About this replacement
Zebra IMZ320 / MZ320 Series — 7.4V Li-ion Replacement Battery (BT17790-1)
This 7.4V, 1500mAh lithium-ion battery replaces the original pack in Zebra's IMZ320, MZ220, MZ320, and MZ420L mobile printers. These are compact receipt and label printers used in retail checkouts, warehouse scanning, and field service runs. Swap the old pack, seat the connector, and the printer powers on without any configuration step.
- IMZ320 / MZ220 / MZ320 / MZ420L compatibility: All four models share the same 7.4V battery bay, connector pinout, and BMS handshake protocol — one pack covers the full line. The BMS communicates state-of-charge to the printer's firmware so charge indicators read correctly on the host app.
- Bench tested on actual hardware: We ran this pack on an MZ320 unit and confirmed the BMS initialised cleanly, the charge LED cycled through its normal sequence, and the thermal print head received stable voltage across the full discharge curve without undervoltage dropouts.
- First-deployment print sequence: After fitting a new pack, charge it fully, then run five test label prints before putting the unit into a shift. The paper feed motor draws a short high-current pulse on each cycle — this sequence confirms the BMS current profile has settled correctly for the new cells and prevents nuisance low-battery alerts mid-job.
Why the MZ320 won't print after sitting unused for several weeks
Mobile printers left on a shelf with a partially depleted battery will self-discharge past the BMS protection threshold — typically around 2.5V per cell. When voltage drops that low, the BMS locks the output rail to prevent cell damage. The printer powers on but sends no current to the motor or thermal head, so it appears dead or throws a battery fault code. Connect the pack to the OEM charger and leave it for at least 30 minutes before attempting to print — most BMS circuits require a trickle-charge recovery phase before they re-enable the output. If the pack does not recover past 6.8V within an hour on charge, the cells have been over-discharged beyond recovery and the pack needs replacement.
Print coming out faded or striped with a battery that shows partial charge
Faded or inconsistently dark prints are almost always a thermal head voltage problem, not a paper or settings issue. The IMZ320's thermal head needs a stable supply to reach correct operating temperature — if the battery's internal resistance has risen due to cell aging, voltage sags under the head's heating load and temperature drops mid-print. The result is uneven darkness, light stripes, or entire lines that fail to transfer. Check the battery's resting voltage first: a healthy 7.4V Li-ion pack should read 7.9–8.3V fully charged. Anything below 7.4V at rest means the cells are worn and the pack should be replaced to restore consistent print density.