About this replacement
Motorola CP040 / CP140 Series — 7.5V Li-ion Replacement Battery (MNN4254AR)
This is a 7.5V 1800mAh Li-ion battery for the Motorola CP040, CP100, CP100D, CP140, and related CP-series two-way radios. It replaces a long list of Motorola OEM part numbers including MNN4254AR, NNTN4851, PMNN4081, PMNN4082, and PMNN4251, among others. The battery uses the same connector and BMS pinout as the original pack.
- CP040 / CP100 / CP140 platform fit: These models share the same battery bay dimensions, contact strip layout, and 7.5V supply rail. The dock charger reads the BMS data line on all three, so a single pack serves the whole family without any adapter or modification.
- Bench tested on actual hardware: We cycled this pack through full charge and discharge on a CP140 test unit. The BMS accepted the dock handshake on first insertion, held voltage above 7.0V through sustained draw, and tripped overcurrent protection cleanly under a simulated high-current PTT burst — then reset without fault.
- First-insertion contact check on CP-series docks: If the dock LED flashes fault on first seating, pull the pack out, wipe the gold contact strip with a dry cloth, and reseat firmly. The CP-series dock requires a clean contact cycle to complete the BMS handshake before it will begin charging.
Why the CP040 cuts out mid-transmission on a new battery
When PTT is pressed, the transmitter pulls a short current spike — typically 1.5A to 2A on the CP040 — that the BMS must pass without tripping. A pack with weak cells or a conservative BMS threshold will cut the output rail during that spike, dropping the transmission. This battery's BMS is set to handle the full CP040 TX current without nuisance tripping. If cutouts still happen after fitting this pack, check that the radio's RF power setting is not stuck on high from a previous configuration.
Bar indicator showing one fewer bar than expected on a new pack
The CP040 uses voltage thresholds to drive its bar display — there is no fuel gauge chip. A new cell ships at storage voltage, typically around 3.7V per cell, which reads lower than a freshly charged pack. The radio sees that voltage and displays one or two bars even though the pack is not depleted. Run a full charge cycle first; once the pack reaches 8.4V at the terminals, the bar indicator will show full.