Asus B31N1345 Transformer Book Flip TP500LA Replacement Battery 11.4V 4200mAh

Asus Transformer Book Flip TP500LA/LB/LN Series — 11.4V Li-Polymer Replacement Battery (B31N1345)

This is an 11.4V 4200mAh (47.88Wh) Li-Polymer battery for the Asus Transformer Book Flip TP500LA, TP500LB, and TP500LN. It fits the convertible touchscreen models where the original B31N1345 cell has degraded. Voltage and connector match the OEM spec exactly.

• TP500 series compatibility: The TP500LA, TP500LB, and TP500LN all share the same 11.4V three-cell battery rail, connector pinout, and BMS handshake protocol — that is why a single part number covers the full lineup. The battery communicates charge state over the same SMBus line across every variant.
• Bench tested on actual hardware: We ran this cell on a TP500LN unit and monitored BMS communication through a full charge and load cycle. The protection circuit responded correctly to cell voltage limits, and the SMBus reported accurate state-of-charge data to the OS throughout.
• Post-install calibration on the TP500: After fitting this battery, run the laptop down to automatic hibernate on battery power alone — no sleep, no plug-in. Then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell and clears the inaccurate health warning that appears in MyASUS or HWiNFO after a cell swap.

Why the TP500LA shuts down at 20–30% shown after a battery swap

The TP500LA runs a combined CPU and display load that can pull the cell voltage down sharply under stress. If the fuel gauge IC has not been calibrated to the new cell's discharge curve, it misreads the remaining charge and triggers a hard shutdown well above actual empty. The BIOS uses the last learned curve from the old cell until a full learn cycle is completed. Running one full discharge-to-hibernate followed by an uninterrupted charge resets this and aligns the gauge to the new cell.

BIOS reporting B31N1345 replacement as poor health or unknown immediately after install

The EEPROM data embedded in the old cell — cycle count, health percentage, rated Wh — does not transfer to a new battery. The BIOS reads the new cell's EEPROM as a blank or mismatched record and flags it as poor health or unknown, even though the cell is new. This is not a fault with the replacement; it is the BIOS comparing the new EEPROM against its stored baseline for the original cell. Complete one full discharge-to-hibernate then a full uninterrupted charge, and the BIOS will write a fresh baseline — the health warning clears after that cycle.