LeTV LeEco Le 2 Replacement Battery LTF21A 3.83V 3000mAh

LeTV LeEco Le 2 / X620 / Le 2 Pro — 3.83V Li-Polymer Replacement Battery (LTF21A)

This is a 3000mAh (11.49Wh) lithium-polymer cell rated at 3.83V, built to fit the LeEco Le 2, Le 2 Pro, X620, and X520 series smartphones. It replaces OEM part number LTF21A. Fit these models when the original cell no longer holds voltage under screen or modem load.

• Le 2 / Le 2 Pro / X620 / X520 platform fit: These models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The 3.83V nominal voltage rail matches the charge IC on all listed variants — swapping between them does not require any firmware changes.
• Bench tested on actual hardware: We ran this cell through full charge-discharge cycles on a Le 2 unit. The BMS accepted the cell without error flags, charge termination triggered correctly at full capacity, and voltage held stable across high-draw screen-on and modem-active states.
• Fuel gauge recalibration on first use: After installation, disable fast charging and run one complete discharge down to auto-shutoff, then charge to 100% on standard current. This gives the fuel gauge IC one full cycle to map the new cell's discharge curve before fast-charge current is applied to an uncalibrated cell.

Why the Le 2 reports wrong battery percentage after a cell swap

The Le 2 uses a coulomb counter paired with a fuel gauge IC that builds its discharge model from the original cell's impedance and capacity curve. When you install a new cell, that stored model is still calibrated to the old, degraded battery. The gauge reads voltage and current against the wrong reference, so it reports inaccurate percentages — sometimes jumping 10–15% in either direction. One full discharge-charge cycle on standard charging rewrites the reference and corrects the readout.

Sudden shutdown at 20–30% on the replacement cell

This shutdown is a voltage cliff event, not a capacity problem. When the modem runs a data burst or the display hits peak brightness, instantaneous current draw spikes and pulls the cell voltage below the BMS cutoff threshold — even though the gauge still shows charge remaining. On a new cell before calibration, the fuel gauge IC does not yet know where that voltage cliff sits for this specific cell's internal resistance. Let the phone discharge naturally to auto-shutoff once, charge fully to 100%, and the BMS will map the cliff correctly. After that first full cycle, shutdowns at 20–30% should stop.