JBL Tune 225 TWS Charging Case Compatible Battery 3.7V 350mAh

JBL Tune 225 TWS Charging Case — 3.7V Li-Polymer Replacement Battery (GSP571935 02)

This 3.7V, 350mAh Li-Polymer battery replaces the internal cell in the JBL Tune 225 TWS charging case. The case uses this cell to store charge and top up the earbuds between uses. When the original cell degrades, the case stops holding charge — swapping this cell restores that function.

• Tune 225 TWS case fit: This battery matches the GSP571935 02 spec used in the Tune 225 TWS case housing. The 36.90 × 18.80 × 5.80mm footprint, 3.7V nominal voltage, and connector orientation all match the original PCB layout. No modification needed to seat the cell.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the Tune 225 TWS case. The protection circuit triggered correctly at low-voltage cutoff, and the case passed charge to both earbuds without interruption across multiple cycles.
• First charge after replacement: After fitting, charge the case via USB until the LED indicator confirms full charge before placing earbuds inside. The new cell ships at storage voltage — placing earbuds in immediately will draw from a partially charged cell and the case may show a depleted state sooner than expected.

Why the Tune 225 TWS case stops charging earbuds before the indicator shows empty

A degraded Li-Polymer cell loses usable capacity at the margins first — the voltage drops below the threshold needed to push charge into the earbuds' cells before the case indicator reads zero. The case LED reflects a rough state-of-charge estimate, not real-time output voltage. Once the cell cannot sustain the voltage required by the charging circuit, earbud top-ups stop even though the indicator shows partial charge remaining. Replacing the cell brings output voltage back to spec and the full charge-transfer range is restored.

Case LED shows full charge but earbuds cut off after short use

This happens when the replacement cell — or a worn original — is at storage voltage rather than a true full charge. The indicator reads the resting voltage and reports full, but the cell cannot sustain current delivery once the earbuds draw load. Place the case on USB charge for a complete cycle before use. Once the cell reaches 4.2V and the LED confirms full, the earbuds will draw a consistent charge from the case.