About this replacement
Motorola Mag One Q5 / Q9 / Q11 / VZ-9 Series — 7.4V Li-ion Replacement Battery (PMNN4423A)
This is a 7.4V, 2600mAh Li-ion battery for the Motorola Mag One Q5, Q9, Q11, and VZ-9 two-way radios, replacing OEM part number PMNN4423A. It fits the compact Mag One body shell and mates with the original charging dock and belt clip. Voltage and cell count match the OEM spec exactly.
- Mag One Q5 / Q9 / Q11 / VZ-9 platform fit: These models share the same 7.4V two-cell Li-ion architecture, connector pinout, and BMS handshake protocol — which is why one pack covers the full range. Swapping between models in this family does not require any firmware or dock adjustment.
- Bench tested on actual hardware: We cycled this pack in a Mag One dock and monitored BMS behaviour through charge acceptance, PTT transmit draw, and termination. The BMS accepted full charge current without tripping and cut off cleanly at the upper voltage threshold.
- First insertion into the Mag One dock: If the dock shows a fault LED on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The Mag One platform requires a clean contact cycle to complete the BMS handshake before charging begins.
Why the Mag One Q5 cuts out mid-transmission on a new PMNN4423A pack
A new Li-ion cell ships at storage voltage — typically 3.6–3.7V per cell, not full charge. When the radio keys up for TX, it pulls a sharp current spike. If the pack has not been charged first, that spike can push the BMS into an overcurrent trip, cutting the transmission instantly. This is not a faulty pack — it is the BMS protecting cells that are below the load threshold. Charge the battery fully in the dock before first use on-radio, and the issue does not recur.
Bar indicator showing one fewer bar than expected after fitting a new PMNN4423A
The Mag One Q-series uses a voltage-threshold bar indicator — it reads resting cell voltage and maps it to bars, with no fuel gauge chip involved. A new pack at storage voltage reads lower than a freshly charged pack, so the indicator correctly shows fewer bars even though the cell is not depleted. Run the pack through one full charge cycle in the dock. After a full charge, the resting voltage should sit above 8.2V and the indicator will reflect that.