Vivo iQOO 5 5G B-N9 Replacement Battery 3.87V 4200mAh

Vivo iQOO 5 5G — 3.87V Li-Polymer Replacement Battery (B-N9)

This is a 3.87V, 4200mAh (16.25Wh) Li-Polymer replacement battery for the Vivo iQOO 5 5G, V2024A, and V2024. It replaces OEM part number B-N9 directly. Swap it when the original cell has degraded, lost capacity, or failed outright.

• iQOO 5 5G, V2024A, V2024 fit: All three models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The B-N9 cell measures 81.20 × 64.30 × 5.46mm — any deviation would prevent the rear cover from seating or cause connector misalignment.
• Bench tested on actual hardware: We cycled this cell through a full charge and discharge on a V2024 unit. The BMS accepted the cell, reported state-of-charge correctly after calibration, and did not trigger protection cutoff under sustained 5G modem and display load.
• Fuel gauge recalibration after install: 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 pushes current into an uncalibrated cell. Skip this step and percentage readings will drift.

Sudden shutdown at 20–30% on the iQOO 5 5G

This is a voltage cliff issue, not a capacity failure. When the 5G modem and AMOLED display pull current simultaneously, a degraded or uncalibrated cell drops below the BMS cutoff voltage before the percentage gauge reaches zero. The phone shuts down because the cell cannot sustain voltage under that combined load — even though the fuel gauge still shows charge remaining. One full discharge-charge cycle with fast charging off recalibrates the coulomb counter and shifts the reported percentage to match actual cell voltage.

USB-PD fast charge not accepted on the first cycle after replacement

After a cell swap, the charge IC on the iQOO 5 5G may fall back to standard 5W charging on the first cycle. The BMS on a new cell starts with default impedance values, and the phone's charge negotiation reads those values as outside the expected fast-charge window. This is not a fault — it clears after the first full cycle. Complete one standard charge to 100%, allow the phone to cool, then reconnect your fast charger. The phone should resume full fast-charge negotiation from the second cycle onward.