About this replacement
Samsung Galaxy S7 Active / SM-G891A — 3.85V Li-Polymer Replacement Battery (EB-BG891ABA)
This is a 3.85V, 4100mAh Li-Polymer replacement battery for the Samsung Galaxy S7 Active (SM-G891, SM-G891A). It replaces OEM part numbers EB-BG891ABA and EB-EG891ABA. Dimensions are 90.20 × 40.90 × 6.24mm — verify clearance before seating the cell if the adhesive strip on the original pulled the frame.
- SM-G891 and SM-G891A compatibility: Both model variants use the same voltage rail, connector pinout, and BMS handshake. One cell fits both. No adapter or firmware change is needed.
- Bench tested on actual hardware: We cycled this cell on an SM-G891A and logged the BMS communication across charge and discharge. The protection circuit responded correctly to overvoltage and thermal thresholds, and the device accepted USB-PD negotiation without falling back to standard 5V charging after the first full cycle.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. The fuel gauge IC on the S7 Active calibrates its coulomb counter against the new cell's discharge curve. Skipping this step causes the OS to report percentage from the old cell's data — leading to inaccurate readings for several days.
Sudden shutdown at 20–30% on the S7 Active after a cell swap
This is a voltage cliff issue, not a capacity defect. The S7 Active's modem and display draw sharp current spikes — during those spikes, a freshly installed or uncalibrated cell can drop below the BMS cutoff voltage momentarily, even though the fuel gauge shows 20–30% remaining. The phone shuts down to protect the cell. One full discharge-charge cycle without fast charging lets the fuel gauge IC map the new cell's actual voltage curve and tighten the low-voltage estimate. After calibration, the shutdowns stop at a correctly reported 3–5%.
USB-PD fast charge not triggering on the first cycle after replacement
After a cell swap, the S7 Active's charge IC sometimes defaults to standard 5V/1A on the first charge session. This happens because the BMS on the new cell has not yet completed its initial handshake with the phone's charge controller — the controller falls back to the safest available profile. Plug in via a USB-PD charger, let the phone reach 100%, then unplug and replug. On the second session, the charge IC re-negotiates and fast charging resumes at the correct rate.