FitBit Versa 4 Replacement Battery LSS282024P 3.87V 160mAh

FitBit Versa 4 — 3.87V Li-Polymer Replacement Battery (LSS282024P)

This is a 3.87V, 160mAh lithium-polymer cell that fits the FitBit Versa 4 smartwatch. It replaces part number LSS282024P when the original cell has degraded through repeated charge cycles. The battery measures 24.20 × 20.00 × 2.60mm and connects to the Versa 4's flex PCB via the original ribbon connector.

• Versa 4 cell fitment: The Versa 4 uses a compact Li-Polymer pouch cell at 3.87V nominal — a slightly elevated nominal versus standard 3.7V cells. The BMS on this platform expects that voltage profile. Substituting a mismatched cell voltage causes the fuel gauge IC to report incorrect state-of-charge from the first cycle.
• Bench tested on actual hardware: We cycled this cell through the Versa 4's charge controller and confirmed the BMS accepted the charge profile without triggering an over-voltage cutoff. The fuel gauge re-initialised correctly after a full charge-from-near-zero sequence post-swap.
• Post-swap charge requirement: After fitting this cell, place the Versa 4 on its magnetic charger immediately and charge to 100% before using the watch. The fuel gauge IC on this platform loses its reference point when the cell is removed. Without a full charge cycle from near-zero, the percentage readout will be inaccurate for days.

Why the Versa 4 fuel gauge shows wrong percentages after a cell swap

The Versa 4 uses a coulomb-counting fuel gauge IC that tracks charge in and out relative to a stored full-charge reference. Removing the battery clears that reference from volatile memory. When a new cell is fitted, the IC has no baseline, so it estimates state-of-charge from open-circuit voltage alone — which is unreliable mid-cycle. Running a complete charge to 100% from a low state lets the IC set a new full-charge reference and restore accurate readings within one or two cycles.

Versa 4 not pairing to phone after battery replacement

Removing the battery terminates the active BLE session between the Versa 4 and the paired phone. The watch does not automatically re-establish that bond on power-up — the phone's Bluetooth stack still holds the old session key, and the two devices talk past each other. On the phone, go to Bluetooth settings, forget the Versa 4 device entry, then re-pair through the Fitbit app as if setting up for the first time. The watch itself needs no reset; removing the stale bond on the phone side is enough.