About this replacement
Motorola XPR3300 / XPR3550 Series — 7.4V Li-ion Replacement Battery (PMNN4490)
This 7.4V 3400mAh Li-ion battery replaces the PMNN4490 pack in Motorola's XPR3300, XPR3300e, XPR3550, and XPR3550e digital two-way radios. It uses the same cell configuration and BMS handshake profile as the factory pack. Swap it in when the original no longer holds a charge across a full shift.
- XPR3300 / XPR3550 platform fit: Both the standard and 'e' variants share the same 7.4V battery rail, connector pinout, and BMS communication protocol — that's why a single pack covers all four models. The 'e' suffix indicates enhanced display, not a different battery compartment.
- Bench tested on actual hardware: We ran this pack on an XPR3300e dock and monitored BMS handshake, charge acceptance, and PTT transmit current draw. The protection circuit held stable across repeated high-current transmit bursts without tripping into cutoff.
- First insertion on a Motorola 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 XPR platform requires a clean contact cycle to complete the BMS handshake before charging begins.
Why the XPR3300 cuts out mid-transmission on a new battery
The XPR3300's BMS has an overcurrent threshold that trips when the PTT transmit spike exceeds what the pack expects at its current state of charge. A new cell shipped at storage voltage — typically around 3.7–3.8V per cell — has higher internal impedance than a fully charged cell. That impedance causes a sharper voltage sag under transmit load, which the BMS reads as a fault and cuts the output. Charge the pack fully to 8.4V before the first use and the transmit spike will stay within the BMS window.
Bar indicator showing one fewer bar than expected on a new PMNN4490
The XPR series uses voltage-threshold bar indicators, not a fuel gauge chip — so the display reflects real-time terminal voltage only. A new pack at storage voltage reads lower than a freshly charged pack, and the radio correctly shows one or two bars rather than full. This is not a fault with the cell. Run a full charge cycle until the dock LED goes solid green, then reinsert the pack — the bar display will update immediately to reflect the higher resting voltage above 8.0V.