Sony NWZ-A720 Replacement Battery 3.7V 650mAh

Sony NWZ-A720 / NWZ-A728 Series — 3.7V Li-Polymer Replacement Battery (1-756-702-11)

This 3.7V, 650mAh Li-Polymer battery replaces the original cell in the Sony NWZ-A720, NWZ-A728, NWZ-A726, and NWZ-820 Walkman media players. It matches OEM part numbers 1-756-702-11, LIS1374HNPA, and related variants. If your player refuses to hold a charge or dies mid-session, this is the direct replacement cell.

• NWZ-A720 / A726 / A728 / NWZ-820 platform fit: These models share the same compact Li-Polymer cell format, connector pinout, and BMS voltage thresholds. One cell covers the whole series without any wiring or connector modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the NWZ-A728 platform. The BMS accepted full charge current without fault, and the protection circuit triggered correctly at the low-voltage cutoff point.
• Post-swap charge protocol for Walkman players: After fitting a new cell, connect the player to its charger before attempting to power it on. NWZ-series players can enter a deep-discharge protection state during storage or transit, and the firmware requires a short trickle-charge phase before it will accept normal charge current or boot.

Battery percentage jumping after cell swap on NWZ-A series players

After replacing the cell, the NWZ-A720 and related models may display erratic or incorrect battery percentage readings for the first several charge cycles. The firmware's fuel gauge is calibrated to the voltage curve of the original aged cell, not a fresh one. The indicator recalibrates by comparing actual resting voltage against its stored thresholds over repeated cycles. Run two or three full charge and discharge cycles to let the gauge settle.

Playback cutting out before the battery indicator reaches empty

As a Li-Polymer cell approaches the end of its discharge curve, terminal voltage drops sharply under the load of the audio amplifier circuit. The NWZ-A720's amplifier requires a stable voltage floor to sustain output — when the cell can no longer hold that floor, the player shuts down even if the gauge still shows remaining charge. This is amplifier voltage sag, not a faulty cell. If it happens consistently with a fresh replacement battery, check that the cell connector is fully seated, as a loose contact increases resistance and accelerates the voltage drop.