Mitac Mio P128 E3MT041202 Replacement Battery 3.7V 1250mAh

Mitac Mio P128 / A200 / A201 Series — 3.7V Li-ion Replacement Battery (E3MT041202)

This 3.7V, 1250mAh Li-ion cell replaces the original battery in the Mitac Mio P128, Mio A200, Mio A201, and Mio 180. It matches the OEM footprint at 53.44 × 37.14 × 7.66mm and uses the same connector pinout as the factory cell. Capacity figure is 4.63Wh as rated in the product data.

• Mio P128 / A200 / A201 / 180 platform fit: These models share a common battery bay geometry, voltage rail, and BMS handshake protocol. A single cell covers the group because the charge IC and connector are identical across the run.
• Bench tested on actual hardware: We cycled this cell through a full charge and discharge sequence on a Mio-series device. The BMS accepted the charge handshake without fault flags and the protection circuit tripped correctly at low-voltage cutoff.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle before normal use. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current cycles begin — otherwise the percentage readout will drift.

Why the Mio P128 reports wrong battery percentage after a cell swap

The Mio P128 uses a fuel gauge IC that stores a learned discharge curve from the previous cell. When you fit a new cell, that stored curve no longer matches the actual voltage-to-capacity relationship of the replacement. The IC keeps referencing the old data, so the percentage shown on screen can read 40% while the actual cell voltage is already near cutoff. One full discharge-then-charge cycle forces the IC to relearn the curve against the new cell. After that single cycle, percentage accuracy stabilises.

Sudden shutdown at 20–30% on the replacement cell

This happens because the display backlight or GSM radio pulls a current spike the fuel gauge IC did not predict, and the cell voltage drops sharply below the BMS cutoff threshold in milliseconds. The phone cuts power before the percentage counter has time to update — so the screen shows 25% right before a hard shutdown. It is not a faulty cell; it is an uncalibrated gauge reading a voltage cliff incorrectly. Run one full discharge cycle to ground and charge back to 100%, and the IC will anchor its low-voltage estimate correctly at the new cell's actual 3.0V floor.