About this replacement
Pax A910 / A930 — 7.4V Li-Polymer Replacement Battery (JTH-J129)
This is a 7.4V, 850mAh lithium-polymer battery for the Pax A910 and A930 mobile payment terminals. It replaces OEM part JTH-J129 directly. The A910 and A930 are wireless POS devices used in retail and hospitality, and this battery is the same cell format the terminal expects for normal BMS communication.
- A910 and A930 compatibility: Both terminals share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The 7.4V nominal voltage rail matches the charge IC requirements on both models, so one cell works across either unit without modification.
- Bench tested on actual hardware: We ran the JTH-J129 replacement through a full boot sequence, a receipt print cycle, and a wireless transaction on the A910. The BMS accepted the new cell without a handshake error, and the charge IC entered top-off mode correctly after reaching full charge.
- First transaction cycle calibration: After installation, complete one full transaction — boot, process, print receipt, power off — before deploying in a live environment. The A910 maps battery capacity during normal operation and needs at least one complete cycle to report the charge level accurately on screen.
Receipt printer current spike tripping the BMS mid-sale
The thermal printer in the A910 pulls a short, sharp current burst when it fires — higher than the steady draw from the display or wireless radio. On a degraded original battery, the internal resistance rises enough that this spike causes a voltage sag the BMS reads as an overcurrent event, cutting power instantly. A new cell with lower internal resistance absorbs that spike without triggering a cutoff. If the terminal was rebooting specifically at the point of printing, this is the cause — not a firmware fault.
Terminal will not power on after sitting unused for several weeks
Lithium-polymer cells self-discharge slowly during storage. If the A910 sat in a drawer or stockroom long enough, the cell may have dropped below the BMS recovery threshold — typically around 2.5V per cell, or roughly 5.0V across the pack. At that voltage, the BMS locks out power-on as a safety measure and the terminal shows no response to the power button. Connect the original charger and leave it for 30–60 minutes before attempting to power on; if the charge IC detects a recoverable voltage, it will enter trickle mode and bring the cell back up to a safe operating range before allowing a full boot.