XDUOO X3 Mark II Replacement Battery 3.7V 1750mAh

XDUOO X3 Mark II — 3.7V Li-Polymer Replacement Battery (YT653071)

This 3.7V, 1750mAh lithium-polymer battery replaces the original YT653071 cell in the XDUOO X3 Mark II portable digital audio player. The X3 Mark II is a dedicated hi-fi DAP, not a smartphone — it runs a single-core media stack with a discrete DAC and amp circuit drawing consistent current throughout playback. Dimensions are 73.00 × 31.50 × 6.60mm; verify these against your existing cell before installing.

• X3 Mark II cell compatibility: The X3 Mark II uses a single flat Li-Polymer pouch cell connected directly to the DAC/amp power rail. There is no mid-series voltage conversion — the cell voltage feeds the amp stage at source, so the replacement cell must match the 3.7V nominal rating exactly to keep the output stage biased correctly.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the X3 Mark II platform. The onboard BMS accepted charge current without tripping, held the 3.7V nominal under load from the DAC and amp circuit, and completed the protection handshake cleanly at both the low-voltage cutoff and full-charge threshold.
• Post-swap initialisation on the X3 Mark II: After fitting a new cell, connect the X3 Mark II to its charger before powering on. Media players with a depleted or freshly installed cell often sit below the BMS wake threshold — the charger delivers trickle current to bring the cell above that threshold before the device will boot.

Battery percentage jumping after a cell swap on the X3 Mark II

The X3 Mark II estimates charge level by reading cell voltage against a fixed lookup table stored in firmware. A new cell has a different voltage-to-capacity curve than the worn cell it replaces, so the indicator reads inaccurate percentages for the first few cycles. The fix is to run two or three full charge-to-discharge cycles without interrupting them mid-way. After that, the voltage curve the firmware sees aligns closely enough with the lookup table to give stable readings. Expect the percentage to settle within ±5% of actual state of charge by the third cycle.

Playback cutting out before the battery indicator reaches empty

The discrete amplifier stage in the X3 Mark II needs a minimum cell voltage — typically around 3.2V — to maintain clean output. As the cell nears the end of its discharge curve, voltage sags faster under the amp's load than the percentage indicator anticipates. The BMS shuts the output stage down to protect the cell before the display shows zero. If this happens frequently on an older cell, the cell has lost capacity and can no longer sustain the amp's draw through the full discharge curve — replacing the cell resolves it.