FitBit Versa 3 Compatible Battery 3.85V 260mAh LSS352325P

FitBit Versa 3 — 3.85V Li-Polymer Replacement Battery (LSS352325P)

This 3.85V, 260mAh lithium-polymer cell replaces the original LSS352325P battery in the FitBit Versa 3 smartwatch. It restores power to all core functions — fitness tracking, heart rate monitoring, sleep tracking, and notifications. Dimensions are 27.40 × 22.80 × 3.30mm, matching the original cell footprint inside the Versa 3 chassis.

• Versa 3 platform fit: The Versa 3 uses a compact flex connector with a specific pin-out tied to the fuel gauge IC on the mainboard. This cell matches that connector and voltage curve so the BMS can read state-of-charge correctly after the swap.
• Bench tested on actual hardware: We ran this cell on the Versa 3 mainboard and confirmed the BMS accepted the new cell without fault flags. The fuel gauge re-initialised cleanly once the watch completed a full charge cycle from near-zero.
• Post-swap charge cycle on the Versa 3: Place the watch on its magnetic charger immediately after fitting this cell and charge it to 100% before first use. The Versa 3 fuel gauge IC loses its reference point when the old cell is removed — it cannot calibrate state-of-charge without one full charge cycle starting from near-zero.

Why the Versa 3 shows 0% immediately after a battery swap

The Versa 3 uses a coulomb-counting fuel gauge IC that tracks charge by measuring current in and out of the cell over time. When you disconnect the old battery, the IC loses its reference entirely — it has no baseline for the new cell. The watch will display 0% or refuse to boot until it sees a full charge cycle. Put the watch straight on the charger after the swap and let it reach 100% before powering it on.

New battery draining to empty within a single day on the Versa 3

The most common cause is continuous heart rate monitoring running alongside an always-on display — both active at once push draw well beyond what this 260mAh cell is rated to sustain over a full day. Check the display settings and confirm always-on mode is off if it was not intentionally enabled after the swap. Continuous GPS sessions compound this further; the Versa 3 GPS radio alone pulls enough current to deplete the cell in a fraction of a normal use day. Disable continuous HR polling and always-on display, then check drain again — resting draw should keep the watch running across multiple days.