About this replacement
Square S6 / S8 — 3.7V Li-Polymer Replacement Battery (PR-244147A)
This is a 3.7V 520mAh lithium-polymer battery built to OEM part number PR-244147A. It fits the Square S6 and S8 portable payment terminals. When the original cell degrades after repeated charge cycles, this replacement restores wireless transaction capability without a constant power connection.
- S6 and S8 compatibility: Both terminals run the same 3.7V power rail and share the same connector footprint and BMS handshake protocol — one battery cell covers both models without any modification.
- Bench tested on actual hardware: We cycled this cell through the S6 boot sequence and card-read workflow. The BMS accepted the cell without fault flags, and the charge IC entered normal CC/CV charging without triggering a protection cutoff.
- First deployment tip: After fitting this battery, complete one full transaction cycle before deploying the terminal in a live environment. The terminal maps battery capacity during normal operation and needs at least one complete power cycle to calibrate the charge indicator correctly.
Why the S6 reboots mid-transaction after a battery swap
The S6 pulls a combined current spike during card read plus wireless transmission. On a new cell that hasn't completed its first charge cycle, internal resistance is slightly elevated — enough for the BMS to see a momentary undervoltage event and trigger a protective reset. This isn't a faulty battery. Run the terminal through one complete charge and transaction cycle and the BMS recalibrates its trip threshold against the actual cell characteristics. Reboots during normal use stop after that initial cycle.
Terminal won't power on after sitting unused in a drawer
Lithium-polymer cells self-discharge at roughly 2–3% per month. A terminal stored for six months or more can drop below the BMS recovery threshold — typically around 2.5V — and the protection circuit locks the output entirely. Connect the terminal to its original charger and leave it for 20–30 minutes without pressing the power button. Most charge ICs include a trickle-charge stage that slowly brings the cell back above the 2.8V re-initialisation threshold before switching to normal charging. If the charging indicator doesn't appear within 45 minutes, check that the supply voltage reaching the terminal is within the 5V ±5% spec.