Sunmi M2 Payment Terminal Compatible Battery 3.8V 3000mAh

Sunmi M2 / T7820 — 3.8V Li-Polymer Replacement Battery (JKHS)

This is a 3.8V, 3000mAh Li-Polymer battery for the Sunmi M2 and T7820 payment terminals. It replaces OEM part number JKHS and slots directly into the battery bay on both models. Capacity is 3000mAh (11.4Wh), matching the original cell specification.

• M2 and T7820 compatibility: Both terminals share the same battery bay geometry, connector pinout, and BMS handshake protocol — one cell covers both models without modification.
• Bench tested on actual hardware: We cycled this cell through the Sunmi boot sequence and ran multiple transaction loads including receipt printer motor draws. The BMS held voltage within spec and did not trip on printer activation.
• First deployment tip: After fitting the battery, complete one full transaction cycle before going live. The terminal maps battery capacity during normal operation and needs at least one complete power cycle to display an accurate charge indicator.

Terminal rebooting mid-transaction after battery swap

The Sunmi M2 receipt printer draws a short, sharp current spike when it fires. On a new battery that hasn't completed its first charge-discharge cycle, the BMS may read that spike as an overcurrent event and cut output. This is a calibration issue, not a fault with the cell. Run the terminal through two or three complete transaction cycles — print included — and the BMS will normalise its overcurrent threshold. If reboots persist past the third cycle, check that the battery connector is fully seated and reading at least 3.7V at rest.

Sunmi M2 won't power on after sitting unused in storage

Li-Polymer cells self-discharge slowly in storage. If the terminal has sat unused for several weeks or months, the cell voltage may have dropped below the BMS recovery threshold — typically around 2.5V — and the terminal will show no response at all. Connect the charging cable and leave it for 20–30 minutes without pressing the power button. The charge IC needs time to trickle-charge the cell back above the recovery threshold before the BMS will allow a normal boot. Once the screen shows a charging indicator, allow a full charge to 4.2V before powering on.