Sony Ericsson T600 BSL-14 Replacement Battery 3.7V 650mAh

Sony Ericsson T600 / T66 — 3.7V Li-ion Replacement Battery (BSL-14)

This is a 3.7V, 650mAh Li-ion cell that replaces the original BSL-14 battery in the Sony Ericsson T600 and T66 mobile phones. It fits phones where the original cell has swelled, lost capacity, or simply stopped holding a charge. Capacity figure is 650mAh as listed in the product data.

• T600 and T66 shared platform: Both models draw from the same voltage rail and use the same BSL-14 connector footprint and cell dimensions. A single replacement cell covers both devices without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on a T600 unit. The BMS accepted the charge handshake without error, and the phone held a stable screen-on load without triggering an unexpected cutoff.
• Fuel gauge recalibration on first use: After fitting this cell, run one complete discharge down to automatic shutdown, then charge uninterrupted to 100% before normal use. The T600's fuel gauge IC was calibrated to the original cell curve — this single cycle resets the coulomb counter to the new cell's actual capacity endpoints.

Sudden shutdown at 20–30% on the T600 after a cell swap

The T600 reads remaining charge through a fuel gauge IC that tracks voltage thresholds mapped to the original BSL-14 cell's discharge curve. A new cell has a slightly different voltage-to-capacity curve, so the IC can hit its low-voltage cutoff point while the display still shows 20–30% remaining. This is not a fault in the replacement cell — it is a mismatch between the stored curve and the actual cell. One full discharge-to-shutdown followed by a complete uninterrupted charge corrects this, resetting the gauge to the new cell's real 3.0V floor.

Phone feels warm near the battery during the first few charges

A new Li-ion cell has higher internal impedance than a well-cycled one. The T600's charge IC pushes current at a fixed rate regardless, which generates more heat dissipated across that higher resistance during the first few charge cycles. This is normal and typically resolves after two to three full cycles as the cell's impedance drops. If the phone remains noticeably warm beyond the third full charge, check that the battery contacts are clean and seated flat — a partially lifted cell can concentrate heat at one edge of the contact strip.