Motorola CT150 Replacement Battery PMNN4017 7.5V 2500mAh

My CT250 drops to low transmit power partway through a shift even though the battery was fully charged at the start — what's happening?

Sustained RF output puts a continuous current load on the pack, and Ni-MH cells lose voltage more steeply under that load as they discharge past roughly 60% capacity. When pack voltage sags under the radio's TX power threshold, the CT250 steps down transmit power automatically rather than cutting out entirely. This is a voltage sag failure, not a faulty cell — the pack is simply reaching the point where it can no longer support full RF output. Swap to a freshly charged pack mid-shift for high-transmission environments, or check the resting voltage after a charge: a healthy pack should read at least 8.4V off the charger.

The charger dock LED blinks amber and never clears after inserting this battery — the radio charges fine in the same dock with the old pack.

The dock checks pack voltage before starting a charge cycle, and a new Ni-MH pack shipped at storage voltage can sit below the dock's acceptance threshold — typically around 6.0V for a 7.5V pack. The dock reads this as a fault rather than a dischargeable pack and refuses to begin. Remove the battery, short-circuit the contacts briefly with a resistive load (a 10-ohm resistor across the terminals for 30 seconds works), then reinsert — this nudges the cell voltage just enough for the dock's BMS handshake to accept it. Alternatively, some CT-series chargers have a recovery/refresh mode; press and hold the charge button for five seconds on insertion to trigger it.

After this battery sat unused in a drawer for a few months, the CT150 won't recognise it at all — radio stays off on insertion.

Ni-MH cells in extended storage self-discharge to the point where pack voltage can drop below the radio's minimum power-on threshold, roughly 5.5–6.0V. At that level the BMS may also lock the pack to prevent the radio from attempting to draw current from critically low cells. Place the pack directly in the charger dock — not the radio — and leave it for a full charge cycle of at least three hours. If the dock accepts it and completes the cycle, pack voltage will recover to operating range and the CT150 will power on normally; check for a green LED at end-of-charge before reinserting into the radio.