About this replacement
Samsung M40 Series — 11.1V Li-ion Replacement Battery (SSB-X15LS3)
This is an 11.1V, 4400mAh (48.84Wh) Li-ion replacement battery for the Samsung M40 and M40 Plus notebook range. It fits the M40, M40 Plus HWM 745, M40 Plus WVM 1600, and over 28 additional M40 Plus variants. Physical dimensions are 204.85 x 48.10 x 21.40mm — confirm clearance before ordering if your bay has been modified.
- M40 and M40 Plus compatibility: All M40-series models share the same voltage rail, connector pinout, and BMS handshake protocol. The SSB-X15LS3, SSB-X15LS6, SSB-X15LS9, and their regional variants (C, E, S suffixes) are all electrically identical — suffix differences reflect regional packaging, not cell chemistry or connector type.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an M40 unit. The BMS communicated correctly with the system, charge termination triggered at the expected cutoff voltage, and no thermal flags were raised during the load cycle.
- Post-install discharge cycle: After fitting this battery, run one full discharge until the laptop hibernates, 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 every cell swap.
BIOS reporting poor battery health immediately after fitting a new M40 cell
The Samsung M40 BIOS reads health data stored in the battery's EEPROM. When a new cell arrives, this EEPROM contains factory default values that don't match the actual charge history the BIOS expects to see. The system flags this mismatch as degraded health — it is not a fault with the replacement cell. Run one full discharge-to-hibernate cycle followed by an uninterrupted full charge. After two to three cycles, the BIOS recalibrates and the health warning clears.
M40 shutting down abruptly at 20–30% charge shown on screen
This happens when the cell cannot sustain voltage under the combined load of the CPU and display — the voltage drops faster than the fuel gauge IC predicted, hitting the protection cutoff before the displayed percentage reaches zero. It is a calibration gap between the old cell's discharge curve and the new cell's actual curve, not a defective battery. Force a full discharge to hibernate-cutoff, then charge to 100% without interruption. After two calibration cycles, the fuel gauge IC maps the new cell's curve accurately and the premature shutdowns stop.