Pax S90 Replacement Battery IS497 7.4V 2200mAh

Pax S90 — 7.4V Li-ion Replacement Battery (IS497)

This 7.4V, 2200mAh Li-ion battery replaces the original IS497 cell in the Pax S90 portable payment terminal. It fits the S90 directly and restores full operating capacity for card transaction processing in retail and hospitality environments. Voltage and capacity match OEM spec exactly.

• S90 terminal fit: The S90 uses a 7.4V two-cell Li-ion pack with a BMS handshake that communicates state-of-charge to the terminal's charge IC. This battery carries the same communication protocol, so the terminal reads capacity correctly without throwing a battery fault on the status screen.
• Bench tested on actual hardware: We cycled this battery through full charge and discharge sequences on the S90, running card swipes, receipt prints, and wireless polling simultaneously. The BMS held stable through the combined current draw of the printer motor and the cellular modem without tripping overcurrent protection.
• First deployment tip: After installing this battery, run one complete transaction — tap or swipe through to receipt print — before deploying the terminal on a live till. The S90 maps battery capacity during normal operation and needs at least one full power cycle to display the charge indicator accurately.

Terminal rebooting mid-transaction after battery swap

The S90's receipt printer pulls a short but sharp current spike when the paper feed motor engages. On a freshly installed battery, the BMS hasn't yet profiled the cell and may interpret that spike as an overcurrent event, cutting power momentarily. This causes the terminal to reboot at the exact moment it tries to print — which looks like a software fault but is actually a BMS trip. Run five to ten dummy transactions on the bench before going live so the BMS can establish normal operating thresholds for the printer load.

S90 won't power on after sitting unused in a drawer

Li-ion cells self-discharge at roughly 2–3% per month. If the S90 sat dormant for several months, the cell voltage may have dropped below the BMS recovery threshold — typically around 2.5V per cell, or 5.0V pack total. At that point the BMS locks out discharge to protect the cell, and the terminal shows nothing when you press the power button. Connect the original Pax charger and leave it for at least 60 minutes without pressing any buttons; the charge IC will trickle-charge the pack back above the 6.0V recovery floor before switching to normal charge rate.