About this replacement
Motorola CP040 / CP140 Series — 7.5V Ni-MH Replacement Battery (MNN4254AR)
This is a 7.5V, 2500mAh Ni-MH replacement battery for the Motorola CP040, CP100, CP100D, CP140, and over 28 compatible models in the CP series. It cross-references OEM part numbers including MNN4254AR, NNTN4496, PMNN4081, PMNN4082, and PMNN4404ART. The cell chemistry and connector match the original Motorola spec for this radio family.
- CP series compatibility: The CP040 through CP140 range shares a common battery footprint, contact layout, and 7.5V operating rail. These radios use the same BMS handshake protocol, which is why a single pack covers the full model spread without modification.
- Bench tested on actual hardware: We cycled this pack through full charge and load discharge on a CP140 body. The BMS accepted the charger handshake on first insertion, held voltage above the radio's low-battery threshold through the discharge curve, and showed no premature cutoff under PTT load.
- First insertion contact check: If the charger dock shows a fault LED when you first seat this pack, remove it, wipe the gold contact strip with a dry cloth, and reseat firmly. The CP series charger requires a clean contact cycle to complete the BMS acceptance check before it begins charging.
Why the CP040 cuts out mid-transmission on a freshly charged battery
Pressing PTT draws a short, sharp current spike — typically 1.5–2A — as the RF output stage powers up. Ni-MH cells that have sat at storage voltage for several months show elevated internal impedance, which causes a brief voltage sag at that spike. If the sag drops the rail below 6.0V for even a fraction of a second, the radio's undervoltage circuit trips and cuts TX. Running two to three full charge-discharge cycles through the new pack lowers cell impedance and eliminates the sag.
Bar indicator showing one fewer bar than expected after a full charge
The CP series uses a simple voltage-threshold indicator — each bar maps to a voltage band, not a capacity percentage. A new Ni-MH pack fresh from storage sits at approximately 7.2V resting, which can read one bar low until the cells have been fully charged and rested. Charge the pack to completion, let it rest off the dock for 15 minutes, then reinsert it into the radio. The resting open-circuit voltage should read at or above 7.4V and the indicator will reflect that correctly.