There is no universal waiting time. On a system that stores the password in battery-backed CMOS/RTC memory, 15–30 seconds may be enough. Other procedures require disconnecting every power source and holding the power button for at least 60 seconds. If the password is stored in nonvolatile firmware, a security chip, or the drive itself, leaving the battery out overnight will not remove it.
Before opening the computer, identify which password is being requested and follow the exact procedure for its model.
First identify what “PW” means
A prompt before Windows loads is not necessarily a CMOS password. Its location usually indicates the recovery path:
| Prompt or credential | Can a CMOS reset clear it? | Qualification |
|---|---|---|
| BIOS/UEFI setup password | Sometimes | Depends on the manufacturer, model, firmware generation and storage method. |
| BIOS administrator or supervisor password | Sometimes, often not | Business systems may retain it outside ordinary CMOS. |
| Power-on password | Sometimes | Model-specific. |
| Hard-drive or SSD password | Generally no | It belongs to the drive’s security mechanism; forgetting it may make the data inaccessible. |
| Windows or Microsoft-account password | No | Use Windows or account recovery instead. |
| BitLocker or FileVault recovery credential | No | A firmware reset is not a substitute for the recovery key. |
- A prompt before the manufacturer logo or operating-system boot is likely firmware, power-on or drive related.
- A Windows sign-in screen is an operating-system or account credential.
- A prompt after selecting a particular drive or boot device may be a drive password.
- A password requested only inside BIOS/UEFI setup is usually a setup, administrator or supervisor password.
What the CMOS battery actually does
The coin cell helps preserve the real-time clock and selected firmware configuration values while the computer is unplugged. Clearing that memory can restore the date, time, boot order and hardware settings to defaults. ASUS describes RTC memory as containing items such as date, time, BIOS password and setup parameters, but that describes a platform’s reset mechanism—not a guarantee that every modern password is stored there. See the ASUS clear-CMOS explanation.
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The battery does not store the BIOS firmware itself. Firmware normally remains in nonvolatile flash memory, and newer systems can keep security credentials in flash, an embedded controller, a security chip or the storage device.
How long should it be disconnected?
Use the manufacturer’s model-specific instructions whenever possible. Published procedures differ:
| Documented example | Timing |
|---|---|
| Dell XPS 13 9310 manual | Remove the coin cell for 15–30 seconds, then replace it. |
| HP generic desktop procedure | Disconnect all power and hold the power button for at least 60 seconds; repeat for 120 seconds if the BIOS clock does not reset to 00:00. |
| Supported Dell desktop RTCRST procedure | Apply the documented jumper reset for 10 seconds. |
These are examples, not a universal specification. The important step is removing every source of power and discharging residual energy; waiting longer does not defeat a password stored outside resettable CMOS.
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Fallback procedure for an accessible desktop battery
Use this only when the service manual permits battery removal. HP stresses that board-specific instructions take priority.
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- Unplug AC power and switch off or disconnect the power supply if applicable.
- Disconnect the main battery if the computer has one.
- Consult the service manual, open the case and identify the CMOS/RTC cell. Do not short random pins.
- Remove or unplug the cell.
- Hold the computer’s power button for at least 60 seconds (the HP generic discharge interval).
- Leave the cell disconnected for roughly 30 seconds to several minutes unless the manual specifies another interval. Overnight removal is not inherently better.
- Reinstall the cell with the correct polarity, reconnect the main battery and AC power, and start the computer.
- Enter BIOS/UEFI if possible, load defaults, set the date and time, restore required boot and storage settings, and save.
- Test whether the original prompt has changed.
Prefer a documented clear-CMOS control when available
Desktop motherboards may provide a CLR_CMOS, CLRTC, CLEAR or RTCRST jumper, a clear-CMOS button, or a separate password-clear jumper. These are usually faster and avoid handling the coin cell, but they remain model-specific and may reset settings without removing a security credential. Dell documents separate RTCRST and PSWD procedures and notes that the jumpers are not present on every system. ASUS directs owners to the exact motherboard manual.
Record these settings before resetting them:
- SATA mode, such as AHCI or RAID
- UEFI versus legacy/CSM boot mode
- Secure Boot state
- XMP/EXPO or other memory profiles
- Virtualization, fan-control and custom boot-order settings
Laptop warnings
Do not blindly open a laptop to remove its coin cell. The RTC battery may be wrapped, wired to a plug, soldered, hidden under shielding or inaccessible without substantial disassembly. The internal main battery may continue powering the embedded controller, and security state may be retained independently of the cell. Dell notes that RTCRST and PSWD jumpers are not available on Dell laptops; the method depends on the exact model. HP also notes that recovery behavior can differ on systems with protections such as Sure Start.
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For a business laptop, inaccessible battery or supervisor password, use the manufacturer’s support process. It may require proof of ownership, authorized service or a board replacement.
What a successful reset changes
- The date and time may revert to an old default or
00:00. - You may see “CMOS checksum error,” “time and date not set” or “defaults loaded.”
- Overclocking, memory profiles, fan settings, virtualization and custom boot order may be lost.
- The computer may stop booting until SATA/RAID, UEFI, Secure Boot or storage-controller settings are restored.
Dell explains that a battery-based reset returns BIOS settings to factory defaults; changed settings must be entered again.
If the password remains
- Verify that AC power, the main battery and the CMOS cell were all disconnected.
- Confirm that you disconnected the motherboard’s RTC cell—not merely a removable system battery.
- Repeat the exact procedure in the model’s service manual once.
- Use the documented clear-CMOS button or jumper if the model provides one.
- Look for an authorized password-clear or recovery process.
- Contact the manufacturer or an authorized service provider with proof of ownership.
Lenovo warns that clearing CMOS may not remove a forgotten supervisor password, depending on BIOS settings. It also states that a forgotten hard-disk password cannot be removed or used to recover the drive’s data. Do not rely on random “master password” sites or undocumented motherboard shorting instructions.
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Common questions
Will a new CR2032 reset a forgotten BIOS password?
No. A replacement cell fixes loss of date and settings caused by a weak battery; it does not change where a credential is stored.
Will removing the battery erase my files?
A CMOS reset normally changes firmware settings, not operating-system files. Incorrect settings can prevent booting, however, and a drive password is a separate security issue.
What if the computer now says “no boot device”?
Enter BIOS/UEFI and restore the previous boot mode, SATA/RAID mode, storage-controller configuration and boot order. If you did not record them, consult the model manual or an authorized technician.
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What if the laptop has no removable CMOS battery?
Stop disassembly and follow the manufacturer’s documented recovery procedure. Some laptops require an external reset control or authorized service.
The Bottom Line
Bottom line: follow the exact model procedure. A 15–30-second battery removal can work on some Dell systems; a fully disconnected system with a 60-second power-button discharge is a sensible fallback where the manual permits it. More waiting will not clear a password stored in nonvolatile firmware, security hardware or the drive.
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