BQ Strike Selfie Max 3.85V Replacement Battery BQ-5504 2900mAh

BQ Strike Selfie Max — 3.85V Li-Polymer Replacement Battery (BQ-5504)

This is a 3.85V, 2900mAh Li-Polymer replacement battery for the BQ Strike Selfie Max (BQ-5504). It fits directly into the BQ-5504 handset and restores power to the phone's core functions — calls, apps, and the front-facing selfie camera system. Capacity figure is 2900mAh / 11.17Wh as specified for this cell.

• BQ-5504 platform fit: The Strike Selfie Max uses a fixed Li-Polymer cell with a dedicated connector pinout and BMS handshake tied to the BQ-5504 board. This replacement matches that voltage rail and connector, so the charge IC communicates with the cell without throwing a fault.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the BQ-5504 board. The BMS accepted the cell on first connect, charge termination triggered correctly at full voltage, and the fuel gauge IC read a stable state-of-charge without resetting mid-cycle.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one full discharge-to-charge cycle at standard current. This lets the fuel gauge IC map the new cell's discharge curve before the OS starts reporting percentage — skipping this step causes erratic percentage readings in the first few days.

Sudden shutdown at 20–30% on the BQ-5504 after a cell swap

This happens because the fuel gauge IC is still calibrated to the old cell's discharge curve. The replacement cell hits a voltage cliff — often around 3.6V under modem or screen load — before the gauge reaches zero. The phone's protection circuit cuts power to prevent over-discharge, but the OS reports it as a shutdown at 20–30%. One full discharge cycle from 100% down to automatic cutoff, then a full charge without interruption, gives the coulomb counter enough data to recalibrate to the new cell.

Phone warm near the battery during the first few charges after replacement

A new Li-Polymer cell has higher internal impedance than a broken-in cell. During the first few charge cycles, the charge IC works against that resistance, which generates more heat than normal. This is not a fault — impedance drops as the cell cycles and heat levels off. If the phone stays warm past the third full charge, check that the charge port is clean and the cable is delivering the correct voltage; a marginal cable forces the charge IC to draw more current to compensate.