Мегафон T261L Replacement Battery 3.7V 1100mAh Li-ion

Мегафон T261L — 3.7V Li-ion Replacement Battery

This 3.7V, 1100mAh Li-ion cell replaces the original battery in the Мегафон T261L smartphone. It fits directly into the T261L battery bay and connects via the standard three-contact terminal. Capacity is 4.07Wh — matched to the original specification.

• T261L battery bay fit: The cell measures 54.05 × 34.10 × 5.40mm. That matches the T261L's housing recess. The three-contact terminal aligns with the phone's charge management IC and thermistor line, so the board reads cell temperature correctly during charge.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on a T261L-class board. The BMS accepted the cell without fault flags on the first connection. Charge termination triggered correctly at 4.2V and the protection circuit tripped at the expected low-voltage cutoff.
• Fuel gauge recalibration on first use: On first installation, run one complete discharge to shutdown and then charge uninterrupted to 100% before using the phone normally. The T261L's fuel gauge IC calibrates its coulomb counter against that first full cycle — skipping it causes percentage jumps for the first several days of use.

Why the T261L reports wrong battery percentage after a cell swap

The T261L uses a fuel gauge IC that builds its state-of-charge model from learned discharge curves over several cycles. When a new cell goes in, the IC is still referencing the curve of the old, degraded cell. The mismatch causes the percentage reading to lag or jump — particularly between 40% and 20%, where a fresh cell has more capacity than the old curve predicts. One full discharge-to-shutdown followed by an uninterrupted charge corrects the baseline. After two to three cycles the gauge settles to within a few percent of actual remaining capacity.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem radio or screen draws a short burst of current and the cell voltage drops below the BMS protection threshold — even though the gauge still shows charge remaining. On an uncalibrated fuel gauge, the percentage displayed does not reflect real cell voltage under load. The BMS sees the voltage cliff and cuts output to protect the cell. The fix is the same calibration cycle: full discharge to automatic shutdown, then a full charge to 100% without interruption. After that cycle the gauge tracks actual voltage under load more accurately and the premature shutdowns stop.