Dejavoo M8 POS Terminal Compatible Battery 3.6V 700mAh

Dejavoo M8 / M5 — 3.6V Ni-MH Replacement Battery (A0285A)

This is a 3.6V, 700mAh Ni-MH rechargeable battery for the Dejavoo M8 and M5 portable payment terminals. It replaces OEM part numbers A0285A, U0156783, and A0170A. If your terminal is dying mid-shift or no longer holding a charge through a full day of transactions, this is the correct replacement cell.

• M8 and M5 compatibility: Both terminals share the same battery bay dimensions, voltage rail, and connector pinout. The BMS handshake protocol is identical across both models, so one cell covers either unit without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on an M8 unit. The BMS accepted the cell on first boot, charge IC entered top-off mode correctly, and the terminal completed its PCI boot sequence without fault codes.
• First transaction calibration: After installing this battery, run one complete transaction cycle — including receipt print — before deploying the terminal in a live environment. The M8 maps battery capacity during normal operation and needs at least one full power cycle to calibrate the charge indicator accurately.

Terminal not completing PCI boot sequence after battery swap

The M8 runs a PCI compliance check at every cold boot, and this sequence draws a short current spike as it initialises the secure processor and wireless module simultaneously. A new cell that hasn't completed a full charge cycle may dip below the BMS low-voltage threshold during this spike, causing the boot to stall or loop. The fix is straightforward: charge the terminal fully before the first boot rather than powering it on straight out of the packaging. Once the cell reaches full charge and the BMS registers the healthy voltage, the PCI sequence completes normally.

Terminal won't power on after sitting unused in a drawer

Ni-MH cells self-discharge at roughly 1–3% per day at room temperature. A terminal left unused for several weeks can drop its cell below 2.8V — the point where the BMS locks out discharge to prevent cell damage. The unit will appear completely dead and won't respond to the power button. Connect the terminal to its charger and leave it for at least 60 minutes before attempting to power on; most BMS circuits require the cell to recover to approximately 3.2V before they release the discharge lockout.