Toshiba Tecra S1 Replacement Battery PA3248U 10.8V 4400mAh

Toshiba Tecra S1 — 10.8V Li-ion Replacement Battery (PA3248U)

This is a 10.8V, 4400mAh (47.52Wh) Li-ion battery for the Toshiba Tecra S1 notebook. It replaces OEM part numbers PA3248U, PA3248U-1BAS, and PA3248U-1BRS. The Tecra S1 is a business-class laptop, and this cell matches the original voltage rail and connector spec.

• Tecra S1 compatibility: The S1 series shares a single battery bay spec across its production run — same 10.8V rail, same connector pinout, same BMS handshake protocol. All three PA3248U variants are electrically identical; Toshiba issued suffix codes only for regional SKU tracking.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the Tecra S1 platform. The BMS handshake completed correctly, charge termination triggered at the expected voltage ceiling, and the protection circuit responded normally to load transitions during CPU and display stress.
• First-cycle calibration on the Tecra S1: After fitting this battery, run one full discharge to the hibernate 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 fitting a new cell

The Tecra S1 BIOS reads health data from EEPROM registers that were last written by the old cell. When a new battery lands in the bay, those registers still hold the degraded values from the previous pack. The system flags the battery as poor or unknown because it is comparing live voltage against stale EEPROM history, not against the new cell's actual chemistry. Running a full discharge-to-hibernate followed by an uninterrupted charge to 100% forces the BIOS learn cycle to overwrite those registers. After one complete cycle, the health indicator should clear and report correctly.

Laptop shuts down abruptly while the gauge still shows 20–30% remaining

This is a voltage cliff, not a capacity problem. Under combined CPU and display load, current draw spikes and the cell voltage drops faster than the fuel gauge IC can update its estimate. When cell voltage falls below the BMS cutoff threshold — typically around 9.0V for a 10.8V three-cell pack — the protection circuit cuts output instantly, regardless of what percentage the OS is showing. The fuel gauge IC needs two to three full calibration cycles against the new cell before its discharge curve model catches up. Run three complete discharge-to-hibernate and full-charge cycles, and the shutdown point will shift to match the real remaining capacity.