BLU Life 8 XL Compatible Battery C836404292L 3.8V 3000mAh

BLU Life 8 XL / L290U — 3.8V Li-Polymer Replacement Battery (C836404292L)

This 3.8V, 3000mAh (11.4Wh) lithium-polymer cell replaces the original C836404292L battery in the BLU Life 8 XL and L290U smartphones. It slots into the same battery bay and connects to the same charge IC and fuel gauge circuit. Dimensions are 83.05 × 63.90 × 4.20mm — verify yours before ordering.

• Life 8 XL and L290U fit: Both model variants share the same battery bay geometry, connector pinout, and BMS handshake protocol — one cell covers both. The C836404292L part number appears on both original units.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the L290U platform. The BMS accepted the full charge cycle without tripping overcurrent protection, and the fuel gauge IC tracked state of charge without flagging a mismatch fault.
• First-cycle fast charge note: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard rate. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before high-current charging is applied to an uncalibrated cell.

Sudden shutdown at 20–30% on the BLU Life 8 XL after a cell swap

A new lithium-polymer cell has a slightly different voltage-versus-capacity curve than the worn cell the fuel gauge IC was calibrated to. When the phone hits a load spike — modem transmit, screen brightness burst — the cell voltage drops faster than the IC expects and the protection circuit cuts output before the displayed percentage reaches zero. This is a calibration gap, not a faulty battery. Run two full discharge-charge cycles without fast charging and the coulomb counter will map the new curve accurately.

Phone won't power on after the replacement cell sat in storage

Lithium-polymer cells self-discharge during storage. If the cell voltage has dropped below approximately 2.5V, the BMS enters lockout mode and blocks all charge current to prevent cell damage. The phone will show no charge indicator and will not respond to the power button. Connect the phone to a wall adapter — not a USB port — and leave it for 20–30 minutes without pressing anything. The charge IC will trickle current into the cell until voltage climbs above the BMS re-enable threshold, typically around 2.8–3.0V, at which point normal charging resumes.