About this replacement
Fiio E5 / E3 / E6 — 3.7V Li-Polymer Replacement Battery (PL402030 1S1P)
This 3.7V, 190mAh Li-Polymer cell replaces the original PL402030 1S1P battery inside the Fiio E5, E3, and E6 portable headphone amplifiers. It fits the compact PCB stack in all three units, which share the same battery bay dimensions and connector. Capacity figure is 190mAh (0.7Wh) — use that number when comparing cells.
- E5 / E3 / E6 shared platform: All three models use the same battery footprint, voltage rail, and protection circuit handshake. One cell covers the full lineup without modification to the connector or housing.
- Bench tested on actual hardware: We ran this cell on an E5 unit and confirmed the onboard BMS accepted charge without tripping, held the 3.7V nominal rail through a full discharge curve, and released cleanly at the low-voltage cutoff.
- First-cycle volume discipline: Run the amplifier at 50% volume for the entire first charge cycle. Full-volume operation on an uncalibrated cell draws peak current before the cell has established its delivery baseline, which can cause the BMS to trip early and misread remaining capacity on all future cycles.
Amp shutting off before the battery indicator reaches empty
The E5 amplifier circuit requires a minimum supply voltage slightly above the point where the LED indicator changes state. When a degraded or new-but-uncalibrated cell develops voltage sag under audio load, the amp hits its cutoff threshold while the indicator still shows charge remaining. The fix is a full uninterrupted charge to 4.2V followed by a controlled discharge at low-to-moderate volume — this lets the protection circuit relearn the cell's actual delivery curve. After two or three of these cycles, the cutoff and indicator should align within normal tolerance.
Clipping and distortion at moderate volume on a freshly installed cell
Clipping on a new cell usually points to a calibration gap, not a faulty battery. The amplifier's output stage draws bursts of current during transient peaks in audio — if the cell's protection circuit hasn't yet mapped its internal resistance, those bursts cause a momentary voltage drop that clips the output waveform. Running two full charge-discharge cycles at 50–70% volume stabilises the cell's internal resistance reading inside the BMS. If clipping persists past three cycles at a steady 3.7V supply, check the solder joint on the battery connector before suspecting the cell itself.