About this replacement
Oppo R11S — 3.85V Li-Polymer Replacement Battery (BLP643)
This is a 3.85V, 3000mAh Li-Polymer cell built to the BLP643 specification. It fits the Oppo R11S, R11st, R11s Dual SIM, and R11s Dual SIM TD-LTE. Swap it in when the original cell no longer carries the phone through a normal day.
- R11S variant compatibility: The R11S, R11st, and both Dual SIM variants share the same 81.45 × 58.74 × 3.60mm cell bay, the same BLP643 connector, and the same BMS handshake line. One cell covers all four models without any adapter or wiring change.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the R11S mainboard. The BMS accepted the handshake on first connection, the charge IC ramped normally, and no protection trips fired during the discharge sweep.
- Fuel gauge recalibration on first use: After installation, disable VOOC 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 actual discharge curve before high-current charging begins on an uncalibrated cell.
Why the R11S reports wrong battery percentage after a cell swap
The R11S uses a coulomb-counter fuel gauge IC that stores a learned discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches the new cell's actual voltage-to-capacity profile. The gauge reads off an old map, so it can report 40% while the real state of charge is lower. One complete discharge down to auto-shutdown followed by a full charge resets the learned curve to the new cell.
Sudden shutdown at 20–30% on the replacement cell
This happens when the modem or display pulls a current spike that the cell cannot sustain without a voltage sag below the BMS cutoff threshold. The gauge still shows 20–30% because the coulomb counter hasn't recalibrated yet, but the cell voltage drops under load and the BMS trips. It is not a faulty cell — it is an uncalibrated gauge masking a real low-charge condition. Run two full discharge-charge cycles and verify the resting voltage sits at or above 3.85V before trusting the percentage readout.