Sunni P2 LITE SE Compatible Battery 3.8V 2900mAh Li-ion

Sunni P2 LITE SE / T6810 Series — 3.8V Li-ion Replacement Battery (TMPA / TMPC)

This 3.8V 2900mAh Li-ion battery fits the Sunni P2 LITE SE, T6810, T6810H, and T6810M payment terminals. These compact card reader devices are used daily in merchant environments for contactless, chip, and magnetic stripe transactions. Voltage and capacity match OEM spec — TMPA and TMPC part numbers both apply across this model range.

• P2 LITE SE and T6810 series compatibility: The P2 LITE SE and T6810 variants share the same battery bay geometry, voltage rail, and BMS handshake protocol. One cell covers the full range without modification.
• Bench tested on actual hardware: We cycled this cell through full charge-discharge sequences on a T6810 unit. The BMS accepted the handshake on the first boot, charge current stepped down correctly at 4.2V, and the protection circuit tripped cleanly at the low-voltage cutoff threshold.
• First transaction cycle after installation: Complete one full transaction — from terminal wake to receipt print — before deploying in a live environment. The terminal maps battery capacity during normal operation and requires at least one complete power cycle to calibrate the charge indicator accurately.

Payment terminal rebooting mid-transaction after battery swap

The T6810's receipt printer motor draws a brief current spike when it fires — this can trip the BMS overcurrent cutoff on a new cell that hasn't completed an initial calibration cycle. The BMS protection threshold is conservative by design and loosens slightly once the cell registers a full charge-discharge pass. If reboots happen consistently at the point of printing, run the terminal through one complete charge cycle first. After that cycle, the BMS threshold aligns correctly with the motor-start surge profile of the printer.

Terminal not powering on after sitting unused in a drawer

Li-ion cells self-discharge at roughly 2–3% per month. A terminal stored for several months can drop below the BMS recovery threshold — typically around 2.5V per cell — at which point the protection circuit blocks output entirely to prevent damage. Plugging the terminal directly into the OEM charger and leaving it for 20–30 minutes allows the charge IC to apply a pre-charge trickle current that brings the cell back above the recovery threshold. Once voltage climbs past approximately 3.0V, the BMS re-enables output and the terminal boots normally.