Pax Q80 Compatible Battery 7.4V 650mAh IS690

Pax Q80 — 7.4V Li-Polymer Replacement Battery (IS690)

This 7.4V, 650mAh lithium-polymer battery replaces the IS690 cell in the Pax Q80 portable payment terminal. The Q80 is a compact wireless POS device used for card and mobile payment processing in retail and hospitality environments. Swap this in when the original cell no longer holds enough charge to complete transactions away from a power source.

• Pax Q80 fit: The Q80 uses a dedicated battery bay with a fixed connector orientation and a BMS handshake tied to the terminal's firmware. This cell matches the physical footprint (53.30 × 34.10 × 8.00mm), connector pinout, and voltage rails the Q80 expects at boot.
• Bench tested on actual hardware: We cycled this cell through the Q80's boot sequence and ran it through card-read and receipt-print loads. The BMS accepted the handshake on first power-up, and charge reporting initialised normally within one full charge cycle.
• First transaction cycle: After installation, complete one full transaction — including a receipt print — before deploying in a live environment. The Q80 maps battery capacity during normal operation and needs at least one complete power cycle to calibrate the charge indicator correctly.

Terminal rebooting mid-transaction after a battery swap

The Q80's receipt printer draws a sharp current spike the moment it fires. On a new cell that hasn't completed a calibration cycle, the BMS can read that spike as an overcurrent event and trip the protection circuit — cutting power mid-sale. This isn't a faulty battery. The BMS needs to record one full operating cycle before it correctly distinguishes normal printer current from a fault condition. Run the terminal through a complete boot, a test transaction, and a printed receipt before putting it on the counter.

Q80 not powering on after sitting unused in storage

Lithium-polymer cells self-discharge over time. If a Q80 sits unused for several months, the cell voltage can drop below the BMS recovery threshold — typically around 2.5V per cell — and the terminal will show no response when the power button is pressed. Connect the terminal to its original charger and leave it for at least 30 minutes without pressing any buttons. Most BMS circuits include a trickle-charge recovery mode that kicks in below 3.0V and slowly brings the cell back into normal operating range before allowing a full charge.