About this replacement
MSI Modern 14 Series — 11.4V Li-Polymer Replacement Battery (BTY-M49)
This is an 11.4V, 4400mAh (50.16Wh) Li-Polymer replacement battery for the MSI Modern 14 and GS40 Phantom series laptops. It uses OEM part number BTY-M49 and fits a wide range of MSI notebook models including the Modern 14 B4M (MS-14DK) and Modern 14 B4MW (MS-14DK). The cell dimensions are 251.00 x 94.00 x 5.70mm — verify your original before installing.
- Modern 14 and GS40 platform fit: These models share the same BTY-M49 voltage rail and three-cell Li-Polymer configuration. The connector pinout and BMS handshake protocol are identical across the MS-14DK board variants, so no firmware workaround is needed for the swap.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an MS-14DK board. The BMS accepted the cell immediately, charge current ramped correctly from CC to CV phase, and the protection circuit triggered cleanly at the low-voltage cutoff threshold.
- First-cycle calibration after swap: After installing, run one full discharge until the laptop hibernates on its own, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears on the first boot after any cell replacement.
Laptop shutting down at 20–30% remaining after battery swap
This happens because the fuel gauge IC on the MSI board still holds calibration data from the old cell. When the new cell's actual voltage under CPU and display load drops below what the old calibration expected, the board treats it as a critical shutdown threshold — even though charge remains. The fix is a full discharge-to-hibernate cycle followed by an uninterrupted charge to 100%, repeated two to three times. After that, the fuel gauge recalibrates against the new cell's voltage curve and the early shutdowns stop.
BIOS reporting battery health as "poor" or "replace now" on first boot
The BIOS reads health status from EEPROM data written by the old cell's BMS before it was removed. A fresh cell has no cycle history stored yet, so the BIOS flags it as degraded rather than new. This is a data mismatch — not a fault with the replacement cell. Run the battery learn cycle: discharge fully to hibernate cutoff, charge uninterrupted to 100%, and reboot. The BIOS reads the updated EEPROM state and the health warning clears.