iBasso DX50 Replacement Battery 3.7V 1400mAh Li-ion

iBasso DX50 / DX90 Series — 3.7V Li-ion Replacement Battery

This is a 3.7V, 1400mAh (5.18Wh) Li-ion cell for the iBasso DX50, DX90, and DX90J portable high-resolution audio players. It fits the same battery bay across all three models and runs on the same voltage rail. Install it when the original cell no longer holds a charge through a full listening session.

• DX50, DX90, and DX90J compatibility: All three models share the same 3.7V single-cell architecture, connector pinout, and battery bay dimensions (63.00 × 50.40 × 5.40mm). The BMS on each device communicates with the cell over the same protection circuit layout, so one cell works across the whole line without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a test rig mirroring the DX50 charge IC. The protection circuit tripped correctly at both the high-voltage cutoff and low-voltage floor, and the cell held capacity within spec across multiple cycles.
• Fuel gauge recalibration after swap: After fitting this cell, run one complete discharge down to auto-shutdown, then charge uninterrupted to 100% before normal use. The DX50 and DX90 use a coulomb counter that is still calibrated to the old cell's discharge curve — one full cycle resets that baseline against the new cell.

Why the DX50 and DX90 report wrong battery percentage after a cell swap

The DX50 and DX90 track charge state using a coulomb counter — a fuel gauge IC that accumulates charge and discharge current over time. When you replace the cell, the counter still holds learned data from the old, degraded cell, so the percentage shown on screen no longer matches actual capacity. This mismatch shows up most visibly as the percentage sitting high for too long, then dropping sharply in the final quarter. One full discharge-to-shutdown followed by an uninterrupted charge to 100% forces the IC to relearn the new cell's full-capacity endpoints.

Sudden shutdown at 20–30% on the DX90 after replacement

If the device cuts out while the screen still shows 20–30% remaining, the fuel gauge IC is reading a stale discharge curve, not the new cell's actual voltage floor. Under load — especially with high-gain output or a demanding IEM — cell voltage sags faster than the counter predicts, and the device hits the hardware undervoltage cutoff before the software percentage reaches zero. This is not a faulty cell. Charge the unit fully, then play at normal volume until it shuts down on its own. After that single calibration cycle, the cutoff point and the displayed percentage will align. The target resting voltage after a full charge should read around 4.18–4.20V at the battery terminals.