BLU Energy X LTE E0010UU Replacement Battery BL-N4000 3.8V

BLU Energy X LTE E0010UU — 3.8V Li-Polymer Replacement Battery (BL-N4000)

This is a 3.8V, 4000mAh Li-Polymer replacement battery for the BLU Energy X LTE E0010UU smartphone. It carries OEM part number BL-N4000 and matches the original cell's physical dimensions at 100.40 × 67.20 × 4.60 mm. It replaces a degraded or capacity-faded original cell in this specific handset.

• Energy X LTE E0010UU fit: The E0010UU uses a removable Li-Polymer cell on a 3.8V nominal rail. The BL-N4000 part number matches the connector pinout and BMS handshake expected by this phone's charge IC — no other BLU Energy variant shares this exact footprint and part number.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the E0010UU platform. The BMS accepted the cell without fault flags, charge termination triggered correctly at 4.35V, and low-voltage cutoff engaged at the expected floor.
• Fuel gauge recalibration on first use: On the first installation, disable fast charging and run one full discharge-to-charge cycle at standard current. This lets the phone's fuel gauge IC map the new cell's discharge curve before coulomb-counting under high-current fast charge input into an uncalibrated cell.

Sudden shutdown at 20–30% on the BL-N4000 after installation

The E0010UU's fuel gauge IC retains the discharge curve from the old, degraded cell. When the replacement cell hits a voltage point the IC associates with a higher state of charge, the phone reads more capacity remaining than actually exists under load. The modem or display then pulls current, voltage drops sharply below the cutoff floor, and the phone shuts off — sometimes at a reported 25%. One complete discharge cycle from 100% to automatic shutdown, followed by a full charge, forces the IC to recalibrate against the new cell. After that cycle, percentage readings stabilise.

USB fast charge not activating after swapping the BL-N4000

On the first charge cycle after a cell swap, some charge ICs on the E0010UU default to standard 5V/1A input instead of negotiating a higher-power profile. This happens because the BMS on the new cell has not yet completed its initialisation handshake with the phone's charge controller. Plug in using the original cable and charger, leave the phone untouched for a full charge cycle, then disconnect and reconnect. Fast charge negotiation resumes normally from the second cycle onward.