Toshiba Libretto U100 Replacement Battery 10.8V 3400mAh

Toshiba Libretto U100 / U105 — 10.8V Li-ion Replacement Battery (PA3442U-1BRS)

This is a 10.8V, 3400mAh (36.72Wh) Li-ion replacement battery for the Toshiba Libretto U100 and Libretto U105 ultra-portable notebooks. It replaces OEM part numbers PA3442U-1BRS and PABAS062. The Libretto U100 and U105 share the same battery bay, connector, and BMS handshake protocol, so one cell covers both models.

• U100 and U105 compatibility: Both models use the same battery housing, three-pin connector, and SMBus communication line. The BMS in each model reads the same EEPROM chemistry flags, so the cell installs and initialises identically on both.
• Bench tested on actual hardware: We ran the cell through full charge and discharge cycles on a Libretto U100 unit. The BMS accepted the cell without fault codes, charge current ramped correctly in CC/CV stages, and the protection circuit triggered cleanly at the low-voltage cutoff threshold.
• First-cycle calibration on the Libretto: After installation, run one full discharge to hibernate cutoff, then charge uninterrupted to 100% without using the machine mid-cycle. This gives the Libretto's fuel gauge IC a clean reference point against the new cell and clears the inaccurate battery health warning that appears in Toshiba's power utility after every cell swap.

Why the Libretto U100 BIOS reports poor battery health after a cell swap

The Libretto U100 stores battery health data in the EEPROM of the original cell. When a new cell goes in, the BIOS reads cycle count and capacity history that no longer matches the actual chemistry. The system flags the battery as degraded because the EEPROM data is stale, not because the new cell is faulty. Running a complete discharge-to-hibernate then uninterrupted full charge resets the learn cycle and lets the BIOS build a fresh capacity baseline from the new cell's actual performance.

Libretto U100 shutting down at 20–30% charge shown on screen

This happens when the fuel gauge IC is still calibrated against the worn-out original cell. The old cell had a steep voltage cliff at low charge, and the IC learned to cut power at that point. A new cell with healthier chemistry holds voltage longer, but the uncalibrated gauge still triggers the shutdown at the old threshold. Run two full discharge-to-hibernate cycles followed by uninterrupted charges to 100% — after the second cycle, the gauge recalibrates and the early shutdowns stop. If the problem persists after two cycles, check the BIOS battery settings and confirm charge mode is not locked at a custom cutoff value.