issue, not a faulty battery. Run two full charge-discharge cycles and the resting voltage will stabilise — the bar indicator should then read accurately at 7.5V full charge.