Wiko ROBBY 2 Replacement Battery 3.8V 2600mAh

Wiko ROBBY 2 — 3.8V Li-ion Replacement Battery (3921)

This is a 3.8V, 2600mAh Li-ion cell that replaces the original battery in the Wiko ROBBY 2 smartphone. It uses OEM part number 3921 and fits the ROBBY 2 directly. Capacity figures are taken from the product data — 9.88Wh total energy.

• ROBBY 2 fitment: The ROBBY 2 uses a removable rear-access cell with a standardised connector and BMS contact pad layout. This replacement matches that connector pinout and communicates with the phone's charge IC and fuel gauge IC without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the bench. The BMS accepted charge input correctly, cutoff triggered at the expected low-voltage threshold, and the cell held voltage under simulated load without drop-out.
• 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 recalibrate against the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell.

Why the ROBBY 2 reports wrong battery percentage after a cell swap

The ROBBY 2's fuel gauge IC builds a model of the cell based on charge and discharge history. When you swap in a new cell, that stored model no longer matches the new cell's actual voltage curve. The OS reads from the old model, so percentage shown can be 10–20% off from real state of charge. One full discharge to auto-shutdown followed by an uninterrupted charge to 100% resets the coulomb counter and corrects this.

Sudden shutdown at 20–30% remaining on the replacement cell

This happens when the fuel gauge IC has not yet recalibrated to the new cell's discharge curve. The phone calculates remaining charge from the old curve, so it still shows 25% while the actual cell voltage has already dropped below the modem's minimum operating threshold. Under a burst load — a call, screen-on, or background data sync — the voltage sags further and the protection circuit trips. Run one full cycle without fast charging first; if the issue persists after two full cycles, check that the cell connector is seated flat and the contact pads are making clean contact.