JBL Free Replacement Battery GSP853450 3.7V 1200mAh

JBL Free / Free X Truly Wireless — 3.7V Li-Polymer Replacement Battery (GSP853450)

This 3.7V, 1200mAh lithium-polymer cell replaces the GSP853450 battery inside JBL Free and Free X Truly Wireless earbuds. It fits the left or right earbud housing and restores playback capacity lost to cell degradation. Dimensions are 38.00 × 36.50 × 8.00mm — measure your existing cell before ordering if you are unsure which earbud is failing.

• Free and Free X compatibility: Both models share the same earbud housing geometry, 3.7V power rail, and GSP853450 footprint. The BMS logic inside each earbud accepts the replacement cell without firmware intervention.
• Bench tested on actual hardware: We cycled the cell through charge and discharge on a Free earbud. The onboard BMS accepted the new cell, held cutoff at 4.2V charge ceiling, and triggered low-voltage protection at 3.0V with no anomalies.
• First-charge protocol for JBL Free earbuds: After fitting the new cell, place the earbud in the charging case and leave it for a complete charge cycle before pairing. The earbud's fuel gauge resets its capacity estimate during this first session — skipping it causes the battery indicator to misread remaining charge.

Why JBL Free earbuds cut out mid-audio after a battery swap

The Free earbud runs Bluetooth radio, audio decoding, and touch sensor logic from a single 3.7V cell. Under combined load, a cell sitting below 3.6V can sag just enough to trigger the BMS undervoltage cutoff — even if the case indicator shows charge remaining. This is most common when the replacement cell ships at storage voltage around 3.7–3.8V and has not yet been fully cycled. A complete charge to 4.2V before first use stabilises the voltage floor and eliminates most cutout events.

Charging case shows full but earbud dies quickly after replacement

The charging case reads the earbud's reported state-of-charge, not the raw cell voltage — so a new cell at storage voltage can report "full" before it has completed a real cycle. The fuel gauge inside the earbud recalibrates over the first three to five full charge-discharge cycles. Until then, actual usable capacity will read lower than the cell's rated 1200mAh. Run three full cycles — charge to 4.2V, use until the earbud auto-powers off — and the indicator will align with real cell state.