About this replacement
Samsung Galaxy M42 — 3.85V Li-Polymer Replacement Battery (EB-BM425ABY)
This is a 3.85V, 4700mAh (18.1Wh) Li-Polymer battery for the Samsung Galaxy M42 smartphone. It replaces part number EB-BM425ABY when the original cell degrades, loses hold time, or fails to charge correctly. The battery restores full operational capacity to the M42's Snapdragon 750G platform, display, and modem stack.
- Galaxy M42 cell fitment: The M42 uses a dedicated battery bay sized for the EB-BM425ABY footprint — 82.70 × 65.22 × 5.10mm. The connector position and BMS handshake are matched to the M42's charge IC, so the device recognises the cell and enables Samsung's adaptive charging protocols without error flags.
- Bench tested on actual hardware: We ran this cell through the M42's charge controller and confirmed full BMS communication, correct voltage ramp from trickle to CC/CV phase, and clean charge termination at 4.35V. No charge IC error codes triggered during our test cycles.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated coulomb counter — preventing early percentage drift.
Sudden shutdown at 20–30% on the replacement cell
This happens because the fuel gauge IC on the M42 is still using the discharge curve of the old, degraded cell. When a fresh cell with a steeper voltage-drop profile hits a load spike — modem handoff, screen-on burst — the actual cell voltage collapses below the shutdown threshold faster than the gauge predicts. The phone cuts off even though reported percentage looks safe. One full discharge-charge cycle without fast charging allows the coulomb counter to recalibrate to the new cell curve. After that cycle, shutdowns at 20–30% stop.
USB-PD fast charge not activating on the first cycle after installation
After a cell swap, the M42's charge IC may default to standard 5V/1A input for the first charge session. This is a BMS safety state — the controller holds back high-current charging until it completes one handshake cycle with the new cell's protection circuit. Plug in with the original Samsung charger and leave it until the phone reaches 100% without interruption. On the next charge session, fast charge resumes at the correct input rate and the charging icon updates accordingly.