Xiaomi 14 CIVI Compatible Battery BN4F 3.91V 4600mAh

Xiaomi 14 CIVI / Civi 4 Pro 5G — 3.91V Li-Polymer Replacement Battery (BN4F)

This is a 3.91V, 4600mAh (17.99Wh) Li-Polymer replacement battery carrying OEM part number BN4F. It fits the Xiaomi 14 CIVI (24053PY09C, 24053PY09I) and the Civi 4 Pro 5G. It replaces the original cell when the phone can no longer hold charge or shuts down unexpectedly under load.

• 14 CIVI and Civi 4 Pro 5G compatibility: Both devices share the BN4F cell format, connector pinout, and BMS handshake protocol — the same fuel gauge IC and charge controller are used across the 24053PY09C and 24053PY09I board revisions, so one cell covers both variants.
• Bench tested on actual hardware: We ran the BN4F cell through a full charge-discharge cycle on a Xiaomi 14 CIVI unit. The BMS accepted charge without fault codes, and the fuel gauge IC registered the cell correctly after one complete calibration cycle.
• First-cycle fast charge protocol: On first use after installation, disable Xiaomi HyperCharge for one full discharge-to-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current fast charging pushes significant current into an uncalibrated coulomb counter.

Why the Xiaomi 14 CIVI reports wrong battery percentage after a cell swap

The fuel gauge IC stores a learned discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches the actual cell chemistry, so the percentage readout drifts — often reading high early, then dropping fast near the bottom. The fix is one full uninterrupted discharge down to auto-shutdown, followed by a full charge to 100% with fast charging off. After that cycle, the coulomb counter resets its reference points against the new cell and percentage reporting stabilises.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or display pulls a current spike that drops the cell voltage below the BMS cutoff threshold — even though the gauge still shows charge remaining. A fresh cell with an uncalibrated fuel gauge IC is especially prone to this in the first few cycles. Run one full calibration cycle first, then check whether the shutdowns persist. If they continue past three full cycles, measure resting cell voltage directly — it should sit above 3.7V at 20% reported charge.