Oppo A77 BLP631 Replacement Battery 3.85V 3200mAh

Oppo A77 / F1s — 3.85V Li-Polymer Replacement Battery (BLP631)

This is a 3200mAh, 3.85V Li-Polymer replacement battery for the Oppo A77, F1s 2017 Dual SIM LTE, F1s Global Dual SIM TD-LTE 64GB, and related A77 Dual SIM variants. It replaces OEM part number BLP631. Swap it in when the original cell degrades, fails to hold charge, or won't take a charge at all.

• A77 and F1s platform compatibility: These models share the same physical cell format, connector pinout, and BMS handshake protocol. The BLP631 cell fits the same battery bay across the full variant lineup — 32GB and 64GB storage tiers included — because Oppo used a single power platform across this generation.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on A77 hardware and confirmed the BMS handshake with the charge IC. The protection circuit responds correctly to overvoltage and thermal events, and the fuel gauge IC begins calibration on the first full cycle.
• First-cycle fast charge protocol: On first use after installation, disable VOOC or 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 — preventing early percentage drift and thermal spikes.

Sudden shutdown at 20–30% on the Oppo A77 after a cell swap

The A77's fuel gauge IC stores a charge curve calibrated to the old cell. When a new BLP631 cell goes in, the IC maps voltage readings to the old curve — and at around 3.6–3.7V, where older cells were nearly flat, the new cell still has usable capacity. The phone cuts power because it thinks the cell is at 0% when it isn't. Running two full discharge-charge cycles without fast charging forces the coulomb counter to rebuild its model against the actual cell. After that, the percentage readout stabilises and the shutdowns stop.

Phone feels warm near the battery bay during first few charges

A fresh Li-Polymer cell has slightly higher internal impedance than a broken-in cell. The charge IC on the A77 pushes current at the same rate it used with the old cell, which generates more heat across a higher-impedance cell during CC phase. This is normal for the first three to five charge cycles as the cell's impedance drops toward its rated value. If warmth persists beyond five cycles or the phone becomes hot to the touch, check that the replacement cell is seated flat with no gap at the battery connector — a loose connector increases contact resistance and compounds heat generation.