About this replacement
Vivo X70 Pro / V2105 — 3.87V Li-Polymer Replacement Battery (B-R6)
This is a 3.87V, 4350mAh Li-Polymer cell that replaces the original B-R6 battery in the Vivo X70 Pro, X70 Pro 5G, and V2105. It fits the same footprint at 75.10 × 62.34 × 5.00mm and connects to the same charge IC and fuel gauge already on the board. Swap this in when the original cell no longer holds voltage under display or modem load.
- X70 Pro and V2105 fitment: Both the X70 Pro and V2105 share the same PCB layout, connector position, and BMS handshake protocol — that is why a single B-R6 cell covers all three model variants without modification.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge on the X70 Pro board, confirmed BMS communication remained stable across the complete voltage window from 4.40V down to 3.00V, and verified the charge IC accepted the cell without triggering a fault flag.
- Fuel gauge recalibration on first use: 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 runs against an uncalibrated coulomb counter.
Sudden shutdown at 20–30% on the replacement cell
This happens because the fuel gauge IC is still referencing the discharge curve of the old, degraded cell. When the new cell's actual voltage drops under modem or display load, the IC misreads remaining capacity and triggers a low-voltage shutdown earlier than the percentage shown. The fix is one full uninterrupted discharge to 0% followed by a complete charge to 100% with fast charging off. After that cycle, the coulomb counter resets against the new cell's curve and shutdowns at false percentages stop.
USB-PD fast charge not accepted on the first cycle after replacement
On the first charge after a cell swap, Vivo's proprietary charge protocol may not handshake correctly between the charger and the new cell's BMS. The phone falls back to standard 5V charging as a safety default. This is not a fault with the cell — the BMS needs one standard charge cycle to initialise communication with the charge IC. Plug in using the original Vivo charger, let the first cycle complete at standard rate, and fast charging resumes on the next plug-in.