Lenovo K5 Replacement Battery LB003 3.85V 2900mAh

Lenovo K5 Series — 3.85V Li-Polymer Replacement Battery (LB003)

This is a 3.85V, 2900mAh Li-Polymer cell replacing part number LB003. It fits the Lenovo K5, K5 Dual SIM, and K350t smartphones. Capacity figures come from the product data — 11.17Wh total stored energy at rated voltage.

• K5, K5 Dual SIM, and K350t compatibility: All three models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The K350t is a regional variant of the K5 platform — same 3.85V rail, same fuel gauge IC communication lines, same physical footprint at 77.80 × 63.14 × 3.80mm.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a K5 unit. The BMS accepted the cell without a fault code on first power-up. Charge termination triggered correctly at full capacity and the protection circuit tripped as expected on a simulated short.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-charge cycle. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging begins on an uncalibrated cell.

Why the K5 reports wrong battery percentage after a cell swap

The K5 uses a fuel gauge IC that builds its charge model from the previous cell's discharge history. When you swap to a new cell, the IC still references the old curve. This causes the percentage readout to lag or jump — sometimes showing 100% when the cell isn't full, or dropping fast through the mid-range. One full discharge down to auto-shutdown followed by an uninterrupted charge to 100% forces the IC to recalibrate against the new cell. After that cycle, percentage reporting stabilises.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem fires a high-current burst — during a call, data sync, or GPS fix — and the cell voltage dips below the BMS protection threshold under that load spike. A partially calibrated fuel gauge makes this worse because the displayed percentage doesn't reflect actual remaining capacity. The fix is the same recalibration cycle: one full discharge and charge with fast charging off. If shutdowns continue past two full cycles, check that the battery connector is fully seated — a half-latched connector raises contact resistance and amplifies voltage sag under load.