California Access M158N Laptop Compatible Battery 11.1V 4400mAh

California Access M158N — 11.1V Li-ion Replacement Battery

This is an 11.1V, 4400mAh (48.84Wh) Li-ion battery for the California Access M158N notebook. It replaces the original cell pack when the factory battery no longer holds a usable charge. The connector and cell configuration match the M158N battery bay directly.

• M158N platform fit: The M158N uses an 11.1V three-cell series configuration with a specific connector pinout and BMS handshake. This replacement matches that voltage rail and pin layout so the notebook's charge controller recognises the pack on first boot.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on the bench. The BMS held the correct cutoff voltages at both ends — no premature low-voltage shutdown, no overcharge condition detected across the full cycle.
• First-cycle calibration on the M158N: After fitting, run the laptop on battery from 100% down to hibernate cutoff, then charge uninterrupted back to 100%. This gives the BIOS fuel gauge IC a full reference cycle against the new cell chemistry and clears the inaccurate health warning that appears after every cell swap.

BIOS reporting battery health as poor after fitting the M158N replacement

The M158N BIOS reads health data from the battery's EEPROM, which stores cycle count and rated capacity from the previous cell. When a new pack is installed, that EEPROM data does not automatically reset, so the BIOS displays the old cell's degraded health figure. This is a data mismatch, not a fault with the new battery. Run one complete discharge-to-hibernate then a full uninterrupted charge. After that cycle, the BIOS fuel gauge IC recalibrates against the new cell and the health warning clears.

M158N shutting down at 20–30% charge shown on screen

This happens when the cell voltage drops below the BMS cutoff threshold under full load — CPU plus display drawing peak current — even though the OS fuel gauge still shows charge remaining. The fuel gauge IC estimated a safe floor based on old calibration data, but the new cell's actual voltage cliff sits higher until it completes calibration cycles. The fix is to run two to three full discharge-and-charge cycles without interruption. After calibration, the OS percentage and the real cell voltage align, and the premature shutdown stops. Target resting voltage after a full charge should read approximately 12.6V at the pack terminals.