About this replacement
Dell XPS 14z — 14.8V Li-Polymer Replacement Battery (V79Y0)
This is a 14.8V, 3900mAh (57.72Wh) Li-Polymer replacement battery for the Dell XPS 14z ultrabook. It fits the XPS 14Z-L412X, XPS 14Z-L412Z, and the broader XPS 14Z Ultrabook line. OEM part numbers V79Y0, YMYF6, and 0YMYF6 all cross-reference to this cell.
- XPS 14z series fit: The L412X and L412Z share the same 14.8V four-cell configuration, connector pinout, and BMS handshake protocol. A single cell revision covers both chassis variants without modification.
- Bench tested on actual hardware: We ran this cell through charge, discharge, and load cycles on an XPS 14z unit. The BMS communicated correctly with the EC, reported accurate state-of-charge to the OS, and held voltage within expected range under CPU and display load.
- Post-install calibration on the XPS 14z: After fitting this cell, run one full discharge to hibernate cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning the EC flags after every cell swap.
BIOS reporting poor battery health immediately after replacement
The Dell EC reads EEPROM data embedded in the original cell's BMS and stores it as a baseline. When a new cell arrives, the EC compares the new cell's reported cycle count and charge history against its stored profile — they don't match, so it flags poor health. This is not a fault with the replacement cell. Running the full discharge-to-hibernate then uninterrupted charge cycle forces the EC to re-learn from the new cell's actual data. After one or two complete cycles, the health indicator normalises.
XPS 14z shutting down abruptly at 20–30% charge shown
The fuel gauge IC on the XPS 14z estimates remaining capacity using the old cell's voltage curve. When a new cell is installed, the IC's stored curve no longer matches the actual cell chemistry, so it misreads voltage sag under combined CPU and display load as a critical low. The laptop cuts power before the gauge reaches zero. The fix is calibration: discharge fully until the system hibernates on its own, then charge to 100% without interruption. Repeat this two to three times. After calibration, the gauge tracks the new cell accurately and shutdowns at false lows stop.