Sony NW-E435 Replacement Battery 3.7V 570mAh 1-756-819-11

Sony NW-E435 / NWZ-E436 Series — 3.7V Li-Polymer Replacement Battery (1-756-819-11)

This is a 3.7V 570mAh Li-Polymer battery for the Sony NW-E435, NW-E435F, SOK-NWZ-E435F(B), and NWZ-E436 Walkman digital audio players. It replaces OEM part number 1-756-819-11. The slim 3.56mm cell profile matches the original and fits the device's tight internal cavity without modification.

• NW-E435 and NWZ-E436 platform fit: These models share the same 3.7V single-cell architecture, connector pinout, and BMS handshake protocol. One cell covers the full listed range without any wiring or adapter changes.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the NW-E435 platform. The BMS accepted the cell without error flags, and the charge controller stepped through the expected constant-current and constant-voltage phases cleanly.
• First-charge protocol after cell swap: After installing a new cell, connect the player to a charger before attempting to power on. Media players in this series often enter a deep-discharge protection state during storage, which requires a slow trickle charge — sometimes 20 to 30 minutes — before the device accepts a normal charge current and responds to the power button.

Battery percentage jumping erratically after cell swap

The NW-E435 uses a voltage-threshold method to estimate charge level. After a cell replacement, the player's internal reference points no longer match the new cell's discharge curve. This causes the percentage display to jump — sometimes skipping from 80% to 20% without warning. Run two or three full charge-to-discharge cycles and the indicator recalibrates to the replacement cell's actual voltage curve.

Playback cutting out before the battery indicator shows empty

The audio amplifier in the NW-E435 draws a brief current spike when driving headphone output at higher volumes. Near the end of a discharge cycle, cell voltage sags under that load and briefly drops below the amplifier's minimum operating threshold. The player cuts audio output as a protective response, even if the battery indicator still reads a few percent remaining. If this happens consistently, the replacement cell is likely at or near end of discharge — connect the charger until the device reports full, then check that resting voltage reads 4.15V to 4.20V.