Alcatel OT-5047U Replacement Battery TLi021E1 3.7V 1750mAh

Alcatel OT-5047U / U5 HD — 3.7V Li-ion Replacement Battery (TLi021E1)

This is a 3.7V, 1750mAh Li-ion replacement battery for the Alcatel OT-5047U and U5 HD smartphones. It matches OEM part numbers TLi021E1 and CAB2150008C1. Swap it in when the original cell no longer holds charge or the phone shuts down unexpectedly.

• OT-5047U and U5 HD compatibility: Both models run the same 3.7V power rail, use the same connector pinout, and accept the same BMS handshake — one cell covers both variants without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the OT-5047U platform. The BMS accepted the cell without fault codes, and the charge IC stepped through trickle, CC, and CV phases cleanly.
• Fuel gauge recalibration on first use: After installing this cell, disable fast charging and run one complete discharge down to auto-off, then charge uninterrupted to 100%. This gives the fuel gauge IC a clean reference curve for the new cell before high-current charging pushes current into an uncalibrated state.

Sudden shutdown at 20–30% on the OT-5047U after a cell swap

This happens because the fuel gauge IC still holds the discharge curve of the old, degraded cell. When the new cell's actual voltage drops under screen or modem load, the gauge misreads remaining capacity and the phone hits its cutoff threshold early. It is not a fault in the replacement cell — it is a calibration mismatch. Run one full discharge-to-shutdown cycle followed by an uninterrupted charge to 100% to reset the coulomb counter to the new cell's curve.

Phone shows wrong battery percentage after replacement

The OT-5047U's fuel gauge IC stores learned charge data from the previous cell and does not automatically clear it on a swap. The result is percentage jumps, premature low-battery warnings, or a reading that stalls at a fixed number. The fix is a full recalibration cycle: discharge the phone to auto-off under normal use, then charge straight to 100% without interruption. After one cycle, the coulomb counter re-anchors to the new cell's actual capacity and voltage endpoints.