HP Presario 300 CMOS Battery 468824-001 3V 75mAh

HP Presario 300 Series — 3V Lithium CMOS Backup Battery (468824-001)

This is a 3V 75mAh lithium coin cell that fits the CMOS/RTC socket on HP Presario 300, 305, 306, and Pavilion DV3000 series motherboards. It powers the real-time clock circuit and SRAM that hold BIOS settings, date, and time when the laptop is unplugged or shut down. When it drops below retention voltage, those settings vanish on every power cycle.

• Presario 300 / 305 / 306 and Pavilion DV3000 socket fit: These models share the same motherboard CMOS socket footprint and connector spring geometry, accepting the same 25.58 × 20.30 × 2.80mm cell. The BMS here is passive — the cell directly backs the RTC and CMOS SRAM with no active regulation between them.
• Bench tested on actual hardware: We seated this cell in a Presario 300 board and confirmed the RTC circuit held date and time across a full AC removal cycle. Open-circuit voltage measured 3.0V on arrival, within the expected range for a fresh lithium cell.
• First boot after replacement: After installing, enter BIOS immediately and set the correct date and time, then save and exit. The RTC circuit resets to a factory default when the old cell is removed — even a brief gap without power clears the clock register, so saving correct values is a required step, not optional housekeeping.

BIOS clock resetting to 2000 after every power cycle

The Presario 300's RTC circuit draws continuously from the CMOS cell whenever AC power is absent. Once the cell drops below approximately 2.8V, it can no longer maintain the voltage rail the RTC needs to hold register values. The clock resets to a default date — typically January 1, 2000 — on every cold boot. Replacing the cell and setting the correct date in BIOS resolves this immediately; the symptom does not return unless the new cell is also depleted or seated incorrectly.

CMOS checksum error on boot screen after cell swap

A checksum error on the POST screen means the BIOS has detected that stored configuration data no longer matches its own checksum — a sign the CMOS SRAM lost power completely during the cell swap. This is expected when the old cell was fully dead before removal, because even a brief interruption clears SRAM contents. Enter BIOS setup immediately after boot, restore any custom settings such as boot order or SATA mode, then save and exit. The error will not reappear as long as the new cell holds above 2.8V.