About this replacement
Motorola CT150 / CT250 / CT450 Series — 7.4V Li-ion Replacement Battery (HMNN4151)
This is a 7.4V, 2700mAh Li-ion battery pack for the Motorola CT150, CT250, CT450, and CT450LS two-way radios. It replaces a wide range of Motorola OEM part numbers including HMNN4151, PMNN4018, HNN9008A, and over 35 additional cross-references. The pack slots into the same housing footprint and uses the same connector as the original.
- CT150 / CT250 / CT450 platform fit: These models share the same battery housing format, contact layout, and BMS handshake protocol. A single cell configuration at 7.4V covers the transmit voltage rail across the whole family — no adapter or modification needed.
- Bench tested on actual hardware: We ran this pack through full charge-discharge cycles on a CT450 dock. The BMS handled PTT transmit current spikes without tripping to protection mode, and the charger dock advanced from amber to green charge-complete without fault events.
- First insertion on a Motorola dock: If the dock shows a fault LED on the first seating, remove the pack and wipe the gold contact strip with a dry cloth before reseating. The CT-series charger runs a contact resistance check before initiating the BMS handshake — any residue from packaging can break that cycle.
Why the CT450 drops to reduced TX power mid-shift on a new pack
New Li-ion cells ship at storage voltage — typically around 3.7V per cell, not full charge. When the radio draws sustained RF output, the voltage sags below the threshold the CT450's power management circuit uses to maintain full transmit power. The radio reads this as a low-battery condition and steps down TX output to protect the final stage. A full charge cycle before the first shift eliminates this — the pack needs to reach 8.4V across both cells before it can hold voltage steady under RF load.
Bar indicator reads one bar lower than expected after installing a new HMNN4151
The CT-series bar indicator is a voltage-threshold display, not a capacity meter. At storage voltage, the pack sits in the one- or two-bar zone even though the cells are healthy and fully functional. This is not a fault with the pack. Charge the battery to completion on the dock — once resting voltage hits approximately 8.2V or above, the indicator will reflect the correct charge state on next power-on.