Alcatel OT-991D Replacement Battery TLiB32A 3.7V 1650mAh

Alcatel OT-991D Series — 3.7V Li-ion Replacement Battery (TLiB32A)

This is a 3.7V, 1650mAh Li-ion cell for the Alcatel OT-991D and related OT-991 variants. It replaces OEM part numbers TLiB32A, CAB32A0000C2, BY78, and CAB32A0000C1. The battery fits the OT-991, OT-991 Play, OT-992, and at least 15 additional models sharing the same physical and electrical spec.

• OT-991 platform compatibility: The OT-991, OT-991D, OT-991 Play, and OT-992 all run the same 3.7V battery rail with the same physical footprint (51.67 × 51.00 × 5.34mm) and shared connector pinout. One cell covers the full platform because the BMS handshake requirements are identical across these variants.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on the OT-991 platform. The BMS accepted the cell without error flags, charge termination triggered correctly at 4.2V, and low-voltage cutoff engaged within spec to protect the cell from over-discharge.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging if available and run one complete discharge-to-charge cycle before normal use. The fuel gauge IC on these Alcatel devices calibrates its coulomb counter against the actual discharge curve — skipping this step causes the percentage readout to drift until the IC catches up.

Why the OT-991D reports the wrong battery percentage after a cell swap

The OT-991 platform uses a fuel gauge IC that builds its charge model from accumulated discharge data on the original cell. When a new cell goes in, the IC still references the old cell's learned curve, so the percentage shown is based on incorrect baseline data. The counter drifts until the IC completes a full discharge and recharge cycle against the new cell. Inaccurate readings — such as jumping from 40% to 5% without warning — are the direct result of this mismatch. One full cycle from 100% down to automatic shutoff and back to 100% is enough to resync the counter.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff issue, not a capacity fault. Under high load — modem transmitting, screen at full brightness, or active data sync — the cell voltage can drop sharply below the 3.4V threshold the system uses for emergency shutdown, even while the fuel gauge still shows charge remaining. It happens most often in the first few cycles before the gauge IC has fully mapped the new cell's discharge curve. The fix is to complete two or three full discharge-recharge cycles, which lets the system learn where the real voltage cliff sits on this cell. After calibration, shutoffs at 20–30% should stop.