About this replacement
Oppo A36 / PESM10 — 3.87V Li-Polymer Replacement Battery (BLP879)
This is a 3.87V, 4850mAh Li-Polymer cell built to the BLP879 spec for the Oppo A36 and PESM10. It replaces a degraded or failed original battery in this mid-range Android handset. Capacity figure comes from product data — 18.77Wh total energy.
- A36 and PESM10 compatibility: Both model numbers reference the same hardware platform — same connector pinout, same BMS handshake protocol, same charge IC voltage rails. One cell fits both without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the A36 platform. The BMS accepted the cell without fault codes, and the charge IC stepped through trickle, CC, and CV phases cleanly on the first cycle.
- First-cycle fast charge hold-off: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before high-current charging pushes rate into an uncalibrated cell — preventing early percentage drift.
Why the Oppo A36 reports wrong battery percentage after a cell swap
The fuel gauge IC stores a discharge curve mapped to the original cell's impedance profile. When you swap in a new cell, the stored curve no longer matches the actual cell chemistry, so percentage readings drift — often reading high early in discharge, then dropping fast near the bottom. The fix is one full uninterrupted discharge down to auto-shutoff, followed by a full charge to 100% with fast charging disabled. After that cycle, the coulomb counter resets its baseline to the new cell. Percentage accuracy stabilises within two or three further cycles.
Sudden shutdown at 20–30% after fitting the BLP879
This happens when the modem, display, or both pull a current spike the cell can't sustain at that state of charge — voltage sags below the BMS cutoff threshold before the percentage reading has caught up. It's a calibration gap, not a faulty cell. Run that first full discharge-to-shutoff cycle with fast charging off, then charge fully. If shutdown continues past three cycles, check that the replacement cell connector is fully seated — a partially engaged connector raises contact resistance and worsens voltage sag under load. Target a resting voltage of 3.87V at full charge after calibration.