About this replacement
FitBit One — 3.7V Li-Polymer Replacement Battery (LSSP281324AB)
This is a 3.7V 60mAh Li-Polymer cell for the FitBit One clip-on fitness tracker. It replaces part number LSSP281324AB when the original cell can no longer hold enough charge for normal daily use. The FitBit One is a compact device with tight dimensional tolerances — this cell measures 20.30 x 12.90 x 4.20mm to match the original.
- FitBit One fit: The One uses a dedicated clip housing with a fixed battery bay. The LSSP281324AB footprint is specific to this model — the connector orientation and cell dimensions are not shared with other FitBit clip-on variants.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the One platform. The BMS accepted the new cell without fault flags, and the fuel gauge IC responded correctly once a full charge cycle was completed from near-zero.
- Post-swap charging protocol for the FitBit One: Place the device on its charging cradle immediately after fitting this cell and charge to 100% before use. The fuel gauge IC on the One loses its reference point when the cell is swapped — skipping this step causes the percentage readout to stay at 0% or report inaccurately for days.
Why the FitBit One sleep tracking drains this cell faster than step counting
Sleep tracking on the One keeps the accelerometer active through the night in a continuous logging state, rather than the lower-power polling mode used during daytime step counting. On a 60mAh cell, that sustained draw is proportionally significant. If you enable sleep tracking every night, expect shorter intervals between charges compared to step-only use. Turning off sleep tracking when you are not actively monitoring it is the most direct way to extend time between charges on this platform.
FitBit One showing 0% and not powering on after battery replacement
This is a fuel gauge IC calibration loss, not a faulty cell. When the original battery is removed, the IC loses its charge reference entirely and defaults to 0% or refuses to boot. Place the One on its charging cradle straight after fitting the new cell and leave it until the indicator shows a full charge. Do not attempt to power it on mid-charge to check progress. Once it reaches 100%, the IC re-establishes its reference and the device boots normally.