MSI PS42 8RC-027tw Compatible Battery 15.2V 3250mAh BTY-M48

MSI PS42 8RC/8RB/8M Series — 15.2V Li-Polymer Replacement Battery (BTY-M48)

This is a 15.2V, 3250mAh (49.4Wh) Li-Polymer replacement battery for the MSI PS42 ultrabook line, including the PS42 8RC-027tw, PS42 8RB, PS42 8M, and PS42 Modern 8RC among others. It replaces OEM part BTY-M48 and alternate reference 4ICP5/41/119. The cell matches the original voltage rail and connector configuration for this slim chassis.

• PS42 8RC/8RB/8M compatibility: These PS42 variants share the same 15.2V four-cell Li-Polymer architecture, identical BMS handshake protocol, and the same physical connector — which is why one SKU covers the full range. Swapping between sub-models on this platform does not require a different battery.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the PS42 platform. The BMS negotiated correctly with the EC, charge termination triggered at 100% without overrun, and cell voltage held steady across the discharge curve with no unexpected cutoff.
• Post-install calibration on the PS42: After fitting this battery, run the laptop down to hibernate-cutoff under normal use, then charge uninterrupted to 100% without interruption. This resets the BIOS battery learn cycle and clears the inaccurate health warning the embedded controller throws after every cell swap.

Why the PS42 BIOS reports poor battery health immediately after replacement

The PS42's embedded controller reads health data from EEPROM registers on the battery's protection circuit. When a new cell arrives, those registers don't yet match the EC's learned parameters from the old pack, so the system flags the battery as degraded before it's ever been used. This is not a fault with the replacement cell — it's a mismatch between stored EEPROM data and the new cell's profile. One full discharge-to-hibernate followed by an uninterrupted charge to 100% lets the EC rewrite its learn-cycle data against the new cell. After that cycle, the health indicator should return to normal.

PS42 shutting down abruptly at 20–30% charge shown

This happens when the fuel gauge IC hasn't yet calibrated against the new cell's actual voltage curve. The gauge miscalculates remaining capacity, and when real cell voltage drops under combined CPU and display load, the EC hits its low-voltage cutoff before the displayed percentage reaches zero. The fix is calibration: two to three full discharge-to-hibernate and full-charge cycles align the fuel gauge IC to the new cell's actual chemistry. After those cycles, the displayed percentage and the real voltage cliff will track accurately — the shutdown-at-30% behaviour stops.