Zebra QL420 Replacement Battery AT16293-1 7.4V 3800mAh

Zebra QL420 / QL420+ Series — 7.4V Li-ion Replacement Battery (AT16293-1)

This 7.4V, 3800mAh Li-ion battery replaces part number AT16293-1 in the Zebra QL420, QL420+, and QL420 Plus portable thermal printers. It restores full motor drive voltage to the paper feed and thermal print head. Used across retail, logistics, and healthcare mobile printing deployments.

• QL420 and QL420+ shared platform: Both the QL420 and QL420+ share the same 7.4V battery bay, connector pinout, and BMS handshake protocol — AT16293-1 fits both without modification or adapter.
• Bench tested on actual hardware: We cycled this battery through charge and discharge on a QL420 unit. The BMS negotiated correctly, the thermal head reached operating temperature without voltage sag, and the paper feed motor drew consistent current across multiple print runs.
• First-deploy print sequence: After installing, charge to full and run 5 test label prints before putting the unit into service. The feed motor and thermal head together draw a specific current profile — running that sequence lets the BMS record the correct load signature for the new cell.

Why the QL420 stops printing after sitting in a drawer

Li-ion cells self-discharge at roughly 1–2% per month under no-load storage. After several months, the QL420's BMS may read the pack voltage as below its minimum motor drive threshold — typically around 6.4V — and refuse to power the print head or feed motor. The printer may appear to power on but produce no output. Charge the battery fully before testing; if the pack has dropped into deep-discharge territory, use a charger that includes a recovery or trickle pre-charge mode to bring cell voltage back above 3.0V per cell before standard charging resumes.

Bluetooth drops mid-print job on QL420

The QL420's Bluetooth radio shares the same 7.4V supply rail as the thermal head and feed motor. When the battery is low or a cell is degraded, a sudden current draw from the feed motor causes a momentary voltage sag on that rail. The radio drops its connection to prevent a brownout. This shows up as repeated disconnects when printing multi-label batches, not during idle pairing. Check resting cell voltage — if it reads below 7.0V under no load, the pack no longer holds sufficient charge to handle simultaneous radio and motor current demand.