Lenovo PB2-690N Tab M10 Replacement Battery 3.85V 4000mAh

Lenovo Phab 2 / PB2-690N — 3.85V Li-Polymer Replacement Battery (L16D1P32)

This is a 3.85V, 4000mAh Li-Polymer replacement battery for the Lenovo Phab 2 and Phab 2 Pro tablets. It fits the PB2-690N and PB2-670N chassis and uses Lenovo OEM part number L16D1P32. Voltage and connector match the original cell exactly.

• PB2-690N / PB2-670N / Phab 2 Pro compatibility: These models share the same battery bay dimensions, 3.85V supply rail, and L16D1P32 connector pinout. The BMS handshake protocol is identical across the Phab 2 lineup, so one cell covers all four fit models listed above.
• Bench tested on actual hardware: We ran this cell on a PB2-690N unit and monitored BMS charge acceptance across a full cycle. The protection circuit engaged correctly at the 4.35V charge ceiling and cut off cleanly at the low-voltage floor — no erratic reporting during discharge.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and complete one full discharge-charge cycle at standard current. The Phab 2's fuel gauge IC was calibrated against the original cell's discharge curve — one slow cycle lets it map the new cell before resuming high-current charging.

Why the Phab 2 reports wrong battery percentage after a cell swap

The Phab 2 uses a coulomb-counter-based fuel gauge IC that builds its state-of-charge model from the original cell's charge and discharge history. When a new cell goes in, that learned curve no longer matches the actual cell chemistry in the bay. The IC reports whatever percentage it calculated against the old curve, which is why you see jumpy or offset readings immediately after installation. One complete discharge to automatic shutdown followed by a full charge at standard current forces the IC to reset its reference points against the new cell.

Sudden shutdown at 20–25% remaining on the replacement cell

This happens when the fuel gauge IC has not yet recalibrated and the cell voltage drops below the system's minimum load threshold before the reported percentage reaches zero. Under display or processor load, the Phab 2's PMIC pulls current the under-calibrated cell cannot sustain, and the BMS trips a hard cutoff to protect the cell. The OS sees this as an unexpected power loss — not a graceful shutdown. Run one full slow cycle as described above; if cutoffs persist after two cycles, confirm the resting open-circuit voltage sits between 3.85V and 4.35V after a full charge.