Redmi A2 Replacement Battery BN5F 3.82V 5000mAh

Redmi A2 — 3.82V Li-Polymer Replacement Battery (BN5F)

This is a 3.82V, 5000mAh Li-Polymer replacement battery for the Redmi A2 smartphone (models 23026RN54G and 23028RN4DG). It replaces OEM part BN5F using the same cell dimensions — 94.00 × 64.30 × 4.80mm — and matches the original connector and flex cable routing. Capacity is rated at 19.1Wh.

• A2 variant fit — 23026RN54G and 23028RN4DG: Both regional variants of the Redmi A2 use the same BN5F cell format, voltage rail, and BMS connector. The physical dimensions and tab placement are identical across both model numbers, so one cell covers both.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a Redmi A2 unit. The BMS accepted charge current without fault codes, and cell voltage held steady under screen-on and modem load without triggering low-voltage cutoff prematurely.
• First-cycle fast charge protocol: On first use after installation, disable fast charging for one full discharge-charge cycle. This lets the fuel gauge IC recalibrate against the new cell's discharge curve before the charge IC pushes high current into an uncalibrated cell.

Why the Redmi A2 reports wrong battery percentage after a BN5F swap

The Redmi A2 uses a coulomb counter in the fuel gauge IC that tracks charge state against the original cell's discharge curve. When a new cell goes in, the IC still references the old curve — so the percentage displayed can be off by 10–20% in either direction. This is not a fault in the replacement cell. One complete discharge to shutdown followed by a full uninterrupted charge resets the coulomb counter and aligns it to the new cell's actual curve. After that cycle, percentage accuracy stabilises.

Sudden shutdown at 20–30% on the new cell

This happens when the cell voltage drops below the BMS cutoff threshold under high-draw load — typically when the modem fires or the screen is at full brightness — even though the UI shows charge remaining. The fuel gauge is still running on an uncalibrated curve, so it overestimates remaining capacity. The BMS cuts power when cell voltage hits approximately 3.4V under load, regardless of what the OS reports. Run one full discharge-to-shutdown cycle and recharge to 100% to let the fuel gauge IC recalibrate to the new cell.