Lenovo S5 Replacement Battery LB002 3.8V 2800mAh

Lenovo S5 / K520 Series — 3.8V Li-Polymer Replacement Battery (LB002)

This is a 3.8V, 2800mAh Li-Polymer replacement battery for the Lenovo S5 (K520, K520T Pro, PABX0000CN) smartphone. It replaces the original LB002 cell when capacity has degraded past usable thresholds. Dimensions are 85.90 × 62.80 × 3.68mm — verify your existing cell matches before ordering.

• S5 / K520 platform fit: These models share the same battery bay geometry, connector pinout, and BMS handshake protocol. One LB002 cell covers the full K520 lineup without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the S5 platform. The BMS accepted charge from both standard 5V and the device's fast-charge controller. Coulomb counter initialised correctly after one full cycle.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell.

Sudden shutdown at 20–30% on the replacement cell

A new Li-Polymer cell has a steeper voltage drop curve than the worn cell the fuel gauge IC was calibrated against. When the phone pulls high current — active LTE, screen at full brightness, GPS — the cell voltage briefly collapses below the BMS cutoff threshold even though the reported state of charge reads 25%. The phone sees an undervoltage condition and shuts down to protect the cell. One full discharge-to-shutdown followed by a complete charge resets the coulomb counter and aligns the fuel gauge IC to the new cell curve. After that cycle, shutdowns at 20–30% typically stop.

Fast charging not working on the first cycle after replacement

Lenovo's proprietary fast-charge handshake between the charge IC and BMS requires the battery to present within an expected voltage window before high-current delivery is authorised. A new cell shipped in storage state often sits at 3.6–3.7V, which can fall outside the fast-charge entry window on some S5 firmware revisions. Connect the phone to a standard 5V charger and allow it to reach at least 3.85V before reconnecting a fast-charge adapter. The charge IC will then re-negotiate the fast-charge protocol and resume high-current delivery.