Redmi Note 11S BN5D Compatible Battery 3.87V 4900mAh

Redmi Note 11S Series — 3.87V Li-Polymer Replacement Battery (BN5D)

The BN5D is the OEM-matched cell for the Redmi Note 11S and Note 11S 5G (22031116BG). It runs at 3.87V nominal and delivers 4900mAh (18.96Wh). Swap it in when the original cell can no longer hold charge through a full day of use.

• Note 11S and Note 11S 5G compatibility: Both variants share the BN5D connector pinout, cell voltage rail, and BMS handshake protocol. The same physical cell fits either board without modification — the 5G variant uses identical charge IC signalling.
• Bench tested on actual hardware: We cycled this cell through full discharge and charge on Note 11S hardware. The BMS accepted charge handshake correctly, coulomb counter incremented without error flags, and the cell held stable voltage through draw spikes from the modem stack.
• First-cycle fast charge precaution: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate against the new cell's discharge curve before high-current fast charging pushes current into an uncalibrated cell.

Why the Redmi Note 11S reports the wrong battery percentage after a cell swap

The fuel gauge IC on the Note 11S builds its percentage model from the previous cell's discharge curve stored in memory. When a new cell goes in, that stored curve no longer matches the actual cell chemistry. The IC compensates slowly over the first few cycles, which is why percentage readings can appear frozen, jump suddenly, or show 100% while the cell voltage reads lower than expected. One complete uninterrupted discharge down to auto-shutdown, followed by a full charge to 100%, forces the coulomb counter to reset and relearn the new cell's capacity endpoints.

Sudden shutdown at 20–30% on the replacement cell

This happens when the fuel gauge IC still references the old cell's voltage-to-capacity curve, causing it to report 20–30% remaining at a point where the new cell's actual voltage has already dropped below the modem and display's minimum operating threshold. Under combined load — screen on, LTE active, background sync — the cell voltage sags quickly past the BMS cutoff floor. The phone shuts off even though the percentage counter hasn't caught up. Run one full uninterrupted discharge-to-shutdown and charge-to-100% cycle to recalibrate; the premature shutdowns typically stop after the fuel gauge IC has updated its lower voltage endpoint, which sits near 3.4V on this cell under load.