Toshiba Satellite P20-304 Replacement Battery PA3291U-1BAS 14.8V 6600mAh

Toshiba Satellite P20-304 — 14.8V Li-ion Replacement Battery (PA3291U-1BAS)

This is a 14.8V 6600mAh Li-ion replacement battery for the Toshiba Satellite P20 and P25 series notebooks. It fits the Satellite P20-304, P20-134, P20-104, and P25-S508 among 34 additional confirmed models. The OEM part numbers are PA3291U-1BAS and PA3291U-1BRS.

• Satellite P20 and P25 series fit: All confirmed models on this platform share the same 14.8V four-cell voltage rail, the same physical connector pinout, and a compatible BMS handshake. The battery slots in without modification and the BIOS recognises the cell on first boot.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the P20 platform. The BMS held the charge cutoff correctly at full capacity and the protection circuit responded to over-discharge conditions without tripping prematurely under display-plus-CPU load.
• First-cycle recalibration on the P20: After installing, run one full discharge until the laptop hibernates on its own, then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell and clears the inaccurate health warning that appears after every cell swap on this platform.

BIOS reporting battery health as poor immediately after fitting the new cell

The Satellite P20 BIOS stores cycle count, capacity history, and health data in the old cell's EEPROM. When a new cell goes in, the BIOS reads no matching history and flags health as unknown or poor. This is not a fault with the replacement cell. Run one full discharge-to-hibernate followed by an uninterrupted charge to 100% — the BIOS learn cycle rewrites its health estimate against the new cell's actual data. The warning clears after one to two completed cycles.

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

This happens when the cell voltage drops below the BMS cutoff threshold under combined CPU and display load before the fuel gauge IC catches up. The fuel gauge was calibrated to the old, degraded cell and its voltage-to-capacity curve no longer matches the new chemistry. The fix is to let the laptop discharge fully to hibernate-cutoff twice in a row — this gives the fuel gauge IC enough data to re-map the voltage cliff on the new cell. After two full cycles the reported percentage at shutdown should drop to 3–5% rather than 20–30%.