About this replacement
Vivo Nex 3 Series — 3.85V Li-Polymer Replacement Battery (B-G9)
This is a 3.85V, 4400mAh lithium-polymer cell built to fit the Vivo Nex 3, Nex 3S 5G, Nex 3 5G, and V1950A. It replaces OEM part number B-G9 directly. If your original cell is swelling, dropping charge fast, or refusing to hold voltage under screen or modem load, this is the swap.
- Nex 3 series compatibility: The Nex 3, Nex 3S 5G, and Nex 3 5G all share the same B-G9 footprint, connector pinout, and BMS handshake protocol. One cell fits across all three variants without modification.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on a Nex 3 unit. The BMS accepted the cell without error flags, and the charge IC stepped through trickle, CC, and CV phases cleanly to 4.40V cutoff.
- First-cycle fast charge handling: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell.
Why the Nex 3 reports wrong battery percentage after a cell swap
The Nex 3 uses a fuel gauge IC that builds a discharge model from the original cell's charge history. When you install a new cell, the IC is still running the old model — so the percentage it shows does not match actual cell voltage. This causes readings that jump, stall, or report full charge well before the cell reaches 4.40V. One complete slow discharge down to shutdown, followed by a full uninterrupted charge, resets the coulomb counter against the new cell's actual curve. After that cycle, percentage tracking aligns correctly.
Sudden shutdown at 20–30% on the replacement cell
This happens when the fuel gauge IC has not yet mapped the new cell's voltage cliff — the point where cell voltage drops sharply under load from the display or 5G modem. The phone still shows 20–30% but the cell voltage has already collapsed below the BMS cutoff threshold, typically around 3.2V under load. It is not a faulty cell — it is an uncalibrated gauge hitting a real voltage drop it did not predict. Run one full slow-charge cycle without fast charging enabled, then discharge the phone to automatic shutdown to force the IC to log the actual cliff point.