Sony Ericsson BA950 Xperia A Replacement Battery 3.7V 2050mAh

Sony Ericsson Xperia A / ZR — 3.7V Li-ion Replacement Battery (BA950)

The BA950 is a 3.7V, 2050mAh (7.59Wh) Li-ion cell that fits the Sony Ericsson Xperia A (SO-04E), Xperia ZR, C550X, and several additional variants. It replaces the original factory cell when the existing battery swells, loses hold capacity, or triggers unexpected shutdowns. Voltage and connector spec match the OEM unit exactly.

• Xperia A / ZR platform compatibility: These models share the same 3.7V power rail, BA950 connector footprint, and BMS handshake protocol — which is why one cell covers the full model range without modification or adapter.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on Xperia ZR hardware. The BMS accepted the cell without fault codes, and the charge IC moved through trickle, constant-current, and constant-voltage phases cleanly.
• Fuel gauge recalibration on first use: On first use after installation, run one full discharge down to auto-shutdown, then charge uninterrupted to 100%. This gives the fuel gauge IC a complete reference cycle against the new cell's discharge curve before the OS starts reporting percentages.

Sudden shutdown at 20–30% on the BA950 replacement cell

This is a voltage cliff issue, not a capacity defect. Under modem transmission load or screen-on bursts, the new cell's terminal voltage drops faster than the fuel gauge IC expects — because the IC is still running the discharge curve from the old, degraded cell. The phone's protection circuit reads the voltage drop as a critical low and shuts down before the percentage counter reaches zero. One full discharge-charge cycle recalibrates the coulomb counter and eliminates the premature cutoff in most cases.

Phone warm near the battery compartment during the first charge

A new high-impedance cell generates more heat than a broken-in one during the constant-current phase of charging. The charge IC pushes current into higher internal resistance, and that energy dissipates as heat around the battery compartment. This is normal for the first two to three cycles and reduces as internal resistance drops with use. If the phone stays warm past the third full charge, check that the charger output does not exceed 5V/1A — higher voltages force the charge IC harder on an uncalibrated cell.