Compaq Presario CQ320 Replacement Battery 10.8V 6600mAh

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

This is a 10.8V, 6600mAh (71.28Wh) Li-ion battery for the Compaq Presario 320, 321, 325, and 326 notebook series. It slots into the standard underside battery bay and connects via the original locking latch and multi-pin connector. Voltage and connector pinout match the OEM specification for these models.

• Presario 320-series platform fit: The 320, 321, 325, and 326 share the same 10.8V battery rail, identical connector housing, and BMS handshake protocol — that is why one cell covers all four models. The BMS communicates state-of-charge data to the HP/Compaq EC firmware over the SMBus lines in the connector.
• Bench tested on actual hardware: We ran this cell on a Presario CQ320 and confirmed the BMS negotiated correctly with the embedded controller, charge current stepped down properly at 95%, and the system exited charge-only mode without error flags.
• First-cycle recalibration on the CQ-series: After fitting, let the laptop discharge fully until it hibernates on its own, then charge uninterrupted to 100% without interruption. This forces the EC to relearn the cell's capacity curve and clears the inaccurate "Consider replacing your battery" warning that appears after every cell swap on this platform.

Why the Presario 320 BIOS reports poor health immediately after fitting a new cell

The Compaq EC reads battery health from EEPROM data stored on the BMS board, not from live cell voltage. When a new cell is installed, the EEPROM still carries the degraded charge-cycle count from the old pack. The EC compares that stored data against the expected new-cell baseline and flags a mismatch as "poor health." Running one full discharge-to-hibernate followed by a complete uninterrupted charge resets the learned values and clears the warning.

Presario 320 shutting down at 20–30% charge shown on screen

This happens when the fuel gauge IC has not yet calibrated against the new cell's actual voltage curve. The IC is still using the old cell's droop profile, so it misreads the remaining charge and triggers a low-voltage shutdown too early. It is not a fault with the replacement cell. Run two full discharge-to-hibernate cycles followed by full uninterrupted charges — by the third cycle the fuel gauge IC will track accurately down to the correct cutoff near 10.8V depleted.