About this replacement
Lenovo ThinkPad T430u — 11.1V Li-Polymer Replacement Battery (L11N3P51)
This is an 11.1V, 4250mAh Li-Polymer battery for the Lenovo ThinkPad T430u ultrabook and its sub-variants including the 3351A64, 33512AC, and 33511L0. It replaces OEM part numbers L11N3P51, L11S3P51, 45N1088, 45N1089, 45N1090, and 45N1091 among others. The T430u is a slim 2012-era business laptop, and this cell matches the original voltage rail and connector spec exactly.
- T430u series fit: All listed sub-models share the same 11.1V three-cell architecture, connector pinout, and BMS handshake protocol. The T430u's power board expects a specific SMBus communication sequence on startup — this cell satisfies that handshake without triggering an unknown-battery flag.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a T430u unit, confirming the BMS accepted the cell, charge current ramped correctly through CC/CV stages, and the protection circuit tripped at the expected low-voltage cutoff without a hard shutdown event.
- Post-install learn cycle on the T430u: After fitting this battery, run one full discharge until the laptop hibernates at cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap on this platform.
BIOS reporting poor battery health immediately after installing a new cell
The T430u's BIOS reads health data from the battery's EEPROM, which stores cycle count, charge history, and rated capacity from the previous cell. When a new cell goes in, the BIOS compares the EEPROM data against measured voltage and flags a mismatch as poor health. This is a firmware read issue, not a fault with the new battery. Running one full discharge-to-hibernate followed by an uninterrupted full charge forces the BIOS to rewrite its learned capacity baseline. After two to three cycles, the health indicator normalises.
T430u shutting down suddenly at 20–30% charge shown
This happens when the cell voltage drops faster than the fuel gauge IC predicts under combined CPU and display load. The gauge was calibrated against the old, degraded cell and its voltage-to-capacity curve no longer maps correctly to the new chemistry. When the T430u draws peak current — during a burst workload or screen brightness spike — the new cell's actual terminal voltage briefly dips below the BMS cutoff threshold, triggering an immediate shutdown despite the display showing charge remaining. Calibrate by fully discharging to automatic hibernate cutoff, noting the reported percentage at shutdown, then charging to 100% without interruption. Repeat twice. The fuel gauge IC recalibrates its curve to the new cell, and the shutdown threshold aligns correctly — target is a stable cutoff below 5% shown.