Compaq 320 Laptop Replacement Battery 10.8V 4400mAh

Compaq 320 / 321 / 325 / 326 — 10.8V Li-ion Replacement Battery (587706-751)

This 10.8V, 4400mAh Li-ion cell replaces the original battery in the Compaq 320, 321, 325, and 326 notebook series. It matches OEM part numbers including 593572-001, HSTNN-IB1A, HSTNN-LB1A, and HSTNN-CB1A. If your original cell no longer holds charge or the laptop won't run unplugged, this is the direct cell-for-cell swap.

• 320/321/325/326 platform fit: These four models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — one cell covers all four. The 10.8V nominal voltage rail and six-cell configuration are identical across the group, so there's no adapter or firmware workaround needed.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on a 320-series unit. The BMS completed its initialisation handshake, charge current was accepted without fault, and the cell held voltage under sustained CPU and display load without tripping the low-voltage cutoff prematurely.
• First-cycle calibration for this notebook: After fitting, run one full discharge until the laptop hibernates on low battery, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after a cell swap on this platform.

BIOS reporting poor battery health immediately after swap on the 320 series

The 320's BIOS reads health data from EEPROM stored on the old cell. When a new cell installs, the BIOS compares the new cell's charge history against the previous EEPROM record and flags a mismatch as degraded health. This is a firmware read error, not a fault with the replacement cell. Running one full discharge-to-hibernate followed by an uninterrupted charge to 100% prompts the BIOS to rewrite its battery data against the new cell. After one or two full cycles, the health indicator corrects itself.

Laptop shuts off at 20–30% charge shown on the new cell

This happens because the fuel gauge IC hasn't yet calibrated against the new cell's actual voltage curve. The gauge inherited discharge data from the old battery and miscalculates the remaining capacity threshold. Under full CPU and display load, the cell hits its voltage floor before the OS registers 0% — so the laptop cuts out mid-use. Complete two full discharge-to-hibernate and charge-to-100% cycles without interruption. By the second cycle, the fuel gauge IC recalibrates and the shutoff point drops back to the correct low-voltage floor near 10.5V per cell group.