About this replacement
JBL Free Truly Charging Case — 3.7V Li-Polymer Replacement Battery (GSP853450 01)
This 3.7V, 1200mAh Li-Polymer battery replaces the internal cell in the JBL Free Truly wireless earbud charging case. The case uses this battery to store charge and deliver power to the earbuds between uses. When the original cell degrades, the case can no longer complete multiple earbud charging cycles before dying.
- JBL Free Truly Charging Case fit: The Free Truly case uses a specific cell footprint — 69.30 x 30.00 x 7.10mm — with a soft Li-Polymer pouch construction. The case BMS reads cell voltage on connection. This replacement matches that voltage profile so the case fuel gauge reports correctly after installation.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge on the case PCB. The BMS accepted the pack without error, and the charge indicator LEDs cycled normally through all four stages.
- First-cycle protocol for the Free Truly case: After fitting this battery, place the case on charge via USB-C before dropping the earbuds in. Let the case reach a full charge on its own first. This lets the case BMS log the new cell capacity before it starts tracking earbud charge delivery.
Case LED showing full charge but earbuds die after one cycle
A freshly installed Li-Polymer cell ships at storage voltage — typically around 3.6V — not a fully charged 4.2V. The case fuel gauge reads the cell state incorrectly at that voltage and can report a false full. The earbuds then draw from a cell that has far less usable capacity than the gauge shows. Charge the case to 4.2V via USB-C before use and the fuel gauge re-calibrates against the actual cell state.
Case charge indicator stuck on first LED despite hours on USB-C
If the LED stays on the first bar after a full charge session, the BMS handshake between the new cell and the case PCB may not have completed on the first connection. Disconnect the USB-C cable, wait 10 seconds, then reconnect. This forces the PCB to re-poll the cell. If the indicator still does not advance, check the battery connector is fully seated — the pouch connector on this case requires firm, even pressure to engage all contacts.