Battery Storage Mode and how it affects the CMOS Battery shelf life
Сводка: This article discusses computers not able to power on after being turned off for a long period of time due to battery storage mode and it's impact on the CMOS (Complementary Metal Oxide Semiconductor) battery shelf life. ...
Инструкции
Before You Begin
For generic troubleshooting steps for battery issues, see the Dell Battery Support library page
Quick Answer
If a Dell laptop will not turn on after sitting powered off for a while, the main battery has likely entered Battery Storage Mode, a protective feature that limits power draw to preserve battery health. Plug in the AC adapter to wake the battery and boot the computer. If the system was off long enough to also drain the separate CMOS battery (~60 days), it will boot but show a "Time of date not set - please run setup program" error and have lost custom BIOS settings; you will need to manually re-enter any custom BIOS settings.
Applies To
- Product lines: Dell laptops and Dell Mobile Workstations.
- Component: Main system battery and CMOS (Complementary Metal-Oxide-Semiconductor) battery.
- Condition: Standard behavior on Dell laptops and mobile workstations manufactured since 2014.
- Does not apply to: Desktop towers with no internal rechargeable battery (CMOS battery behavior may still apply).
Definitions
|
Term |
Definition |
|---|---|
|
Battery Storage Mode |
An auto-protection feature in Dell batteries that limits power output and shuts the battery down after a period of non-use, preventing over-drain and preserving long-term battery capacity. |
|
CMOS battery |
A small, separate rechargeable battery inside the computer that maintains the system clock and custom BIOS settings when the computer is unplugged, and the main battery is depleted or in storage mode. |
Symptoms
A user may observe one or more of the following:
- The computer will not power on using the battery alone when it reaches a low-charge threshold or after up to three weeks of inactivity.
- The computer powers on only after the AC adapter is connected.
- After a prolonged period without AC power, the system boots but displays: "Time of date not set - please run setup program".
- Custom BIOS settings have reverted to defaults.
Cause
Main battery enters Storage Mode. To protect long-term battery health, Dell batteries automatically enter Storage Mode when either of these occurs:
- The battery charge level drops to a low threshold, or
- The computer has been unused for a maximum of three weeks.
Standard behavior on Dell laptops and mobile workstations manufactured since 2014 — it is not a defect.
CMOS battery depletes if storage continues. Once the main battery is in Storage Mode, the small CMOS battery takes over keeping the system clock and custom BIOS settings. A fully charged CMOS battery lasts approximately 60 days. After that, it depletes and the BIOS loses its custom settings.
Resolution
|
Step |
Action |
Purpose |
|---|---|---|
|
1 |
Connect the AC adapter to the computer. |
Wakes the main battery from Storage Mode so the system can boot. |
|
2 |
If the computer is stored for an extended period, power it on periodically and connect AC power to prevent CMOS battery depletion. |
Prevents the CMOS battery from fully draining and losing BIOS settings. |
|
3 |
If the "Time of date not set - please run setup program" message appears, press F2 to enter BIOS setup, verify the date/time, and reconfigure any required custom BIOS settings before exiting. |
Acknowledges that the CMOS battery was depleted; settings will need to be reconfigured. |
|
4 |
Leave the computer plugged in for a period after a long storage period. |
The CMOS battery is rechargeable and begins charging automatically once AC power is connected. |
|
5 |
Before placing a computer into long-term storage, charge the main battery fully. |
Maximizes battery shelf life during storage. |
Expected outcome: Once AC power is connected, the computer boots normally. Any BIOS settings lost due to CMOS battery depletion must be manually reconfigured; the CMOS battery itself recharges automatically and does not need to be replaced under normal circumstances.
Frequently Asked Questions
Q: Is this a hardware failure?
A: No. Battery Storage Mode is an intentional protective feature, not a fault.
Q: How long can my laptop sit unused before this happens?
A: The main battery may enter Battery Storage Mode when it reaches a low-charge threshold or after up to three weeks of inactivity. The CMOS battery can sustain settings for roughly 60 days after that.
Q: Will I lose data?
A: No. This affects power-on capability and BIOS/clock settings only, not stored data on the drive.
Q: Do I need to replace the battery because of this? A: No. Simply connecting the AC adapter resolves the symptom. Replacement is only warranted if the battery fails to charge or hold charge after being plugged in.
Q: My BIOS settings reset — is that permanent?
A: The reset happens once the CMOS battery has depleted after prolonged loss of power. Reconnecting AC power recharges the CMOS battery; you will need to manually re-enter any custom BIOS settings.