About this replacement
Toshiba Dynabook Qosmio GXW/70LW — 10.8V Li-ion Replacement Battery (PA3729U-1BAS)
This is a 10.8V, 4400mAh (47.52Wh) Li-ion replacement battery for the Toshiba Dynabook Qosmio GXW/70LW and related Qosmio models. It slots directly into the battery bay and restores portable operation after the original cell has degraded. OEM part numbers PA3729U-1BAS, PA3729U-1BRS, PA3730U-1BAS, PA3730U-1BRS, and PABAS207 all cross-reference this cell.
- Qosmio series compatibility: The GXW/70LW, Qosmio 90LW, 97K, and 97L share the same 10.8V battery rail, connector pinout, and BMS handshake protocol — which is why a single cell covers this entire lineup without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on Qosmio-series hardware. The BMS negotiated correctly with the system board, charge current stepped down at the expected voltage threshold, and the protection circuit tripped cleanly at low-cell cutoff.
- Post-install calibration on the Qosmio: After fitting this battery, 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 appears after every cell swap on these Toshiba models.
Why the Qosmio shuts down at 20–30% charge shown
Under combined CPU and display load, the Qosmio draws enough current to create a sharp voltage sag in the battery pack. When the cell voltage drops below the BMS cutoff threshold — even briefly — the system treats it as a dead pack and shuts down immediately. The state-of-charge percentage shown on screen is calculated by the fuel gauge IC, not measured in real time against that sag. A new cell and one full calibration cycle resets the fuel gauge's discharge curve so the reported percentage tracks the actual voltage more accurately.
BIOS reporting new battery health as "poor" or "replace battery" immediately after install
The Toshiba BIOS reads health data stored in the battery's EEPROM — and on a new replacement cell, that EEPROM does not yet carry the charge history the BIOS expects to see. The warning is a data mismatch, not a faulty cell. Run the full discharge-to-hibernate then uninterrupted charge-to-100% cycle once, and the BIOS learn cycle will write fresh baseline data to the EEPROM. After one complete cycle, the health warning clears on most Qosmio models.