Toshiba Tecra S1 Replacement Battery PA3248 10.8V 6600mAh

Toshiba Tecra S1 — 10.8V Li-ion Replacement Battery (PA3248)

This is a 10.8V, 6600mAh Li-ion battery for the Toshiba Tecra S1 business notebook. It replaces OEM part numbers PA3248, PA3248U-1BAS, PA3248U-1BRS, PA3257, PA3257U-1BRS, and PA3257U-1BAS. Dimensions are 144.20 x 90.10 x 20.20mm — verify fitment against your existing cell before ordering.

• Tecra S1 battery bay fitment: Toshiba used the PA3248 and PA3257 part numbers across the same Tecra S1 chassis generation. Both share the same connector pinout, voltage rail, and BMS handshake protocol — this cell covers both.
• Bench tested on actual hardware: We cycled this cell through charge and load on the Tecra S1 platform. The BMS communicated correctly with the system board, accepted a full charge, and held voltage under sustained CPU and display load without tripping a protective cutoff.
• First-cycle calibration on the Tecra S1: After fitting, run the battery down until the laptop hibernates, then charge uninterrupted to 100%. This forces the Tecra S1 BIOS to complete its battery learn cycle and clears the false "poor health" warning that appears after any cell swap.

BIOS reporting battery health as poor after replacement

The Tecra S1 BIOS stores learned capacity data from the previous cell in its EEPROM. When a new cell is fitted, that stored data no longer matches, so the system flags the battery as degraded or unhealthy. This is a firmware state, not a fault with the new cell. Run one full discharge-to-hibernate cycle followed by an uninterrupted charge to 100% — the BIOS recalculates and overwrites the old health record.

Tecra S1 shutting down at 20–30% charge remaining

This happens when the fuel gauge IC has not yet calibrated against the new cell's actual charge curve. The gauge reports 20–30% remaining, but the cell has already hit its voltage cliff under combined CPU and display load, so the system shuts down to protect the hardware. It is not a faulty battery — it is an uncalibrated gauge. Complete two or three full discharge-to-hibernate then full-charge cycles to bring the fuel gauge into alignment with the new cell's true capacity.