Asus E502M Replacement Battery 11.4V 4050mAh B31N1427

Asus VivoBook E502MA Series — 11.4V Li-ion Replacement Battery (B31N1427)

This is an 11.4V, 4050mAh (46.17Wh) Li-ion replacement battery for the Asus VivoBook E502M and E502MA series laptops, including the Eee Book E502MA and E502MA-XX0004D. It replaces OEM part numbers B31N1427 and 0B200-01430000. Fits the three-cell battery bay on these 15-inch budget notebooks directly.

• E502M and E502MA platform fit: Both the E502M and E502MA share the same three-cell 11.4V battery bay, identical connector pinout, and the same BMS communication protocol over the SMBus line. One cell fits both variants without modification.
• Bench tested on actual hardware: We ran this cell on an E502MA board and confirmed the BMS handshake completed within one charge cycle. The SMBus negotiation returned correct voltage and temperature data to the EC, and the charge controller accepted full current without flagging a fault condition.
• Post-install discharge cycle on the E502MA: After fitting this cell, run a full discharge to the hibernate cutoff, then charge uninterrupted to 100% without suspending or sleeping the machine. This resets the BIOS battery learn cycle on the E502MA EC and clears the false health warning that appears after every cell swap on this platform.

Why the E502MA reports a low battery Wh rating after a cell swap

The E502MA's embedded controller reads Wh capacity from the battery's EEPROM, not directly from the cells. The EEPROM on a new cell carries factory-rated values that can differ slightly from the outgoing cell's worn figures. Windows will display the new EEPROM value in Device Manager, which often reads lower than expected immediately after installation. After one full calibration cycle — full discharge to hibernate, full charge to 100% — the EC recalculates and logs the corrected design capacity against the new cell chemistry.

E502MA shutting down at 20–30% charge remaining

This happens when the cell voltage drops below the EC's cutoff threshold under combined CPU and display load, even though the fuel gauge still shows charge remaining. The fuel gauge IC was calibrated against the old degraded cell, so its percentage curve no longer matches the new cell's discharge profile. The EC sees the voltage cliff before the gauge catches up, and triggers an emergency shutdown. Run two to three full discharge-to-hibernate and charge-to-100% cycles to let the fuel gauge IC recalibrate against the new cell — after that, shutdown should not occur above 5–8% remaining.