About this replacement
Asus B9440UA / B9440FA Series — 15.4V Li-Polymer Replacement Battery (C41N1619)
This is a 15.4V, 3050mAh (46.97Wh) lithium-polymer cell for the Asus VivoBook B9440UA and B9440FA ultrabook line. It replaces OEM part numbers C41N1619 and 0B200-02350100. Fit models include the B9440UA-GV0361R, B9440FA-GV0101R, B9440UA-GV0210T, B9440UA-0271A7500U, and over 70 additional B9440-series variants.
- B9440UA and B9440FA compatibility: Both series run the same 15.4V four-cell Li-Polymer configuration and share an identical connector pinout and BMS handshake protocol — the EEPROM cell data format is consistent across all B9440 SKUs, which is why one battery covers the full range.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a B9440UA unit. The BMS communicated correctly with the BIOS, charge current tapered normally at the top-of-charge plateau, and no fault codes were logged during the session.
- Post-install calibration on B9440 series: After fitting this battery, run the laptop down until it hibernates on its own, then charge it uninterrupted to 100% without using the machine. This resets the BIOS battery learn cycle and clears the inaccurate health warning that almost always appears after a cell swap on this platform.
Why the B9440 BIOS flags a new battery as poor health immediately after swap
The B9440 BIOS reads health status from EEPROM data embedded in the battery's BMS chip. When a replacement cell arrives, the EEPROM counters are at factory defaults — cycle count zero, full charge capacity at rated spec — but the BIOS compares this against the learned profile from the old battery and flags a mismatch as degraded health. This is not a fault with the new cell. One full discharge-to-hibernate followed by an uninterrupted full charge gives the BIOS enough data to overwrite the old learned profile and report health correctly.
B9440 shutting down at 20–30% charge shown on screen
This happens when the fuel gauge IC has not yet calibrated against the new cell's actual chemistry. The IC is still using the discharge curve from the old, degraded battery, so it misjudges the voltage cliff — the point where cell voltage drops sharply under full CPU and display load. The laptop cuts power before the gauge reaches zero because the real cell voltage has already fallen below the BMS minimum threshold. Run two complete discharge-to-hibernate and full-recharge cycles, and the fuel gauge IC will recalibrate to the new cell's curve — the shutdowns stop once it tracks voltage accurately to below 10%.