XDUOO X3 Replacement Battery YT613773 3.7V 1900mAh

XDUOO X3 — 3.7V Li-Polymer Replacement Battery (YT613773)

This is a 3.7V, 1900mAh Li-Polymer cell for the XDUOO X3 portable digital audio player. It replaces part number YT613773 when the original cell has degraded or failed. Capacity is rated at 7.03Wh and matches the stock cell dimensions at 73.60 × 36.70 × 6.10mm.

• X3 platform fit: The X3 uses a slim Li-Polymer pouch cell on a 3.7V rail. This cell shares the same footprint and connector pinout as the factory unit, so the BMS on the X3 mainboard reads charge state correctly without any firmware conflict.
• Bench tested on actual hardware: We ran this cell through charge cycles on the X3 mainboard. The BMS accepted the cell without triggering a protection cutoff, and the charge controller stepped through CC/CV phases cleanly to 4.2V.
• Post-install charge cycle on the X3: Media players commonly enter a deep-discharge protection state after extended storage or a flat cell swap. Connect the X3 to a charger immediately after fitting this cell and leave it for at least 30 minutes before attempting to power on — this lets the charger trickle enough current to bring the cell above the BMS wake threshold.

Battery percentage jumping erratically after cell swap on the X3

The X3 estimates charge state by reading cell voltage against a fixed lookup table stored in firmware. A new cell has a slightly different voltage-to-capacity curve than an aged one, so the indicator can jump between readings — especially between 40% and 80% — for the first few charge cycles. This is a calibration drift, not a fault with the cell. Run two or three full charge and discharge cycles through the X3 and the indicator will stabilise as the firmware maps the new cell's curve.

Playback cutting out before the X3 shows the battery as empty

The X3's audio amplifier stage draws a higher current spike during playback than the device draws at idle. As the cell approaches the bottom of its discharge curve, voltage sags under that load even though the resting voltage still reads as non-empty. The BMS interprets the sag as an undervoltage condition and cuts output to protect the cell. If this happens consistently at a certain percentage, force a full charge to 4.2V and avoid running the player below 10% charge until the cell has completed a few full cycles.