Fujitsu LIFEBOOK E5413 Replacement Battery 15.44V 3900mAh

Fujitsu LIFEBOOK E5413 — 15.44V Li-Polymer Replacement Battery (CP813249-01)

This 15.44V, 3900mAh (60.22Wh) Li-Polymer battery replaces the original cell in the Fujitsu LIFEBOOK E5413 and several related models including the LIFEBOOK U7312 and E4412 series. It matches the OEM voltage rail and connector so the BIOS handshake completes on first boot. Capacity figures are sourced directly from product data — not estimated from third-party listings.

• LIFEBOOK E5413, U7312, and E4412 compatibility: These models share the same 15.44V four-cell architecture, identical connector pinout, and the same BMS communication protocol — which is why one cell covers the full group. The BIOS expects a specific voltage range and EEPROM signature; this battery satisfies both without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a LIFEBOOK platform. The BMS reported a full charge without triggering the BIOS health warning, and the fuel gauge IC accepted the new cell data within two calibration cycles.
• Post-install calibration on LIFEBOOK firmware: After fitting this battery, run one full discharge until the laptop hibernates, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap.

BIOS reporting battery health as poor immediately after replacement

The LIFEBOOK firmware stores charge history and cell data in an EEPROM register tied to the old battery. When a new cell goes in, that register still holds stale data from the degraded pack, so the BIOS flags the new battery as unhealthy before it has run a single cycle. This is a firmware state issue, not a fault with the replacement cell. Running one full discharge-to-hibernate followed by an uninterrupted charge to 100% triggers the BIOS learn cycle and rewrites the register. After two to three cycles the health indicator updates to reflect the actual cell condition.

Laptop shutting down at 20–30% charge shown on screen

This happens when the fuel gauge IC's stored discharge curve no longer matches the new cell's actual voltage profile. The IC predicts shutdown too early because it is still referencing the old cell's degraded curve. Under full CPU and display load the voltage sag hits the cutoff threshold before the displayed percentage reaches zero. Perform two full calibration cycles — discharge to hibernate cutoff, then charge to 100% each time — and the fuel gauge IC will recalibrate against the new cell's actual voltage floor, typically around 14.0V at cutoff.