Samsung Galaxy Watch Active2 40mm Replacement Battery EB-BR830ABY 3.85V

Samsung Galaxy Watch Active2 40mm — 3.85V Li-Polymer Replacement Battery (EB-BR830ABY)

This 3.85V, 220mAh Li-Polymer cell replaces the original battery in the Samsung Galaxy Watch Active2 40mm (SM-R830, SM-R835). It restores power to the display, processor, heart rate sensor, and wireless radio. Capacity matches the OEM specification — no capacity inflation.

• SM-R830 and SM-R835 fitment: Both the Wi-Fi-only SM-R830 and the LTE SM-R835 use the same 22.00 × 20.60 × 4.90mm cell with the same connector and BMS handshake. The LTE variant draws more current from the modem rail, but the cell spec is identical across both SKUs.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the SM-R830 platform. The BMS accepted the cell without fault flags, fuel gauge initialised correctly after a full charge cycle, and the watch reported battery percentage normally.
• Post-swap charge cycle on the Active2: After fitting this cell, place the watch on its magnetic charger immediately and charge to 100% before first use. The fuel gauge IC on the Active2 loses its reference point when the original cell is removed. Without a full charge cycle from near-zero, the percentage readout will be inaccurate for the first several days.

Why the Active2 reports 0% and shuts down immediately after a battery swap

The Active2 uses a coulomb-counting fuel gauge IC that tracks charge by measuring current flow over time. When the cell is physically removed, that count resets to an undefined state — the IC has no reference for where the new cell sits on its charge curve. The watch reads this as 0% and triggers a low-battery shutdown before the display even fully loads. This is not a fault with the replacement cell. Placing the watch on the charger immediately after reassembly and completing a full charge to 100% resets the fuel gauge to a known anchor point.

Active2 draining to empty within a single day after swap

A new cell on a fresh impedance profile draws differently from the wear-conditioned original, and the Active2's power manager needs one to two charge cycles to recalibrate its draw estimates. Always-on display mode combined with continuous heart rate monitoring pulls the highest sustained current this 220mAh cell handles — both features active simultaneously account for the steepest drain curves we recorded on the bench. If single-day drain continues past three full charge cycles, check whether background app refresh or always-on display was re-enabled during the Tizen OS restart that follows a power interruption. Disable always-on display in Watch Settings → Display and retest.