AGPB009-A001 Sony Ericsson Xperia P Replacement Battery 3.7V 1250mAh

Sony Ericsson Xperia P / LT22i — 3.7V Li-ion Replacement Battery (AGPB009-A001)

This is a 3.7V, 1250mAh Li-ion cell built to the AGPB009-A001 specification for the Sony Ericsson Xperia P (LT22, LT22i, Nyphon). It slots into the same battery bay and connects to the same charge IC as the original. Capacity is 1250mAh — identical to factory spec.

• LT22 / LT22i / Nyphon compatibility: All three model variants share the same physical bay dimensions, connector pinout, and BMS handshake voltage. The charge IC on the Xperia P communicates with the cell over the same three-pin interface across every LT22-series board revision, so one cell covers the full lineup.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an LT22i board. The BMS accepted the cell on first connection, charge IC stepped through trickle, CC, and CV phases without fault flags, and the fuel gauge IC registered full capacity at end of charge.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and let the phone complete one full discharge-to-charge cycle without interruption. This gives the fuel gauge IC a clean discharge curve against the new cell before it starts estimating state-of-charge under screen or modem load.

Why the Xperia P reports wrong battery percentage after a cell swap

The Xperia P uses a coulomb-counting fuel gauge IC that builds its state-of-charge model against the discharge curve of the original cell. When a new cell goes in, the stored curve no longer matches the actual cell chemistry and impedance. The gauge reads from its old model and reports percentages that drift from reality — often showing 100% too quickly or dropping sharply under load. One full uninterrupted discharge cycle, from above 95% down to automatic shutdown and back to full charge, resets the learned curve to the new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the fuel gauge IC is still calibrated to a worn cell with higher internal impedance. Under a high-draw event — screen at full brightness, LTE active, GPS on — the new cell's voltage temporarily sags at a lower state-of-charge than the gauge expects, and the protection circuit cuts power before the displayed percentage reaches zero. It is not a faulty cell. Run two full recalibration cycles and the shutdown threshold will track more accurately. If it persists after two cycles, check that the phone's low-battery cutoff voltage is set no higher than 3.4V in the system partition.