Toshiba Satellite C40 Replacement Battery 10.8V 4400mAh PA5108U

Toshiba Satellite C40 Series — 10.8V Li-ion Replacement Battery (PA5108U-1BRS)

This is a 10.8V, 4400mAh (47.52Wh) Li-ion battery for the Toshiba Satellite C40 series notebook. It fits the C40-AD05B1, C40-AT15B1, C40-AS20W1, C40-AT19W1, and over two dozen additional C40 variants. OEM cross-references include PA5108U-1BRS, PA5109U-1BRS, PA5110U-1BRS, PABAS271, PABAS272, and PABAS273.

• C40 series compatibility: All covered models share the same 10.8V rail, identical connector pinout, and a common BMS communication protocol. Toshiba used this same battery housing across the C40 lineup regardless of regional suffix — the AD05B1, AT15B1, AS20W1, and AT19W1 all pull from this same pack specification.
• Bench tested on actual hardware: We ran this cell on a C40-series board and confirmed the BMS handshake completes correctly. The charge controller accepted the pack without fault codes, and voltage held steady through a full charge cycle with no thermal interruption.
• First-cycle conditioning on C40 hardware: After installing, run the laptop down to hibernate cutoff on battery only — no AC — then charge it uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell's actual capacity curve and clears the inaccurate health warning that appears after every cell swap.

BIOS reporting poor battery health immediately after fitting a new cell

The Satellite C40 BIOS reads health data from the battery's EEPROM, not from live voltage measurements. When a new cell arrives, its EEPROM contains factory-default data that the BIOS has never seen before, so it flags the pack as unknown or degraded. This is not a fault with the replacement cell. Running one full discharge-to-hibernate followed by an uninterrupted charge to 100% allows the BIOS learn cycle to write fresh data against the new cell. After one or two calibration cycles, the health indicator will update to reflect actual capacity.

Laptop shuts down abruptly at 20–30% charge shown

This symptom appears when the fuel gauge IC hasn't yet calibrated against the new cell's voltage curve. The gauge shows 25% remaining, but the cell voltage is already hitting the BMS low-voltage cutoff under the combined load of the CPU, display, and storage. The old cell's discharge profile was mapped in firmware — the new cell needs a fresh reference point. Run two complete discharge cycles to hibernate cutoff with the screen at full brightness and a CPU load active, then recharge fully each time. After the second cycle, the gauge readout and actual cutoff voltage should align to within a few percent.