About this replacement
JBL UA SPORT / UAONEARBTBK — 3.7V Li-Polymer Replacement Battery (GSP072035)
This is a 3.7V, 450mAh Li-Polymer cell for the JBL UA SPORT and UAONEARBTBK wireless headsets. It fits inside the ear cup and powers audio playback, calls, and voice assistant functions. Order this when the original cell no longer holds a charge or the headset dies well before rated use.
- UA SPORT and UAONEARBTBK compatibility: Both models use the same GSP072035 cell on a shared 3.7V power rail with identical connector and BMS handshake requirements — swapping the cell is a direct match at the board level.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the UA SPORT platform. The BMS accepted the new pack without fault codes, and voltage held steady under combined DECT radio and audio draw.
- First charge in base station: Seat the headset in the base station and let it run a full charge cycle before making a call. The base needs to log the new cell to report an accurate charge level — skipping this leaves the indicator unreliable for the first few uses.
Why the UA SPORT cuts out mid-call on a new battery
The UA SPORT runs two simultaneous loads — the DECT radio and the audio driver — from a single small cell. On a cell that has not completed its first full charge cycle, the BMS can read voltage as insufficient under that combined draw and trigger a protective cutoff. This is not a faulty battery. Run the headset through two or three complete charge-and-discharge cycles from the base station and the cutouts stop. Voltage stabilises above the BMS trip threshold once the cell is properly conditioned.
Base station shows full charge but headset shuts off after a few minutes
A replacement cell shipped at storage voltage — typically around 3.6V — can register as "full" to the base station before the cell has actually been topped up. The BMS accepts the dock signal but the usable capacity is not there yet. Place the headset in the base, leave it for a complete uninterrupted charge cycle, then check again. After that first full cycle the base and the cell are synchronised and the headset will run to its rated capacity.