Sony Ericsson Xperia SP Replacement Battery 3.7V 2300mAh

Sony Ericsson Xperia SP / M35i Series — 3.7V Li-Polymer Replacement Battery (1266-340.1 / LIS1509ERPC)

This 3.7V, 2300mAh Li-Polymer cell replaces the original battery in the Sony Ericsson Xperia SP, M35i, M35c, and M35h smartphones. It matches the OEM dimensions at 90.07 × 59.50 × 3.50mm and seats flush behind the rear cover without modification. Voltage and capacity match the original spec — no firmware flags or bootloop triggers during our testing.

• Xperia SP / M35 platform fit: The M35i, M35c, and M35h all run the same power rail and share the same connector pinout and BMS handshake protocol as the SP. One cell covers all variants without any wiring or adapter changes.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the Xperia SP. The BMS accepted the handshake, the charge IC reached termination cleanly, and no thermal events occurred during constant-current phase.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate against the new cell's discharge curve before high-current charging pushes current into an uncalibrated state.

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

The Xperia SP uses a coulomb counter in the fuel gauge IC that builds its reference model from historical charge and discharge cycles on the original cell. When a new cell goes in, that reference is stale and no longer matches the new cell's actual voltage-to-capacity curve. The result is percentage readings that jump, stall, or show full charge well before the cell is actually full. One full uninterrupted discharge down to auto-shutdown followed by a complete charge to 100% forces the IC to rebuild its curve against the new cell. After that cycle, percentage accuracy stabilises.

Sudden shutdown at 20–30% on the Xperia SP

This happens when the cell voltage drops sharply under load — typically when the modem transmits or the display runs at full brightness — even though the reported percentage still shows charge remaining. The Xperia SP's power IC cuts the system off the moment cell voltage sags below approximately 3.4V to protect the cell, regardless of what the fuel gauge reports. A degraded original cell hits this voltage cliff early; a fresh replacement cell should hold voltage flat until well below 15%. If shutdown still occurs early after a replacement, run one full recalibration cycle and check that the rear cover is seated without flex pressing on the cell.