About this replacement
Motorola CT150 / CT250 / CT450 Series — 7.2V Ni-MH Replacement Battery (HMNN4151)
This is a 7.2V, 2100mAh nickel-metal hydride battery for the Motorola CT150, CT250, CT450, and CT450LS portable two-way radios. It replaces a wide range of OEM part numbers including HMNN4151, HMNN4151AR, PMNN4017, PMNN4018, and HNN9008 variants. Drop the old pack out, seat this one in, and the radio powers on without configuration changes.
- CT150 / CT250 / CT450 platform fit: These models share the same battery bay geometry, contact pin layout, and 7.2V NiMH voltage rail. The BMS handshake across all variants uses the same threshold, so one pack covers the full range without adapter or modification.
- Bench tested on actual hardware: We cycled this pack through charge and discharge on the CT series dock. The BMS held the 7.2V rail steady under simulated transmit load and did not trigger a protection cutoff at normal PTT current draw.
- First-charge protocol on the CT dock: NiMH cells ship at a partial storage charge. Run the first full charge cycle in the Motorola dock without interruption — pulling the pack early on the first cycle can cause the dock to misread cell capacity on subsequent charges and display a premature full-charge LED.
Why the CT450 cuts out mid-transmission on a new HMNN4151 pack
NiMH cells fresh from storage sit between 1.0V and 1.1V per cell — below the voltage the radio expects under transmit load. When you key PTT, the radio draws a sharp current spike to drive the RF stage. If cell voltage sags below roughly 6.0V under that load, the radio's undervoltage protection trips and kills the transmission. This is not a fault with the pack. One or two full charge-discharge cycles on the Motorola dock brings the cells up to working voltage and the sag disappears.
CT150 bar indicator showing one bar on a fully charged new pack
The CT series reads voltage thresholds at rest to set the bar display — it does not track capacity directly. A new NiMH pack at storage voltage reads lower than a conditioned pack at the same state of charge, so the radio displays fewer bars even after the dock shows a full-charge LED. Complete one full discharge-charge cycle through the dock. Resting voltage after that cycle should sit above 7.5V, and the bar indicator will reflect that correctly.