Dejavoo QD2 Replacement Battery 7.4V 2600mAh Li-ion

Dejavoo QD2 / QD4 — 7.4V Li-ion Replacement Battery

This 7.4V, 2600mAh lithium-ion battery replaces the original power cell in the Dejavoo QD2 and QD4 mobile payment terminals. Both terminals share the same battery bay dimensions (66.30 × 40.10 × 20.10mm), connector pinout, and BMS handshake protocol. Swap is straightforward — no tools required.

• QD2 and QD4 compatibility: Both terminals run the same 7.4V power rail, use an identical physical bay, and communicate with the battery over the same BMS data line. One cell covers both models without any hardware modification.
• Bench tested on actual hardware: We cycled this battery through full boot sequences and simulated transaction loads on a QD4 unit. The BMS accepted the handshake cleanly on first power-up and held voltage above the terminal's low-battery cutoff threshold throughout the test load.
• First-deployment cycle on a live terminal: After installing this battery, complete one full transaction cycle before putting the terminal into a high-volume environment. The QD2 and QD4 map cell capacity during normal operation, and the charge indicator on-screen won't read accurately until the terminal completes at least one full power cycle with the new cell seated.

Receipt printer current spike causing mid-transaction BMS trip

The thermal printer in the QD2 and QD4 draws a sharp burst of current the moment it fires — this spike sits on top of the existing wireless radio and display load. On a degraded or deeply discharged replacement cell, that combined draw can breach the BMS overcurrent threshold and cut power instantly. The terminal interprets this as a hard shutdown, not a transaction failure, so the sale may not finalise. Allow the new battery to complete one charge cycle before running it under printer-heavy loads — cell impedance drops after the first full cycle and the BMS is far less likely to trip.

Terminal stuck on boot screen and won't complete PCI startup sequence

The QD2 runs a PCI-compliant boot sequence that includes a battery authentication check early in the startup process. If the BMS handshake isn't resolved within the terminal's timeout window — common when the cell voltage is sitting below 3.5V per cell after storage — the boot sequence stalls and the device holds at the splash screen. Connect the terminal to the original charger and allow it to charge for a minimum of 20 minutes before attempting to power on again. Once the cell climbs above 3.6V per cell, the BMS handshake completes and the boot sequence proceeds normally.