About this replacement
Samsung Galaxy S24 Ultra — 3.88V Li-Polymer Replacement Battery (EB-BS928ABY)
This is a 3.88V, 4800mAh Li-Polymer replacement battery for the Samsung Galaxy S24 Ultra, including SM-S928J, SM-S928Q, SM-S928D, and related variants. It replaces OEM part EB-BS928ABY and GH82-33387A directly. Swap it when the original cell no longer holds charge or causes erratic percentage readings.
- S928 platform fit: All SM-S928 variants share the same battery bay dimensions, connector pinout, and BMS handshake protocol. This cell meets that spec at 73.70 × 60.80 × 5.70mm and 3.88V nominal, so the board communicates with it without error flags.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on SM-S928 hardware. The BMS accepted the cell on first connection, thermal readings during charge stayed within normal range, and no protection cutoff events triggered under standard load.
- Fuel gauge recalibration on first cycle: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard speed. The fuel gauge IC in the S24 Ultra calibrates its coulomb counter against the new cell's discharge curve — skipping this step causes percentage jumps and false low-battery warnings early on.
Sudden shutdown at 20–30% on the Galaxy S24 Ultra after a cell swap
The S24 Ultra's Snapdragon platform pulls hard current spikes when the modem is active or the display runs at peak brightness. A new cell with an uncalibrated fuel gauge IC can report 25% remaining while actual cell voltage has already dropped near the cutoff threshold. The BMS trips at roughly 3.0V per cell to protect the chemistry, and the phone cuts out without warning. One full standard-rate discharge-charge cycle lets the coulomb counter map the actual voltage curve of the new cell, pushing the trip point back to where the percentage readout is accurate.
USB-PD fast charge not activating on the first cycle after replacement
After a cell swap, the S24 Ultra's charge IC may not negotiate the high-current USB-PD contract on the very first charge. The BMS needs to confirm cell impedance is within safe range before it allows elevated current — on a fresh cell this handshake can take one full standard charge to complete. If fast charge appears missing, plug in with the original Samsung charger, let the device charge to 100% at whatever rate it accepts, then unplug and replug. Fast charging typically resumes from the second cycle once the BMS clears its initialization flag.