BQ Aquaris X5 Compatible Battery 3.85V 2800mAh 2900

BQ Aquaris X5 — 3.85V Li-Polymer Replacement Battery (2900)

This 3.85V, 2800mAh (10.78Wh) Li-Polymer cell replaces the original battery in the BQ Aquaris X5 and Aquaris X5 Cyanogen Edition smartphones. It fits the same footprint as the OEM cell — 74.40 × 61.00 × 3.80 mm — and connects to the same flex ribbon on the motherboard. Swap it when the original cell no longer holds a charge or causes unexpected shutdowns.

• Aquaris X5 and X5 Cyanogen Edition fit: Both variants run the same battery bay dimensions and use the same connector pinout, so one cell covers both. The BMS handshake requirements are identical across the two firmware builds.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Aquaris X5 platform and confirmed the BMS accepted the cell without fault codes. The protection circuit responded correctly to over-charge and over-discharge thresholds.
• First-cycle fuel gauge reset: On first use after installation, disable fast charging and run one full discharge down to automatic shutdown, then charge uninterrupted to 100%. This gives the fuel gauge IC one clean reference cycle against the new cell's discharge curve before high-current charging begins.

Sudden shutdown at 20–30% on a freshly installed cell

A new cell has a different internal resistance profile than the aged cell the fuel gauge IC was calibrated to. Under modem radio or display load, the phone draws a short current spike that the voltage drops below the cutoff threshold — even though the reported percentage still shows charge remaining. The IC hasn't yet mapped the new cell's actual voltage cliff. One full discharge-to-shutdown followed by a full uninterrupted charge cycle recalibrates the coulomb counter and moves the cutoff trigger to the correct point on the new cell's curve.

Phone shows wrong percentage — jumping or stuck after battery replacement

The fuel gauge IC stores learned data from the old cell — its capacity curve, internal resistance, and self-discharge rate. A new cell invalidates that stored profile immediately, causing the percentage reading to jump, stick, or drop faster than actual charge consumed. The fix is a full calibration cycle: discharge the phone fully until it powers off on its own, then charge to 100% without interruption. After one complete cycle, percentage reporting should track accurately against the new cell.