Lenovo A8 Replacement Battery BL229 3.7V 2100mAh

Lenovo A8 / A806 / A808T — 3.7V Li-ion Replacement Battery (BL229)

This is a 3.7V, 2100mAh Li-ion replacement battery for the Lenovo A8, A806, and A808T smartphones. It replaces OEM part BL229 and fits the original battery bay without modification. Install it when the original cell no longer holds a full charge or the phone shuts down unexpectedly.

• A8 / A806 / A808T platform fit: All three models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — that is why one BL229 cell covers the entire A8 line. Swapping between these variants does not require any adapter or firmware change.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the A808T. The BMS accepted the charge handshake on the first connection, held voltage within spec across the full discharge curve, and tripped the protection circuit cleanly at the low-voltage cutoff threshold.
• Fuel gauge recalibration on first use: After fitting a new BL229 cell, disable fast charging and run one full discharge-to-charge cycle. The Lenovo A8's fuel gauge IC is calibrated to the old cell's discharge curve — this single cycle lets it remap against the new cell before any high-current charging session pushes current into an uncalibrated state.

Sudden shutdown at 20–30% on a new BL229 cell

This is a voltage cliff, not a faulty battery. Under peak load — modem activity, screen at full brightness, or GPS — the new cell briefly drops below the voltage floor the A8's power management IC uses as its cutoff signal. The phone interprets that voltage dip as a dead cell and shuts down, even though the fuel gauge still shows charge remaining. One full discharge-charge cycle tightens the coulomb counter's mapping and moves the apparent cutoff point down to where it belongs. If shutdowns persist after two full cycles, confirm the cell voltage at shutdown sits above 3.4V — anything lower points to a high-impedance cell rather than a calibration issue.

Battery percentage jumping erratically after cell replacement

The Lenovo A8 stores its fuel gauge calibration data against the original cell's specific discharge curve. When you fit a new BL229, that stored data no longer matches the cell it is measuring, so the reported percentage jumps — sometimes 10–15 points in seconds. This is the coulomb counter losing confidence in its own estimate, not a hardware fault. Charge the phone to 100%, let it drain fully until it powers off on its own, then charge back to 100% without interruption. After that single cycle the fuel gauge IC resets its reference points and percentage reporting stabilises.