Zebra QLN420 Replacement Battery 7.4V 4400mAh

Zebra QLN420 / ZQ630 — 7.4V Li-ion Replacement Battery (P1040687)

This 7.4V 4400mAh Li-ion battery replaces the original power pack in the Zebra QLN420 and ZQ630 mobile printers. Both are compact thermal printers used in retail, healthcare, and logistics for on-the-go receipt and label printing. It also crosses to OEM part numbers P1050667-016 and BTRY-MPP-68MA1-01.

• QLN420 and ZQ630 compatibility: Both models share the same 7.4V battery bay, connector pinout, and BMS handshake protocol — one cell fits both platforms without modification.
• Bench tested on actual hardware: We ran this cell through the QLN420's charge cycle and confirmed BMS communication, thermal cutoff response, and correct charge termination at 8.4V under standard load.
• Motor initialisation after install: After fitting this battery, charge it fully and print five test labels before field deployment. The paper feed motor draws a calibration-level current spike on first use, and the BMS needs those cycles to settle its current profile for the new cell.

Why the QLN420 drops Bluetooth mid-print job

The QLN420's Bluetooth radio and thermal print head share power from the same cell. When battery voltage sags below roughly 6.8V under combined load, the radio doesn't get enough voltage to maintain its transmission window. The printer drops the connection before the print job completes. Keeping the battery above 7.0V resting voltage before a shift eliminates most mid-job disconnects.

Faded or uneven print after a new battery install

Inconsistent print darkness on a new battery usually means the thermal head isn't receiving stable voltage during the heating cycle. This happens when the BMS is still calibrating its discharge curve across the first few cycles. Print density is directly tied to how consistently the head reaches its target temperature — voltage fluctuation during those first prints causes uneven output. Run five to ten full-page prints and the BMS settles; density evens out from there.