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I have a Dell Latitude 7430 laptop computer. About two years ago, I installed Windows 11 on it with disk encryption enabled. Then I stored it without connecting the charge for a 2-year long duration.

Today, I wanted to boot it up but found that it didn't boot due to "inaccessible boot device" error. The BIOS also had lost its date and time. I had to go into BIOS, set the date and time, and then change secure boot "ON", and to change the SATA mode from RAID into AHCI.

The computer is rather new, from 2023. So if it had a lithium coin battery, I don't think its charge would run out this quickly. Also the main battery of the laptop had 60% charge when I used it after being unused for 2 years.

So my only plausible explanation is that it has a secondary rechargeable battery for storing BIOS settings, and that secondary rechargeable battery is inadequate for long storage durations.

But can it really be the case that maintaining BIOS settings would require so much current that even a small secondary rechargeable battery would run out its charge?

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  • How much voltage was left in the coin battery? Edit your question Commented yesterday

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"BIOS also had lost its date and time." Clocks require continuous power, and some CMOS memory, as well, though just the tiniest trickle, measured in microwatts. There is a Li-ion coin cell, such as this from Amazon or this from Parts People that runs the clock, and also maintains the BIOS CMOS storage.

There are videos showing how to access and change the CMOS cell, such as this on YouTube for the similar Dell 7400. In short,

  • Remove the screws holding the bottom of the shell,
  • Remove the screws holding the large power battery,
  • Access the Li coin cell underneath and replace it.
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Most computers have a separate battery that maintains the BIOS storage. These can last for years, but there are too many factors involved to say they will last for years.

A computer sitting disconnected from any power will drain small amounts over time, and eventually this will result in the symptoms you have observed.

It could also be some minor fault on the system, but that is only possible, not probable. The most likely culprit is that what energy was on the system to maintain these settings has fully drained.

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Searching for what kind of battery my computer has for BIOS resulted in me finding https://www.amazon.com/Rome-Tech-CMOS-Battery-Latitude/dp/B08H9ZTXCL

So it appears there's a secondary small li-ion battery. 225 mAh, similar in capacity to coin cell lithium primary batteries.

However, those coin cells generally last for 10 years. This didn't last even 2 years. So, I assume that Dell is wasteful with the energy that is contained in this battery, which is possible only because this small battery is rechargeable.

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  • 1. The Dell 7430 was first sold in April, 2022. Though you might have purchased it in 2024, the machine might be two years older. 2. As long as the main battery is charged, it might provide power for the clock. By leaving it uncharged for two years, both batteries were likely damaged -- look for the main battery to soon need replacement. Commented yesterday
  • There is also no promise the battery was fresh when it was installed. In normal circumstances, a computer being unpowered for only only months, not years, this setup is fine. Computers are not generally intended or designed to sit unpowered for multiple years without some minor maintenance required to get them up into a running state again. Commented yesterday
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    "However, those coin cells generally last for 10 years." - Ten years sounds more like the shelf life of a battery than any possible working life with an unspecified load. The battery will self-discharge even when unused and sitting on a shelf with stable environmental conditions. You're making a faulty conclusion based on a flawed assumption. Commented yesterday

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