About this replacement
Sony Ericsson Xperia X10 / X10a — 3.7V Li-ion Replacement Battery (BST-41)
This is a 3.7V 2600mAh Li-ion cell replacing the OEM BST-41 battery in the Sony Ericsson Xperia X10 and X10a smartphones. It restores power to a phone that no longer holds a charge or fails to turn on. Voltage and capacity match the original cell specifications from the product data.
- X10 and X10a compatibility: Both handsets share the same BST-41 footprint, voltage rail, and connector pinout. The BMS handshake between the charge IC and this cell is consistent across both model variants, so no hardware modification is needed.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge on the X10 platform. The BMS responded correctly at both the low-voltage cutoff and top-of-charge limits, with no unexpected protection trips during load simulation.
- Fuel gauge recalibration on first install: After fitting this cell, disable fast charging and run one full discharge-to-charge cycle before normal use. This lets the Xperia X10's fuel gauge IC map the new cell's discharge curve before high-current charging begins on an uncalibrated register.
Why the Xperia X10 reports wrong battery percentage after a cell swap
The X10 uses a fuel gauge IC that tracks charge state against a stored discharge curve from the previous cell. When you install a new cell, that stored curve no longer matches the actual chemistry of the replacement. The IC continues reading from its old calibration, so displayed percentages drift from real charge state. One complete discharge-charge cycle overwrites the calibration register and brings percentage reporting back into alignment.
Sudden shutdown at 20–30% on the replacement cell
This happens when the modem radio or display triggers a high-current draw spike and the cell voltage collapses faster than the fuel gauge expects. The BMS reads the voltage drop as a hard cutoff threshold and shuts the phone down even though the displayed percentage looks safe. It is a calibration gap, not a faulty cell. Run two full discharge cycles and check that the resting cell voltage reads at or above 3.6V before each startup.