Samsung Galaxy A40 EB-BA405ABE Replacement Battery 3.85V 3000mAh

Samsung Galaxy A40 — 3.85V Li-Polymer Replacement Battery (EB-BA405ABE)

This is a 3.85V, 3000mAh Li-Polymer battery for the Samsung Galaxy A40 smartphone. It fits the SM-A405FM/DS, SM-A405FN/DS, and related A40 2019 variants. It replaces OEM part numbers EB-BA405ABE and GH82-19582A directly.

• A40 series compatibility: All SM-A405 variants share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The 3.85V nominal rail matches what the Exynos 7904 power management IC expects — swapping in a different voltage cell would trip the PMIC's overvoltage protection.
• Bench tested on actual hardware: We ran this cell on an SM-A405FN/DS unit and confirmed the BMS completed charge termination correctly at 4.35V. The fuel gauge IC accepted the new cell and began coulomb counting without error flags on the first full cycle.
• First-cycle fast charge tip: After installation, disable fast charging in Settings and run one full discharge-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell — skipping this step causes erratic percentage readings in the first week.

Sudden shutdown at 20–30% on the Galaxy A40 after a cell swap

This is a voltage cliff, not a calibration error. A new cell with a slightly different discharge curve can hit a voltage floor that the PMIC reads as critical shutdown — even though the coulomb counter still shows capacity remaining. The Exynos 7904's PMIC cuts power when the cell drops below approximately 3.4V under modem or display load, and a fresh cell under peak current draw can sag to that point faster than the fuel gauge predicts. Run two complete discharge cycles without fast charging to let the coulomb counter recalibrate its end-of-discharge voltage model against the actual cell behavior.

USB-PD fast charge not activating on the first cycle after replacement

On the first charge cycle after a cell swap, the Galaxy A40's charge IC may not negotiate the 15W fast charge protocol because the BMS on the new cell has not yet confirmed a valid cell state to the PMIC. The charger falls back to standard 5V/1A as a safety measure. This typically resolves after one complete charge cycle — plug in the original Samsung charger, allow a full charge to 100% at standard rate, then disconnect and reconnect to trigger fast charge renegotiation. If it still does not activate, check that the USB-C port is clean and the adapter output is 9V/1.67A or higher.