About this replacement
Oppo R9s Plus — 3.85V Li-Polymer Replacement Battery (BLP623)
This is a 3.85V, 4000mAh Li-Polymer replacement battery for the Oppo R9s Plus smartphone. It fits the R9s Plus, R9s Plus Dual SIM, R9s Plus Dual SIM TD-LTE, and CPH1611, among other variants sharing the BLP623 cell. Swap it when the original cell no longer holds charge or causes unexpected shutdowns.
- R9s Plus variant compatibility: The single-SIM, Dual SIM, and TD-LTE variants all draw from the same 3.85V power rail and use identical BLP623 connectors with the same BMS handshake — one cell covers all of them.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on R9s Plus hardware. The BMS accepted the cell without fault codes, and the charge IC handed off to trickle mode correctly at full capacity.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This allows the fuel gauge IC to map the new cell's discharge curve before high-current charging pushes into an uncalibrated state.
Why the R9s Plus reports wrong battery percentage after a cell swap
The R9s Plus uses a coulomb counter IC that builds its reference model from the original cell's charge and discharge history. When a new cell goes in, that reference is stale. The IC reads voltage and calculates state-of-charge against the old curve, so the displayed percentage drifts from actual capacity. One full discharge to auto-shutdown followed by a complete charge to 100% forces the IC to relearn the new cell's curve and corrects the readout.
Sudden shutdown at 20–30% on the replacement cell
This happens when the modem, display, or both pull a current spike the cell can't sustain at that state-of-charge. Voltage drops sharply below the BMS cutoff threshold — typically around 3.2V per cell — and the phone shuts off despite the gauge showing charge remaining. It is most common in the first few cycles before the fuel gauge IC recalibrates. Run two full discharge-charge cycles without fast charging and confirm the gauge tracks correctly before treating the cell as faulty.