FiiO E10 Portable Amplifier Replacement Battery 3.7V 1400mAh

Fiio E10 / E10K / E11K — 3.7V Li-Polymer Replacement Battery (PL514746P 1S1P)

This 3.7V 1400mAh lithium-polymer cell replaces the internal battery in the Fiio E10, E10K, and E11K portable headphone amplifiers. All three models share the same battery footprint, connector pinout, and BMS handshake protocol. Capacity is 1400mAh (5.18Wh) — taken directly from product data, not estimated.

• E10, E10K, and E11K compatibility: These three models share a common PCB layout and draw from the same regulated 3.7V rail. The cell dimensions — 48.61 × 47.58 × 6.04mm — match the original battery bay without modification, and the BMS communicates charge state correctly to the on-board fuel gauge.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the E10K platform. The BMS accepted the cell without triggering a fault, regulated cutoff occurred at the correct low-voltage threshold, and the charge circuit brought the cell to full capacity without thermal event.
• First-cycle volume discipline: Run the amplifier at 50% volume for the first full charge cycle. Driving peak output from an uncalibrated cell pulls maximum current before the BMS has mapped the cell's actual delivery curve — that mismatch can cause an early protection trip and a false low-capacity reading on subsequent cycles.

Amp shutting off before the battery indicator reaches empty

The E10 and E10K use a fuel gauge that tracks charge state by voltage curve. When an aged or deeply discharged cell develops elevated internal resistance, its terminal voltage drops faster under load than the gauge expects. The amplifier's protection circuit sees that low voltage and cuts power — even though the displayed percentage still reads 20–30%. Fitting a fresh cell with low internal resistance restores the correct relationship between displayed charge and actual cutoff. After fitting the new cell, run two full discharge-to-cutoff cycles so the fuel gauge re-maps the curve accurately.

Clipping and distortion at moderate volume on a new battery

A new cell that hasn't completed its first calibration cycle can show voltage sag under the transient current spikes that audio amplification produces — particularly on bass-heavy tracks. That sag pulls the supply rail below the headroom the amplifier needs, causing the output stage to clip before the signal reaches its peak. This is not a fault in the amplifier or the cell. Running one full charge-and-discharge cycle at moderate volume lets the BMS calibrate the cell's internal resistance profile. After that cycle, voltage sag under load normalises and clipping resolves.