About this replacement
Globalstar GH625XT — 3.7V Li-Polymer Replacement Battery (H553438)
This is a 3.7V, 750mAh lithium-polymer cell for the Globalstar GH625XT smartwatch. It replaces OEM part number H553438 and restores power to the watch's timekeeping, fitness tracking, and GPS functions. Capacity is sourced from product data at 2.78Wh — do not substitute a lower-capacity cell.
- GH625XT platform fit: The GH625XT uses a fixed 3.7V single-cell Li-Po architecture with a dedicated fuel gauge IC. This cell matches the OEM voltage rail and physical footprint (37.50 × 32.40 × 5.00mm), so the BMS accepts the swap without a firmware flag.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the GH625XT platform. The BMS accepted the cell without error, and the fuel gauge reported state-of-charge correctly after a full calibration cycle from near-zero.
- Fuel gauge calibration after swap: Place the watch on its charger immediately after fitting this cell and charge it to 100% before use. The GH625XT's fuel gauge IC loses its reference point when the original cell is removed — it cannot calibrate correctly unless it sees a full charge cycle starting from near-zero on the new cell.
Why the GH625XT shows 0% immediately after a battery swap
The GH625XT uses a coulomb-counting fuel gauge IC that tracks charge by measuring current flow over time. When you remove the original cell, that accumulated reference data is lost entirely. The IC has no baseline for the new cell, so it defaults to 0% or an arbitrary low reading. Connecting the watch to its charger and completing a full charge to 100% resets the gauge and restores accurate percentage reporting.
Battery draining in one day instead of several after replacement
Continuous heart rate monitoring and GPS logging are the two largest current draws on the GH625XT platform. If both are active simultaneously, the 750mAh cell will deplete significantly faster than when only timekeeping is running. Check your activity tracking settings — always-on HR monitoring alone can triple the daily draw compared to on-demand mode. Switch HR monitoring to manual or reduce GPS fix frequency to recover multi-day use.