C11P1321 Asus PadFone E Compatible Battery 3.8V 1850mAh

Asus PadFone E / A68M — 3.8V Li-Polymer Replacement Battery (C11P1321)

This is a 3.8V, 1850mAh Li-Polymer replacement battery for the Asus PadFone E and A68M smartphones. It carries OEM part number C11P1321 and fits the original battery slot without modification. Capacity is rated at 7.03Wh, matching the factory specification for this device.

• PadFone E and A68M compatibility: Both models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — 57.14 x 55.70 x 4.29 mm cell with a matched communication line for the fuel gauge IC. One part number covers both.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the PadFone E platform. The BMS accepted the charge handshake on first connection, hit 4.35V at full charge, and the protection circuit tripped cleanly at the low-voltage cutoff without latching.
• Fuel gauge recalibration on first cycle: After fitting this cell, disable fast charging and run one complete discharge down to auto-shutdown, then charge fully to 100%. The fuel gauge IC on the PadFone E calibrates its coulomb counter against the cell's actual discharge curve on that first cycle — skipping it leaves the percentage readout inaccurate until it completes naturally.

Sudden shutdown at 20–30% on the PadFone E after a cell swap

The PadFone E's modem and display draw a combined surge current that a freshly installed, uncalibrated cell can fail to sustain at lower state-of-charge. The cell voltage dips below the BMS cutoff threshold under that load — even though the fuel gauge still reads 20–30% — and the phone shuts down. This is a calibration gap, not a faulty battery. Run one full discharge-to-shutdown cycle without fast charging, then charge uninterrupted to 100%. After that cycle the coulomb counter maps correctly to the new cell and the shutdowns stop.

Phone warm near the battery compartment during the first charge

A new Li-Polymer cell has higher internal impedance than a cycled one, and the charge IC compensates by pushing more voltage to maintain current — that conversion loss shows up as heat near the battery bay. It is most noticeable in the first two to three charge cycles and drops off as the cell's impedance normalises. If the phone becomes hot enough to trigger the thermal warning, remove it from the charger, let it cool to room temperature, then resume charging. By the third full cycle the warmth during charge should be no different from the original battery.