About this replacement
Sony NW-A1000 / NW-A1200 Series — 3.7V Li-ion Replacement Battery (CT019)
This 3.7V 450mAh Li-ion battery replaces the original CT019 (also listed as 1-157-607-11) in Sony's Network Walkman NW-A1000, NW-A1200, NW-A1200s, and NW-A1200v. It restores full power capacity to players that no longer hold charge after repeated cycle wear on the original cell. Capacity matches the stock spec at 450mAh / 1.67Wh.
- NW-A1000 and NW-A1200 compatibility: These four models share the same PCB layout, connector pin-out, and BMS voltage thresholds, which is why Sony used a single cell part number — CT019 — across the entire sub-series. The cell slots into the same physical housing without modification.
- Bench tested on actual hardware: We cycled this cell on NW-A1000 and NW-A1200 units and confirmed the BMS accepted charge from the dock connector without triggering a protection-trip fault. Charge acceptance, cutoff at full cell voltage, and low-voltage cutoff all matched expected behaviour for a 3.7V Li-ion single cell.
- First charge after cell swap: After fitting this battery, connect the player to its charger before powering it on. A freshly installed cell at partial charge can read below the player's minimum startup voltage. Letting the charger deliver a trickle for 15–20 minutes brings the cell above the BMS power-on threshold and prevents a false dead-device reading.
Why the NW-A1000 shuts down before the battery indicator reaches empty
The NW-A1000's audio amplifier draws a current spike when driving headphone output at higher volumes. Near the end of a discharge cycle, cell voltage sags under that load and drops below the BMS cutoff threshold — even if the on-screen gauge still shows one or two bars. The device shuts off to protect the cell, not because the indicator is accurate. After a full charge cycle on the new cell, the voltage-to-percentage mapping recalibrates and the gauge becomes more consistent. If early shutdowns continue, run two full charge-to-discharge cycles to let the indicator settle.
Battery percentage jumping around erratically after fitting the replacement cell
The NW-A1000 estimates charge level by reading cell voltage against a fixed lookup table stored in firmware. A new cell has a slightly different open-circuit voltage curve than an aged original, so the player's percentage estimate can jump — often 10–20% in either direction — during the first few charge cycles. This is not a fault with the cell or the player. Run two or three full charge and discharge cycles without interrupting them mid-way. By the third cycle the firmware's voltage readings stabilise and the display tracks actual capacity accurately.