Redmi 9A Compatible Battery BN56 3.85V 4900mAh Li-Polymer

Redmi 9A / 9C Series — 3.85V Li-Polymer Replacement Battery (BN56)

This is a 3.85V, 4900mAh Li-Polymer cell built to replace the BN56 battery in the Redmi 9A and 9C smartphones. It fits models M2006C3LVG and M2006C3LI, among others in the same hardware family. Swap it when the original cell no longer holds a charge or the phone shuts down unexpectedly before reaching 0%.

• 9A and 9C platform fit: Both the 9A and 9C share the same physical cell envelope, connector pinout, and BMS handshake protocol — that is why a single BN56 cell covers the full range. The fuel gauge IC on each model reads the same charge curve.
• Bench tested on actual hardware: We cycled this cell on a 9A unit and confirmed the BMS accepted the charge handshake without fault codes. Capacity read-back settled to within 2% of the rated 4900mAh after the second full cycle.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging begins — skipping this step is the main reason percentage readings jump around after a swap.

Why the Redmi 9A reports wrong battery percentage after a cell swap

The Redmi 9A uses a coulomb counter tied to a fuel gauge IC that was calibrated against the original cell's discharge curve. When a new cell goes in, that learned curve no longer matches the actual voltage-to-capacity relationship of the replacement. The IC keeps using stale data, so it shows 40% when the real remaining capacity is closer to 15%. One full discharge down to automatic shutdown, followed by a full uninterrupted charge to 100%, forces the IC to rewrite its internal table against the new cell.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff problem, not a capacity problem. Under high load — active mobile data, screen at full brightness, or a background sync burst — the cell voltage drops sharply below the BMS cutoff threshold even though the fuel gauge still shows charge remaining. The gauge reads stored capacity; the BMS reacts to live voltage. If the fuel gauge IC has not yet completed its first recalibration cycle, it underestimates how close the cell is to the cutoff point. Run one full discharge-charge cycle and confirm resting voltage reads at least 3.85V at 100% before assuming the cell is faulty.