About this replacement
Toshiba Satellite C800 / C805 Series — 10.8V Li-ion Replacement Battery (PA5023U-1BRS)
This is a 10.8V, 4400mAh (47.52Wh) lithium-ion battery for the Toshiba Satellite C800, C800D, C805, and C805D series laptops. It replaces OEM part numbers PA5023U-1BRS through PA5027U-1BRS, PABAS259–263, and PA5110U-1BRS. It slots into the same bay as the original and connects via the same multi-pin connector.
- Satellite C800 and C805 platform fit: These models share a common battery bay geometry, connector pinout, and BMS communication protocol across the C800, C800D, C805, and C805D variants — that is why one cell covers all of them. The voltage rail and pin assignments are identical across the range.
- Bench tested on actual hardware: We ran this cell on a Satellite C805 and confirmed the BMS handshake completed correctly. The charger recognised the battery, accepted a full charge cycle, and the protection circuit triggered cleanly at low-voltage cutoff.
- First-cycle calibration on the C800 series: After fitting, run the laptop on battery until it hibernates at low charge, then plug in and charge to 100% without interruption. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap.
Why the Satellite C800 shuts down at 20–30% after a battery swap
The Satellite C800's fuel gauge IC builds a charge map against the old cell's wear curve. When a new cell goes in, that map is wrong — the IC thinks the voltage floor is higher than it is. Under full CPU and display load, the laptop sees what it calculates as a critically low state of charge and forces a shutdown. Running one full discharge-to-hibernate cycle followed by an uninterrupted charge to 100% lets the IC re-map against the new cell. After two or three cycles, shutdowns at false percentages stop.
BIOS reporting the replacement battery's Wh rating incorrectly in system info
Toshiba's BIOS reads Wh data from EEPROM stored in the battery pack, not from live cell measurement. The EEPROM on a replacement cell carries the rated specification at manufacture — 47.52Wh — while the original pack's EEPROM may have written a degraded figure over time. If the BIOS shows a different Wh value than expected, that is an EEPROM mismatch, not a fault with the cell. Check the value under Control Panel → Power Options → Battery details after completing one full calibration cycle.