About this replacement
Lenovo Yoga 2 Pro Ultrabook — 7.4V Li-Polymer Replacement Battery (L12M4P21)
This is a 7.4V, 7400mAh (54.76Wh) lithium-polymer replacement battery for the Lenovo Yoga 2 Pro Ultrabook. It fits the Yoga 2 Pro 13.3", Yoga 2 Pro-13 59-382893, and Yoga 2 Ultrabook variants. Cross-reference OEM part numbers L12M4P21, 121500156, or 11S121500 before ordering to confirm fit.
- Yoga 2 Pro and Yoga 2 compatibility: These models share the same 7.4V two-cell Li-Polymer configuration, connector pinout, and BMS communication protocol. The battery management system handshake is identical across the Yoga 2 and Yoga 2 Pro 13.3" boards, so one cell fits both platforms without modification.
- Bench tested on actual hardware: We ran this cell on a Yoga 2 Pro motherboard and confirmed the BMS handshake completes correctly — the system recognised the cell, initiated a full charge cycle, and the protection circuit responded to both over-current and over-temperature thresholds as expected.
- Post-install calibration cycle: 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 that typically appears after any cell swap on Yoga 2 Pro hardware.
BIOS reporting poor battery health immediately after fitting a new cell
The Yoga 2 Pro BIOS reads EEPROM data embedded in the battery pack to assess health status. When a new cell is installed, the EEPROM cycle count and capacity history are reset to factory defaults, which the BIOS can misread as a degraded or unknown cell. This is a firmware interpretation issue, not a fault with the replacement battery. Running the full discharge-to-hibernate then uninterrupted charge cycle outlined above allows the BIOS to re-establish its battery learn baseline and clears the health warning.
Yoga 2 Pro shutting down abruptly at 20–30% charge shown on screen
This symptom points to a voltage cliff in a degraded original cell — not the replacement. When the CPU boosts alongside the backlit touchscreen display, instantaneous current draw spikes sharply. A worn cell cannot sustain the voltage rail under that combined load and drops below the BMS cutoff threshold, triggering an immediate shutdown even though the fuel gauge still reads 20–30%. Fitting this replacement cell and completing one full calibration cycle resets the fuel gauge IC against the new cell's actual voltage curve, and the shutdowns stop. Confirm the fix by checking battery voltage in Lenovo Vantage — it should hold above 7.0V under full load.