Xiaomi 12 BP46 Replacement Battery 3.89V 4400mAh

Xiaomi 12 Series — 3.89V Li-Polymer Replacement Battery (BP46)

This is a 3.89V, 4400mAh Li-Polymer replacement cell for the Xiaomi 12 smartphone. It fits the Xiaomi 12, 2201123G, 2201123C, and Mi 12S, among other variants in the same hardware family. Swap it in when the original BP46 cell no longer holds enough charge to get through a day of normal use.

• Xiaomi 12 hardware family fit: The 2201123G, 2201123C, and Mi 12S variants share the same battery bay dimensions, connector pinout, and BMS handshake as the base Xiaomi 12. All pull from the same BP46 cell specification, so one replacement covers the full platform range.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on a Xiaomi 12 unit. The BMS accepted the cell without error flags, the charge IC negotiated current correctly, and the fuel gauge IC tracked state-of-charge through the complete cycle without dropping or jumping.
• First-cycle fast charge protocol: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard rate. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before Xiaomi's high-current fast charge protocol pushes peak current into an uncalibrated cell.

Why the Xiaomi 12 reports wrong battery percentage after a BP46 swap

The Xiaomi 12 uses a fuel gauge IC that builds its charge model by tracking coulombs in and out over time. When the original cell ages, the IC adjusts its curve to match a degraded cell. Drop in a fresh BP46 and that old curve no longer maps correctly to the new cell's actual voltage-to-capacity relationship. The result is percentage readings that are off by 10–20% or that jump suddenly. One full discharge-charge cycle at standard rate re-anchors the coulomb counter to the new cell's curve and clears the mismatch.

Sudden shutdown at 20–30% remaining on the replacement cell

This happens when the fuel gauge IC's stored discharge curve predicts remaining capacity that the new cell cannot actually deliver under load. The Snapdragon processor, modem, and display together can pull over 4W during active use, which causes a fast voltage drop in the 3.5–3.6V range on a freshly installed cell with an uncalibrated gauge. The BMS interprets this as an undervoltage event and cuts power to protect the cell. Run the phone down to auto-shutdown from above 80%, then charge to 100% without interruption — after that cycle the gauge reads the new cell's cliff correctly and stops cutting out early.