Dejavoo Z9 Black Compatible Battery 3.7V 3400mAh Li-ion

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

This 3.7V, 3400mAh Li-ion battery replaces the original cell in the Dejavoo Z9 Black, Z9 v4, and Z8 payment terminals. It restores wireless operation for card transactions when the factory battery no longer holds a usable charge. Capacity data comes from the product specification — 12.58Wh at 3.7V nominal.

• Z9 Black, Z9 v4, and Z8 compatibility: These three terminals share the same battery bay dimensions, connector pinout, and BMS communication protocol. The charge IC in each model negotiates with the same cell parameters, so one replacement covers all three without modification.
• Bench tested on actual hardware: We cycled this cell through repeated charge and full-draw discharge sequences on a Z9 Black unit. The BMS accepted the cell on first boot, voltage held at 3.7V nominal under combined wireless, display, and printer load with no cutoff events triggered.
• First transaction cycle after installation: Complete one full transaction — card tap or swipe through receipt print — before deploying the terminal in a live environment. The Z9 maps battery capacity during normal operation and needs at least one complete power cycle to calibrate the charge indicator correctly.

Payment terminal rebooting mid-transaction after battery swap

The Z9's thermal printer draws a sharp current spike the moment it starts printing a receipt. On a new or recently installed cell, the BMS may read that spike as an overcurrent event and trigger a protective cutoff — which the terminal registers as a sudden power loss and restarts. This is not a faulty battery. The BMS needs one or two transaction cycles to learn the load profile before it stops treating the printer surge as a fault condition. Run two complete transactions — card read through receipt print — and the reboot behaviour typically stops.

Terminal not completing PCI boot sequence on new battery

The Z9 runs a PCI-mandated self-test during every boot that draws a sustained current load before the screen comes on. If the replacement cell hasn't passed its first charge-acceptance handshake with the charge IC, the terminal may stall or restart partway through this sequence. Connect the terminal to its original charger and let it reach a full charge — the battery indicator will move off the flashing icon — before attempting to boot. Once the charge IC has completed one full top-off cycle, the BMS handshake is accepted and the boot sequence completes normally.