Edifier STAX Spirit S3 Compatible Battery 3.7V 1500mAh

Edifier STAX Spirit S3 — 3.7V Li-Polymer Replacement Battery

This is a 3.7V, 1500mAh Li-Polymer cell built to replace the original battery in the Edifier STAX Spirit S3 wireless headphones. The Spirit S3 runs a planar magnetic driver alongside active Bluetooth and ANC circuitry — that combined draw puts more strain on the cell than a standard earbud. When the original cell degrades, this replacement restores full function without replacing the entire headset.

• STAX Spirit S3 fit: The Spirit S3 uses a slim 50.70 × 34.00 × 8.00mm Li-Polymer pouch cell. The connector pinout and BMS communication lines match the original, so the headset's battery reporting and charge management work as expected after the swap.
• Bench tested on actual hardware: We cycled this cell through the Spirit S3's charge circuit and confirmed the BMS accepted the new pack without throwing a fault. Charge termination at 4.2V cut in correctly, and protection circuitry responded normally to low-voltage conditions.
• First-cycle charging on the Spirit S3: After fitting this cell, run a complete charge from near-flat to full before extended use. The Spirit S3's onboard fuel gauge recalibrates its capacity estimate during that first full cycle — skipping it causes the headset to report incorrect charge levels for several sessions.

Why the Spirit S3 drains faster than expected in the first few cycles

A fresh Li-Polymer cell ships at storage voltage — typically around 3.8V — not at full formation charge. The Spirit S3's power management reads available capacity from the cell's state of charge history, and a new cell has none. Over the first three to five full charge-discharge cycles, the cell's internal resistance settles and deliverable capacity increases noticeably. Do not judge this battery's performance on cycle one.

Headset cuts out mid-listening session after battery replacement

The Spirit S3 runs a planar driver, active noise cancellation, and Bluetooth simultaneously — peak draw spikes sharply when all three are active. If the replacement cell has not completed its first full charge cycle, voltage can sag under that combined load and trigger the BMS undervoltage cutoff before the displayed charge level suggests it should. Charge the headset fully, then allow two or three complete cycles before using all features together at high volume. If cutouts continue after that, check that cell voltage at rest reads at least 3.7V with a multimeter at the connector.