About this replacement
Samsung M40 Plus / X50 Series — 11.1V Li-ion Replacement Battery (SSB-X15LS3)
This 11.1V, 6600mAh Li-ion battery replaces the original cell in the Samsung M40 Plus, NX30, SX15-C16B, X50 WVM 2000, and related notebook models. It slots into the same bay and connects via the same multi-pin connector as the factory pack. Capacity figure is 6600mAh / 73.26Wh — use that number when comparing against your current pack rating.
- M40 Plus and X50 platform fit: These models share the same 11.1V three-cell Li-ion architecture and identical BMS connector pinout. The SSB-X15LS3 part number covers the full OEM cross-reference list, including SSB-X15LS6, SSB-X15LS9, and their regional variants.
- Bench tested on actual hardware: We cycled this pack through charge, full discharge to BMS cutoff, and a second full charge on an M40 Plus unit. The BMS handshake completed cleanly, charge acceptance was normal, and the pack held stable voltage through the discharge curve without unexpected cutoffs.
- Post-install discharge cycle on the M40 Plus: After fitting this battery, run one full discharge to hibernate-cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap on this platform.
BIOS reporting poor battery health immediately after fitting a new cell
The Samsung M40 Plus BIOS reads health data stored in the battery's EEPROM, not from live cell measurements. When a new pack is installed, that EEPROM hasn't yet been written with cycle data matching the new chemistry, so the BIOS flags it as degraded. Running one complete charge-discharge-recharge cycle forces the fuel gauge IC to recalibrate and write fresh data to the EEPROM. After two or three full cycles, the health reading in both BIOS and Windows normalises. No firmware update or driver change is needed — the calibration cycle does the work.
Laptop shuts down abruptly while the OS still shows 20–30% charge
This is a voltage cliff issue, not a capacity fault. Under combined CPU and display load, the cell voltage drops faster than the fuel gauge IC can track, and the BMS triggers a hard cutoff before the displayed percentage reaches zero. It happens most often on the M40 Plus when running a CPU-intensive task on battery with full brightness. The fix is the same learn cycle — discharge fully to hibernate, recharge to 100% without interruption. Once the fuel gauge IC has mapped the real discharge curve of the new cell, the shutdown threshold and the displayed percentage will align.