BLU Energy X2 C906052400L Replacement Battery 3.8V 2900mAh

BLU Energy X2 — 3.8V Li-ion Replacement Battery (C906052400L)

This is a 3.8V, 2900mAh lithium-ion battery for the BLU Energy X2 smartphone (models E050 and E050U). It replaces part number C906052400L directly. Dimensions are 89.66 × 59.90 × 4.60mm — measure your original before fitting if you are unsure.

• Energy X2 / E050 / E050U compatibility: All three model numbers reference the same hardware platform. They share an identical battery bay, connector pinout, and BMS handshake protocol — one cell fits all three without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the Energy X2 platform. The BMS accepted the cell, thermistor readings stayed within spec, and the charge IC completed full cycles without cutoff errors.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This gives the fuel gauge IC time to recalibrate against the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell.

Why the Energy X2 reports wrong battery percentage after a cell swap

The fuel gauge IC on the Energy X2 builds its charge model from the discharge curve of the original cell. When a new cell goes in, that stored curve no longer matches the physical cell's actual voltage-to-capacity relationship. The IC reads voltage and maps it against the old model, so the percentage shown on screen is off. One full discharge down to auto-shutoff and a complete recharge resets the coulomb counter and rebuilds an accurate curve for the new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below the modem or display's minimum rail voltage under load — even though the fuel gauge still shows charge remaining. The old fuel gauge model predicts a gentle voltage slope, but the new cell hits a steeper voltage cliff at low state-of-charge. The phone cuts out before the gauge reaches zero. Run two full discharge-recharge cycles without fast charging; once the fuel gauge IC recalibrates, the shutoff threshold aligns correctly and the premature cutoff stops.