Alcatel One Touch POP S3 TLp020A2 Replacement Battery 3.8V 2100mAh

Alcatel One Touch POP S3 / OT-5050 Series — 3.8V Li-ion Replacement Battery (TLp020A2)

This is a 3.8V, 2100mAh Li-ion battery for the Alcatel One Touch POP S3 and OT-5050 series smartphones. It replaces OEM part numbers TLp020A2 and TLi020A1. It fits the OT-5050, OT-5050A, OT-5050Y, and related variants where the original cell has degraded or failed.

• OT-5050 series fit: The OT-5050, OT-5050A, and OT-5050Y share the same battery bay dimensions, connector pinout, and BMS handshake. All run off the same 3.8V nominal rail, so one cell covers the full variant range without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the OT-5050 platform and confirmed the BMS accepted the new cell without fault codes, held charge cutoff at 4.2V, and triggered low-voltage protection at the correct threshold.
• Fuel gauge recalibration on first install: After fitting this battery, run one complete discharge down to auto-shutdown, then charge uninterrupted to 100% before normal use. The phone's fuel gauge IC is calibrated to the old cell's discharge curve — this full cycle resets the coulomb counter against the new cell so percentage readings stay accurate.

Why the OT-5050 reports wrong battery percentage after a cell swap

The OT-5050 uses a fuel gauge IC that tracks charge by counting coulombs against a learned discharge curve from the original cell. When you swap in a new cell, the IC has no reference data for its actual voltage-to-capacity curve. It maps voltage readings against the old curve, so the percentage shown on screen can be several points off — often reading high early in the discharge and then dropping sharply. One full discharge-charge cycle gives the fuel gauge IC enough data to recalibrate. After that cycle, percentage accuracy returns to normal.

Sudden shutdown at 20–30% remaining on the replacement cell

This happens when the fuel gauge IC hasn't completed recalibration and the cell voltage drops below the modem's minimum operating voltage under load — even though the displayed percentage still looks safe. The modem and screen together draw enough current to cause a voltage sag that triggers the protection circuit, cutting power instantly. It's not a faulty cell — it's a calibration gap. Run one full discharge to auto-shutdown, recharge to 100%, and the coulomb counter will reset. After that cycle, the shutdown threshold and displayed percentage will align correctly.