Realme Q5 BLP965 Replacement Battery 3.87V 4800mAh

Realme Q5 / RMX3478 — 3.87V Li-Polymer Replacement Battery (BLP965)

The BLP965 is the OEM-matched lithium-polymer cell for the Realme Q5 (RMX3478) smartphone. It runs at 3.87V nominal and delivers 4800mAh (18.58Wh) of capacity. This battery fits the Q5 body cavity at 93.80 × 64.40 × 4.50mm with the original flex connector.

• Q5 and RMX3478 platform fit: Both model designations refer to the same hardware board. The connector pinout, BMS handshake voltage, and charge-termination threshold are identical across both variants, so one cell covers the full Q5 line.
• Bench tested on actual hardware: We cycled the BLP965 through charge and discharge on the Q5 board. The BMS accepted the cell without triggering a thermal fault, and the charge IC reached full termination at 4.40V as expected for this platform.
• Fuel gauge recalibration on first use: Disable fast charging for the first complete discharge-charge cycle after fitting this cell. The fuel gauge IC uses coulomb counting calibrated to the old cell's discharge curve. One full slow cycle lets it reset against the new cell before high-current charging begins.

Sudden shutdown at 20–30% on the Realme Q5 after a cell swap

The Q5 fuel gauge IC holds a learned discharge curve from the previous cell. When the new BLP965 cell hits a voltage point the IC hasn't mapped yet, the system reads remaining capacity as zero and cuts power — even though charge is still present. This is not a faulty cell. Running one full discharge to shutdown and a complete slow charge resets the coulomb counter and maps the new cell's actual voltage cliff. After that cycle, shutdown behaviour returns to normal.

USB-PD fast charge not accepted on the first cycle after replacement

On first connection after fitting the BLP965, the charge IC may reject the fast-charge handshake and fall back to standard 5V charging. This happens because the BMS on a fresh cell starts conservative until it has confirmed cell impedance is within range. Charge the phone once at standard speed using the supplied cable and a basic 5W charger. On the second cycle, plug in the fast charger — the BMS will have cleared its initialisation flag and the full charge rate will resume.