BLP787 Oppo Reno4 Pro 4G Replacement Battery 7.74V 2000mAh

Oppo Reno4 Pro 4G / CPH2109 — 7.74V Li-Polymer Replacement Battery (BLP787)

This is a 7.74V, 2000mAh Li-Polymer replacement battery for the Oppo Reno4 Pro 4G (CPH2109). It replaces OEM part BLP787 and fits directly into the Reno4 Pro 4G battery bay. When the original cell degrades — losing charge capacity or failing to hold voltage under load — this swap restores normal operation.

• Reno4 Pro 4G / CPH2109 fit: Both model designations share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The BLP787 footprint at 86.75 × 61.55 × 4.70mm matches the original cell exactly — no bracket modifications needed.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on a CPH2109 unit. The BMS accepted the new cell without error flags, and the fuel gauge IC tracked state-of-charge through the full voltage window from 8.7V down to the 6.0V cutoff.
• First-cycle fast charge protocol: On first use after installation, disable VOOC 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 amperage into an uncalibrated cell.

Sudden shutdown at 20–30% on the Reno4 Pro 4G after a cell swap

The Reno4 Pro 4G uses a coulomb-counter fuel gauge that was calibrated to the original cell's discharge curve. After a cell swap, the counter still references the old curve — so when the new cell hits a voltage cliff under modem or screen load, the phone shuts down even though the reported percentage looks safe. The fix is one full discharge-to-cutoff followed by a full charge, with VOOC disabled. After that cycle, the fuel gauge IC maps the new cell's actual voltage curve and percentage reporting stabilises.

VOOC fast charge not activating on the first cycle after replacement

Oppo's VOOC protocol requires a handshake between the charge IC, BMS, and charger before high-current delivery begins. On a freshly installed cell, the BMS may not complete that handshake on the first cycle — the phone drops back to standard 5V/1A charging instead. This is not a fault. Complete one full standard-charge cycle, allow the phone to reach 100% and sit for two minutes, then reconnect the VOOC charger. The handshake completes and fast charging activates at that point.