Lenovo S889T Replacement Battery BL197 3.7V 2050mAh

Lenovo S889T / A800 Series — 3.7V Li-ion Replacement Battery (BL197)

This is a 3.7V, 2050mAh Li-ion replacement battery for the Lenovo S889T, A800, A798T, and S720 smartphones. It carries OEM part number BL197 and fits the original battery bay without modification. Capacity is 2050mAh — matching the factory specification for this handset family.

• S889T / A800 family fit: These models share the same battery bay dimensions, connector pinout, and BL197 BMS handshake across the range. The cell communicates state-of-charge data to the phone's fuel gauge IC over the same three-pin interface, so the OS reads charge status correctly once calibration completes.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the S889T platform. The BMS accepted the charge IC handshake on the first cycle, held voltage above 3.5V through moderate screen-on load, and the cutoff tripped cleanly at the low-voltage threshold without triggering a hard lockout.
• First-cycle fuel gauge reset: On the S889T, disable fast charging for the first complete discharge-charge cycle after fitting this battery. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging pushes load into an uncalibrated coulomb counter — which causes percentage jumping and false full-charge readings on later cycles.

Why the S889T reports wrong battery percentage after a cell swap

The S889T uses a coulomb counter that builds its reference curve against the old cell over hundreds of cycles. When a new cell goes in, the stored curve no longer matches the actual voltage-to-capacity relationship of the fresh Li-ion cell. The phone interpolates percentage from a mismatched table, so it shows 80% when the cell is at 65%, or jumps from 30% to 15% without warning. One full uninterrupted discharge down to auto-shutdown, followed by a full charge to 100%, forces the fuel gauge IC to rewrite its reference map against the new cell.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff failure, not a capacity problem. Under peak modem load or screen brightness, the cell must sustain above roughly 3.4V — if internal resistance is even slightly elevated during the break-in period, voltage sags below the protection threshold and the BMS cuts output before the fuel gauge reaches zero. The phone logs a shutdown at 20–30% because the coulomb counter still shows charge remaining. Let the phone complete two full discharge-charge cycles without heavy background sync or screen-on stress — internal resistance drops as the cell conditions, and the shutdowns stop.