About this replacement
Motorola CP250 / GP300 Series — 7.2V Ni-MH Replacement Battery (HNN8133C)
This is a 7.2V, 1800mAh nickel-metal hydride replacement battery for the Motorola CP250, CP450, CP450LS, and GP300 series portable two-way radios. It cross-references OEM part numbers HNN8133C, HNN9628A, PMNN4005, and several others in the same family. Voltage and cell count match the original pack exactly.
- CP250 / CP450 / GP300 platform fit: These radios share the same battery bay dimensions, six-cell NiMH voltage rail, and contact pin layout. The BMS handshake on the Motorola analog platform is contact-based — no digital authentication token is required, so swapping packs does not trigger a firmware rejection.
- Bench tested on actual hardware: We cycled this pack through full charge and a sustained PTT-draw test on a CP250 unit. The BMS held voltage above the radio's low-battery cutoff threshold across the full discharge curve without false low-battery alerts.
- First insertion into the charger dock: If the dock LED flashes fault on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. Motorola single-unit drop-in chargers require a clean contact cycle before they will initiate the trickle pre-charge on a new NiMH pack at storage voltage.
Why the CP250 cuts out mid-transmission on a freshly inserted pack
The CP250 draws a sharp current spike the moment PTT is pressed — transmit current can exceed 1.5A for the RF stage alone. A new NiMH pack sitting at storage voltage (typically 7.0–7.1V) has higher internal impedance than a fully charged cell. That impedance causes a momentary voltage sag that trips the radio's low-voltage protection before the pack has warmed up through even one charge cycle. Charge the pack fully in the dock before first use in the field. After two full charge-discharge cycles, cell impedance drops and the sag under TX load normalises.
Bar indicator showing one fewer bar than expected on a new pack
The CP250 and GP300 use a simple voltage-threshold bar display — each bar corresponds to a voltage band, not a calibrated capacity reading. A new NiMH pack ships at roughly 60–70% state of charge to comply with transport regulations, so the resting voltage sits in the two-bar band rather than three. This is not a fault. Put the pack through a full charge cycle in the Motorola drop-in or multi-unit charger. After charge completes and the dock LED goes solid green, resting voltage will read in the full three-bar range at approximately 7.5–7.6V.