About this replacement
Vivo V40 5G / V2348 — 3.87V Li-Polymer Replacement Battery (BA49)
This is a 3.87V, 5350mAh (20.7Wh) Li-Polymer replacement battery carrying OEM part number BA49. It fits the Vivo V2348 and V40 5G smartphones. Replace it when the original cell no longer holds a full charge, swells, or causes unexpected shutdowns.
- V2348 and V40 5G compatibility: Both models share the same battery bay dimensions, connector pinout, and BMS communication protocol — that is why BA49 covers both. The fuel gauge IC handshake is identical across this hardware revision.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge on a V40 5G unit. The BMS accepted the cell without error flags, and the charge IC handed off to trickle correctly at 4.38V terminal voltage.
- Fuel gauge recalibration on first cycle: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes amperage into an uncalibrated coulomb counter.
Sudden shutdown at 20–30% on the replacement cell
This happens because the fuel gauge IC is still running a calibration curve built from the old degraded cell. The new cell has a steeper voltage cliff under modem and display load than the counter expects. The phone interprets that voltage dip as a deeper discharge than the percentage shown and triggers a protective shutdown. Run one full discharge to auto-off followed by an uninterrupted charge to 100% to let the coulomb counter reset against the new cell's actual curve.
USB-PD fast charge not working on the first cycle after swap
On the first charge cycle with a new cell, the BMS may reject the handshake for high-current charging protocols until it has confirmed cell impedance is within range. The charge IC defaults to a lower constant-current rate as a safety measure. This is not a fault — it clears after one standard charge cycle completes. Plug into a standard 5V/2A charger for the first full cycle, then reconnect your fast charger on the second cycle.