Vivo BA45 V2318A Replacement Battery 3.91V 5850mAh

Vivo Y36 5G / Y36i 5G / Y28 — 3.91V Li-Polymer Replacement Battery (BA45)

This is the BA45 lithium-polymer battery for the Vivo V2318A, Y28, Y36 5G, and Y36i 5G. It runs at 3.91V with a capacity of 5850mAh (22.87Wh). If your original cell is swelling, losing charge rapidly, or refusing to power the device, this is the direct cell replacement.

• V2318A / Y28 / Y36 5G / Y36i 5G platform fit: These four models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — all validated against the BA45 part number. Swapping between models on this platform does not require firmware changes.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Y36 5G unit. The BMS accepted the cell without error flags, charge current ramped normally through CC/CV stages, and protection circuitry tripped correctly at the expected low-voltage cutoff threshold.
• Fuel gauge recalibration on first use: After installation, disable fast charging and run one full discharge-to-charge cycle at standard current. This lets the fuel gauge IC map its coulomb counter against the new cell's discharge curve before high-current charging loads an uncalibrated cell.

Sudden shutdown at 20–30% on the Y36 5G after a cell swap

This happens because the fuel gauge IC still holds the discharge curve of the old, degraded cell. When the new cell hits a voltage point that mapped to 20–30% on the worn cell, the OS reads it as near-empty and triggers a protective shutdown. The phone still has usable charge — the gauge is just wrong. One complete discharge cycle down to automatic cutoff, followed by a full charge, forces the coulomb counter to resync to the new cell. After that cycle, percentage reporting stabilises.

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

On the first charge after a cell swap, Vivo's charge IC runs a brief cell-validation handshake before enabling the high-current fast charge path. If the BMS on the replacement cell hasn't completed that handshake, the charger falls back to standard 5V input. This is not a fault — it resolves after the first full charge cycle completes. Plug into the original Vivo charger for the first cycle; third-party chargers that negotiate voltage before the handshake finishes can extend the delay.