About this replacement
Toshiba Dynabook CX/45C Series — 10.8V Li-ion Replacement Battery (PA3593U-1BAS)
This is a 10.8V, 4400mAh (47.52Wh) Li-ion battery for the Toshiba Dynabook CX series. It fits the CX/45C, CX/45D, CX/45E, CX/47C, and over 100 additional Dynabook CX variants sharing the PA3593U-1BAS / PA3594U-1BRS platform. The connector, BMS handshake protocol, and cell configuration match the original factory specification.
- Dynabook CX platform compatibility: These CX models share a common battery bay form factor, 10.8V three-cell series configuration, and the same BMS communication line. Any variant in this cluster that accepts PA3593U-1BAS, PA3594U-1BRS, or PABAS111 will seat and communicate correctly with this cell.
- Bench tested on actual hardware: We ran this battery through charge and discharge cycles on a CX-platform unit. The BMS reported correct voltage at each state-of-charge threshold, charge termination fired at the expected full-cell voltage, and no protection trips occurred during load transitions.
- First-install calibration on the Dynabook CX: After fitting, discharge the laptop fully to hibernate-cutoff — do not manually power off — then charge uninterrupted to 100%. This forces the Dynabook's fuel gauge IC to map its state-of-charge curve against the new cell and clears the inaccurate health warning that appears in Toshiba's battery utility after every cell swap.
Why the Dynabook CX shuts down at 20–30% after a battery swap
The Dynabook's fuel gauge IC retains state-of-charge data from the old, degraded cell. When a new cell is installed without running a calibration cycle, the IC's discharge curve is misaligned — it triggers a low-battery shutdown well before the cell is actually depleted. This is not a fault with the replacement cell. Running one full discharge to hibernate-cutoff followed by an uninterrupted charge to 100% re-anchors the IC's curve to the new cell's actual capacity. After two or three full cycles, the gauge reading stabilises.
BIOS showing battery health as "poor" or capacity as 0% on a new cell
The Toshiba BIOS reads health data from EEPROM registers that store cycle count and rated capacity from the previous battery. On first install, these values haven't been updated to reflect the new cell, so the BIOS reports poor health or zero capacity. This is an EEPROM data lag, not a defective battery. Boot into the Toshiba Battery Utility (or run a full learn cycle via Windows Battery Report), complete one full discharge-to-hibernate and charge-to-100% pass, and the BIOS will re-read the updated register values — health should report correctly within one to two cycles.