OPPO A78 4G BLPA07 Replacement Battery 3.87V 5000mAh

Oppo A78 4G / CPH2565 — 3.87V Li-Polymer Replacement Battery (BLPA07)

This is a 3.87V, 5000mAh Li-Polymer replacement battery for the Oppo A78 4G (CPH2565). It replaces OEM part number BLPA07 directly. Rated at 19.35Wh, it matches the original cell's capacity and voltage rail for this handset.

• A78 4G and CPH2565 fitment: Both model references point to the same hardware revision — same connector pinout, same BMS handshake protocol, same physical cell dimensions. One battery covers both listings without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the A78 4G platform. The BMS accepted charging on the first connection, protection circuits triggered correctly at low-voltage cutoff, and the fuel gauge IC registered the full 5000mAh cell without throwing calibration errors.
• Fuel gauge recalibration after install: On first use, disable fast charging and run one complete discharge-charge cycle at standard rate. The fuel gauge IC on the A78 4G calibrates its coulomb counter against the cell's actual discharge curve — skipping this step with fast charge active can push current into an uncalibrated cell and leave the percentage readout misaligned for weeks.

Sudden shutdown at 20–30% on the Oppo A78 4G after a cell swap

This happens when the fuel gauge IC is still mapped to the old cell's discharge curve. The new cell hits a voltage cliff — the point where output voltage drops sharply under modem or screen load — at a different state of charge than the original. The phone's protection circuit reads that voltage drop as critically low and shuts down, even though the percentage display showed charge remaining. One full slow-charge cycle resets the coulomb counter and shifts the shutdown threshold to match the new cell's actual curve.

USB fast charge not activating on the first cycle after replacement

After installing a new cell, the charge IC may default to a trickle or standard charge rate on the first cycle. This is a BMS precaution — the controller has no stored data on the new cell's impedance and holds back high-current charging until it has baseline readings. Plug in via the original cable and charger, let the first cycle complete fully without interruption, and fast charge should re-engage from the second cycle onward. If it still doesn't activate, check that the USB-C port pins are clean — a dirty port blocks the handshake signal the fast charge protocol depends on.