Motorola CP040 Compatible Battery 7.5V 2600mAh PMNN4254

Motorola CP040 / CP140 Series — 7.5V Li-ion Replacement Battery (PMNN4254AR)

This 7.5V, 2600mAh lithium-ion battery replaces the original pack on Motorola CP-series portable two-way radios. It fits the CP040, CP100, CP100D, and CP140, along with 28 additional CP-series models that share the same voltage rail and connector format. Cross-references include PMNN4254AR, NNTN4851, PMNN4081AR, and over 30 other Motorola OEM part numbers.

• CP-series platform fit: These models share a common 7.5V architecture, identical battery bay dimensions, and the same BMS handshake protocol — which is why one pack covers the full range without a firmware or connector conflict.
• Bench tested on actual hardware: We cycled this pack through PTT transmit loads on the CP040. The BMS handled the current spike on key-up without tripping, and the charger dock accepted the new pack without a fault LED after a clean contact seating.
• First insertion into the charger dock: If the dock shows a fault LED on the first seating, remove the pack, 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 charging begins.

Why the CP040 drops to reduced TX power mid-shift on a new battery

A new cell ships at storage voltage — typically around 3.7V per cell, not full charge. Under sustained RF output, the radio draws peak current and the BMS reads the resulting voltage sag as a low-battery condition. The radio responds by stepping down transmit power to protect the pack. A full charge cycle before the first shift eliminates this — the cells need to reach operational voltage before the radio can sustain full TX output.

Bar indicator showing fewer bars than expected after fitting a new pack

The CP040 uses a voltage-threshold bar indicator, not a fuel gauge chip. A new cell at storage voltage reads lower than a freshly charged pack, so the radio displays one or two bars even though the battery is not depleted. This is not a fault with the battery. Charge the pack fully in the dock — once cell voltage climbs above the top threshold, the indicator will display correctly.