Dejavoo Z9 Black Replacement Battery 3.7V 2600mAh Li-ion

Dejavoo Z9 Black / Z8 Series — 3.7V Li-ion Replacement Battery

This 3.7V, 2600mAh Li-ion battery replaces the original cell in the Dejavoo Z9 Black, Z9 v4, and Z8 payment terminals. These are mobile POS devices used by merchants to process card transactions wirelessly at the point of sale. The physical dimensions are 67.05 × 21.10 × 18.80mm — confirm your original cell matches before installing.

• Z9 Black, Z9 v4, and Z8 compatibility: These three models share the same battery bay dimensions, 3.7V nominal voltage rail, and connector pinout, which is why they run the same cell. The BMS on each accepts the same charge profile without needing firmware changes.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge passes while monitoring BMS communication with the terminal's charge IC. The protection circuit tripped correctly at both over-voltage and under-voltage thresholds with no anomalies reported.
• First-use calibration on the Z9 Black: After fitting the new battery, complete one full transaction cycle before deploying in a live environment. The terminal maps capacity during normal operation and needs at least one complete power cycle to calibrate the charge indicator accurately.

Receipt printer motor causing BMS overcurrent trip mid-transaction

The Z9's built-in receipt printer draws a sharp current spike the moment the motor engages to advance paper. On a degraded original cell, that spike exceeds the BMS overcurrent threshold and triggers a protective shutoff. A fresh 2600mAh cell handles the spike cleanly because internal resistance is lower and the protection circuit threshold sits well above the printer's draw. If the terminal resets consistently at the moment a receipt prints, the battery is the first thing to replace — not the printer.

Terminal not completing PCI boot sequence after new battery install

The Dejavoo Z9 runs a PCI-mandated security check during every cold boot, and that sequence requires stable voltage above approximately 3.5V throughout. A brand-new cell arriving partially discharged from storage can sit just below that threshold, causing the terminal to stall or loop at the boot screen. Connect the terminal to the charging cradle or USB supply for at least 20 minutes before attempting the first power-on. Once the cell is above 3.6V, the boot sequence completes normally.