About this replacement
Samsung Galaxy Tab S9 FE — 3.86V Li-Polymer Replacement Battery (EB-BX818ABY)
This 3.86V, 9800mAh Li-Polymer battery replaces the original cell in the Samsung Galaxy Tab S9 FE. It fits the SM-X816N, SM-X816, SM-X818A, and related Tab S9 FE variants. Install it when the original battery no longer holds charge, swells, or causes unexpected shutdowns.
- Tab S9 FE platform fit: The SM-X816 series and SM-X818A share the same 3.86V battery bay, connector pinout, and BMS handshake protocol. One replacement cell covers the full Tab S9 FE range without adaptation.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Tab S9 FE unit. The BMS accepted the cell, charge IC communicated correctly, and no protection cutoffs were triggered during normal tablet loads.
- Post-swap fuel gauge reset: After installation, run one full discharge to automatic shutoff, then charge uninterrupted to 100%. This recalibrates the fuel gauge IC against the new cell's actual capacity curve and clears the inaccurate percentage readings that appear immediately after a swap.
Fast charging unavailable after battery swap on the Tab S9 FE
Samsung's adaptive fast charge protocol requires the charge IC to complete at least one accepted full charge cycle before it re-enables higher current delivery to a new cell. Immediately after a swap, the tablet may default to standard 5W charging as a safety measure. Connect the original Samsung charger and allow one full charge cycle from low battery to 100% without interruption. After that cycle, fast charging typically re-enables automatically.
Tab S9 FE shutting down at 15–25% battery remaining
When display brightness is high and Wi-Fi is active simultaneously, combined current draw can pull the cell voltage below the BMS protection threshold faster than the fuel gauge predicts. The fuel gauge was calibrated against the old degraded cell, so its remaining-capacity estimate no longer maps accurately to actual voltage. Run one full discharge cycle — let the tablet power itself off at 0%, then charge uninterrupted to 100%. This resets the calibration and stops premature shutdowns at the 3.5V floor the BMS is protecting against.