Lenovo A6 Note BL303 Replacement Battery 3.85V 3900mAh

Lenovo A6 Note — 3.85V Li-Polymer Replacement Battery (BL303)

This is a 3900mAh Li-Polymer cell at 3.85V, replacing part number BL303 in the Lenovo A6 Note. It fits models PAGK0027IN, PAGK0027, and L19041. Swap it when the original cell no longer holds a charge through a standard day of calls and screen use.

• A6 Note / PAGK0027 platform fit: These model numbers share the same physical footprint, connector pinout, and BMS handshake protocol. The BL303 part number covers all variants — PAGK0027IN, PAGK0027, and L19041 — because Lenovo used a single battery specification across regional hardware revisions.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the A6 Note platform. The BMS accepted the new cell without fault flags, and the charge IC ramped normally through CC/CV phases with no thermal cutoff events.
• 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 coulomb counter — which otherwise causes erratic percentage readings early on.

Sudden shutdown at 20–30% on the A6 Note after a cell swap

This happens because the fuel gauge IC is still running the old cell's voltage-to-capacity curve. A new Li-Polymer cell holds a different internal resistance profile, so the reported percentage and the actual deliverable voltage diverge under load. When the modem fires a high-current burst — during a call or data transfer — the cell voltage drops below the BMS cutoff threshold even though the gauge still reads 25%. One full discharge-charge cycle without fast charging forces the coulomb counter to reset against the real cell curve and eliminates premature shutdowns.

USB fast charge not engaging on the first cycle after installation

Some A6 Note units fail to negotiate fast charge on the first session with a new BL303 cell. The charge IC performs a handshake with the BMS at the start of each session — a new BMS may not respond within the expected window on cycle one, so the charger falls back to standard 5V input. This is not a fault with the cell or the charger. Complete one full standard-rate charge, then reconnect — the BMS handshake completes correctly on subsequent cycles and fast charge resumes at the expected rate.