Oppo Reno 2 BLP735 Compatible Battery 3.85V 3900mAh

Oppo Reno 2 / Reno2 F — 3.85V Li-Polymer Replacement Battery (BLP735)

This is a 3900mAh (15.02Wh) lithium-polymer cell built to the BLP735 specification. It fits the Oppo Reno 2, Reno2 F, CPH1989, and CPH1907 handsets. Voltage is 3.85V nominal — the same rail the original cell runs on.

• Reno 2 / Reno2 F platform fit: Both handsets share the same battery bay geometry, connector pinout, and BMS handshake protocol. The CPH1989 and CPH1907 board revisions draw from the same voltage rail, so one cell specification covers all four models without modification.
• Bench tested on actual hardware: We cycled this cell through the Reno 2's charge IC under VOOC and standard 5V/2A input. The BMS accepted authentication on first insertion, the protection circuit held cutoff at the correct thresholds, and the fuel gauge IC began tracking state-of-charge without manual reset.
• First-cycle calibration on the Reno 2: On first use after installation, disable VOOC fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell — preventing early percentage-jump errors.

Sudden shutdown at 20–30% on the replacement cell

This happens because the fuel gauge IC is still running the discharge curve it learned from the old, degraded cell. When the new cell hits a section of its curve the IC hasn't mapped yet, the reported percentage doesn't match actual cell voltage. Under modem or display load, voltage sags briefly below the system cutoff threshold — the phone shuts down even though capacity remains. One full discharge to 0% followed by an uninterrupted charge to 100% forces the coulomb counter to re-anchor to the new cell's curve. After that cycle, shutdowns at 20–30% stop.

VOOC fast charge not activating after battery swap

Oppo's VOOC protocol requires the charge IC to complete a handshake with the battery's BMS before switching to high-current mode. On the first cycle after a cell swap, the IC defaults to standard 5V/2A while it verifies BMS parameters — this is normal behaviour, not a fault. If VOOC still fails to activate after the first full charge cycle, check that the battery connector is fully seated; a partially engaged pin breaks the data line the handshake runs on. Re-seat the connector and retry — VOOC should engage within 30 seconds of plugging in the original Oppo adapter.