Sony NW-E403 Replacement Battery 3.7V 330mAh Li-Polymer

Sony NW-E403 / NW-E405 / NW-E407 / NW-E503 — 3.7V Li-Polymer Replacement Battery (1-175-558-11)

This is a 3.7V, 330mAh Li-Polymer battery for the Sony NW-E403, NW-E405, NW-E407, and NW-E503 digital audio players. It replaces OEM part numbers 1-175-558-11 and MR11-2788. Fit the same slim 54.19 × 23.76 × 3.89mm cell into the original housing — no modification needed.

• NW-E400 and NW-E500 series compatibility: These models share the same cell footprint, connector orientation, and BMS voltage thresholds. Sony used one battery platform across both series, so the same 3.7V cell handles the charge circuit on all listed units without triggering a protection fault.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the NW-E403 platform. The BMS accepted full charge termination at 4.2V and held the low-voltage cutoff at approximately 3.0V without tripping the protection circuit prematurely.
• First charge after a cell swap: After installing a new cell, connect the player to USB power before pressing the power button. If the old cell had been deeply discharged, the device may show no response — leave it on charge for at least 30 minutes to allow the protection circuit to exit its locked state before attempting to power on.

Battery percentage jumping after a cell swap on the NW-E403

Sony's NW-E series reads battery state using a voltage-threshold lookup table stored in firmware. After replacing the cell, that table is calibrated against the old cell's discharge curve, not the new one. For the first few charge cycles, the displayed percentage will jump — often dropping from 80% to 20% in a short span. Run three full charge and discharge cycles back to back to let the firmware re-anchor its reference points to the new cell's actual voltage behaviour.

Playback cutting out before the battery indicator shows empty

The audio amplifier inside the NW-E series draws a short current spike each time it drives the output stage. At the tail end of a discharge curve — typically below 3.3V — the cell's internal resistance rises enough that this spike causes a momentary voltage sag below the amplifier's operating floor. The firmware reads this as a fault and shuts down playback, even though the indicator still shows remaining charge. The fix is to charge the battery back to 4.2V and run the three-cycle recalibration so the firmware learns where the real cutoff sits on this cell.