Dell Inspiron 1521 Replacement Battery 11.1V 6600mAh 312-0575

Dell Inspiron 1521 / 1520 / 1721 / Vostro 1500 — 11.1V Li-ion Replacement Battery (312-0575)

This is an 11.1V 6600mAh (73.26Wh) lithium-ion battery for the Dell Inspiron 1521, 1520, 1721, and Vostro 1500 laptops. It replaces OEM part numbers 312-0575, GK479, FP282, FK890, NR239, GR995, and related cross-references. Direct swap with the original cell — same connector, same BMS handshake protocol.

• Inspiron 1520 / 1521 / 1721 and Vostro 1500 platform fit: These four models share a common battery bay geometry, 11.1V voltage rail, and identical Dell BMS communication protocol. One cell covers all four without modification.
• Bench tested on actual hardware: We ran this cell on an Inspiron 1521 and a Vostro 1500. The BMS handshook correctly on both units, BIOS recognised the battery without errors, and charge current stepped down cleanly at the expected topping threshold.
• First-install calibration on Dell systems: After fitting this cell, run the laptop on battery until it hits hibernate cutoff — do not interrupt it. Then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health or low-capacity warning that appears after any cell swap on these Dell models.

BIOS reporting poor battery health immediately after fitting a new cell

Dell's BIOS reads EEPROM data embedded in the battery's fuel gauge IC to assess health. When a new cell arrives, the EEPROM cycle count is zero and the rated Wh figure may not yet match what the BIOS expects from a learned profile. The system flags this mismatch as degraded health even though the cell is new. One complete discharge-to-hibernate followed by a full uninterrupted charge gives the BIOS enough data to rebuild its learned capacity profile and clear the warning.

Laptop shuts down abruptly at 20–30% charge shown on screen

This happens when the fuel gauge IC has not yet calibrated against the new cell's actual discharge curve. The OS gauge is still working from the old cell's learned data, so the reported percentage drifts well above the real remaining voltage. Under full CPU and display load the cell hits its low-voltage cutoff before the gauge reaches 0%, causing an immediate shutdown. Run two or three full discharge-to-hibernate and full-charge cycles — the fuel gauge IC re-maps its curve against the new cell and the shutdown point drops back to below 5% reported. After calibration, resting voltage at 20% reported should read approximately 10.8V at the pack terminals.