BLP803 Oppo Realme V3 Replacement Battery 3.87V 4900mAh

Oppo Realme V3 — 3.87V Li-Polymer Replacement Battery (BLP803)

This is a 3.87V, 4900mAh lithium-polymer cell built to the BLP803 specification for the Oppo Realme V3 smartphone. It replaces the original cell when capacity has dropped, the phone shuts off unexpectedly, or the battery no longer holds a usable charge. At 18.96Wh, it matches the factory energy rating for this handset.

• Realme V3 fit confirmation: The BLP803 uses a fixed connector pinout and cell footprint (89.00 × 63.70 × 4.70mm) specific to the Realme V3 chassis. The BMS communicates directly with the phone's charge IC over the same data line as the factory cell — no adapter required.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Realme V3 unit. The BMS accepted the USB charge handshake correctly, protection circuitry tripped at expected over-voltage thresholds, and the fuel gauge IC began tracking state-of-charge accurately after one full cycle.
• First-cycle fast charge protocol: 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 current into an uncalibrated cell.

Why the Realme V3 reports wrong battery percentage after a cell swap

The Realme V3 uses a fuel gauge IC that builds a discharge model over time against the original cell. When a new cell goes in, the IC is still referencing the old cell's internal resistance curve and capacity map. The percentage shown on screen reflects that stale model, not the actual state-of-charge of the new cell. One full discharge to below 10% followed by a complete uninterrupted charge to 100% forces the IC to reset its coulomb counter and begin building an accurate model against the new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under peak load — typically when the modem transmits data or the display drives full brightness simultaneously. A fresh cell with an uncalibrated fuel gauge will show 25% on screen while actual cell voltage has already fallen below the 3.4V cutoff threshold. The BMS interprets this as a fault and kills power before the display can update. Complete one full discharge-to-charge calibration cycle first, then check whether shutdowns persist — if they do at the same percentage, confirm the phone's charge IC is not holding a cached battery profile from Settings.