BLP737 Oppo Reno2 Z Replacement Battery 3.85V 3900mAh

Oppo Reno2 Z — 3.85V Li-Polymer Replacement Battery (BLP737)

This is a 3.85V, 3900mAh Li-Polymer replacement cell for the Oppo Reno2 Z smartphone, covering model numbers PCKM80, CPH1945, and CPH1951. It slots into the same physical bay as the original BLP737 and connects to the same charge IC and fuel gauge circuit. Capacity is 15.02Wh — matched to the original specification.

• Reno2 Z platform fit (PCKM80 / CPH1945 / CPH1951): These three model numbers share the same mainboard layout, connector pinout, and BMS handshake protocol. A single BLP737 cell covers all three without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Reno2 Z mainboard. The BMS accepted the cell without error flags, and the charge IC stepped through trickle, constant-current, and constant-voltage phases cleanly.
• First-cycle fast charge protocol: On first use after installation, disable VOOC fast charging for one complete discharge-to-charge cycle. The fuel gauge IC needs to map the new cell's discharge curve before high-current charging is applied to an uncalibrated cell. Re-enable fast charge on the second cycle.

Sudden shutdown at 20–30% on the Reno2 Z after a cell swap

This happens because the fuel gauge IC is still using the discharge curve it mapped to the old, degraded cell. When the new cell hits a load spike — from the modem, screen, or GPS — voltage drops briefly below the BMS cutoff threshold even though the reported percentage looks safe. The phone shuts down to protect the circuit, not because the cell is faulty. One full discharge down to automatic shutdown followed by an uninterrupted charge to 100% lets the coulomb counter recalibrate against the new cell's actual voltage curve. After that cycle, shutdowns at 20–30% typically stop.

Battery percentage jumping erratically after replacement

Erratic percentage readings — jumping from 45% to 60% or dropping ten points in seconds — come from the fuel gauge IC comparing live cell voltage against a learned model that no longer matches the installed cell. The IC accumulated that model over months with the original cell and cannot instantly relearn it. Force a full discharge until the phone powers off on its own, then charge without interruption to 100%. If jumps persist after two cycles, check that the battery connector is fully seated — an intermittent contact causes voltage read errors that look identical to a calibration fault.