Technician helping fix an Acer computer that needs frequent restart

Steve H.

Reviewed for technical accuracy

Specialities: Desktop PCs (Dell/HP/Lenovo/custom builds), BIOS/UEFI setup & boot order issues, CMOS/RTC battery (CR2032) problems, “time resets” & date errors

CMOS battery replacement on a desktop — wrong date/time, BIOS reset, “CMOS battery low”, CR2032, boot order & POST warnings

Technician avatar Technician
Hi! We’ll handle this calmly and safely.

When a desktop computer keeps losing the time/date, forgets BIOS settings, or shows messages like “CMOS battery low”, “CMOS checksum error”, or “Press F1 to continue”, the most common cause is the small CMOS/RTC coin-cell battery (often a CR2032) getting weak.

Before we talk about opening the case, I want to confirm it’s not just Windows time settings. A quick set of questions (no risky steps):
• Is this a desktop tower (not a laptop), and do you know the brand (Dell/HP/Lenovo) or is it a custom build?
• What exactly changes: time/date wrong, boot order resets, fan settings reset, or “no boot device” until you fix BIOS?
• Does the issue happen after the PC has been fully unplugged or after a power outage?

I’m asking because I don’t want you to do anything that could make it worse. We’ll start with the least risky checks first.
Customer
It’s a desktop tower, older one. I’m not sure the brand, maybe a custom one. The time is wrong almost every morning, sometimes the date jumps back. I also got a black screen that said something about BIOS settings being reset. I’m worried it’s a virus or something serious.
Technician avatar Technician
I understand the worry — but this particular symptom (time/date jumping backward + BIOS reset message) is usually hardware/firmware memory, not malware.

Think of it like a tiny watch battery on the motherboard. When it weakens, the PC can forget the correct clock and some BIOS/UEFI settings whenever it loses wall power.

Two safe checks that don’t require opening anything:
• When the PC is on, does the Windows clock stay correct during the day, and only become wrong after being off overnight?
• Is the computer plugged into a power strip that gets switched off at night, or does it get unplugged?

These answers help separate “Windows time sync” from “CMOS/RTC battery not holding.”
Customer
During the day the time is fine. It’s after it’s been off. And yes, I turn off the power strip sometimes because I don’t like leaving things on. Could that cause it? Also I saw “Press F1 to run setup” once.
Technician avatar Technician
That’s a strong clue. Turning off the power strip is fine — a healthy desktop should still remember time/settings. If it doesn’t, the coin-cell battery is often the reason.

“Press F1 to run setup” commonly appears when BIOS detects a reset or a clock problem. Seniors often describe it as “my computer panics at startup.” You’re not alone — it’s a very common aging-desktop issue.

Quick question: when that screen appears, do you also see words like CMOS, RTC, battery low, or checksum?
Customer
I remember “CMOS” and maybe “checksum.” It’s scary because it looks like an error screen. Sometimes after that, Windows takes longer to start. I’m afraid to press the wrong key and break something.
Technician avatar Technician
You’re doing the right thing by being cautious. I don’t want you pressing random keys on that screen either.

Here’s the safe logic: a weak CMOS battery can reset the BIOS clock and sometimes the boot order. If boot order changes, the desktop may hesitate, show “no boot device,” or need F1/F2/DEL prompts before Windows starts.

Another safe question (no changes yet): have you ever seen “Boot device not found” or did it ever try to boot to the wrong thing (like a USB drive)?
Customer
One time it said it couldn’t find a boot device, then after I restarted it worked. I don’t use USB drives much. I just want it to start normally and keep the correct time.
Technician avatar Technician
That fits the pattern: clock resets + occasional boot order confusion points to CMOS/RTC battery rather than Windows itself.

Trust moment: we’re not going to jump straight to “open the PC and poke around.” First, we can confirm it with a simple, low-risk test you can do with the case closed:
• Set the correct time in Windows, shut down normally, then turn off the power strip for 10–30 minutes.
• Power back on and check whether the time is still correct.

If it’s wrong after that short power cut, it strongly suggests the motherboard isn’t holding the clock without that coin-cell battery.
Customer
I can do that. If it is the battery, is it expensive? And is it dangerous to replace? I’m older and my hands aren’t as steady. I don’t want an electric shock.
Technician avatar Technician
Completely fair concerns. The coin-cell itself is usually inexpensive (often labeled CR2032), but I’m more focused on doing it safely and comfortably for you.

Safety notes (simple and important):
• A desktop must be shut down and unplugged before any case is opened.
• We avoid touching other parts, and we take basic static precautions.
• If you’re not comfortable opening the case, it’s absolutely reasonable to have a friend or a local shop do just the battery swap — it’s a common request.

Also, I don’t want you to replace it blindly if the symptoms are actually Windows time sync. That’s why we confirm first with the quick power-strip test.
Customer
Okay. Another thing: sometimes Windows says the time zone changed or the time is not synchronized. Could that be the same issue?
Technician avatar Technician
It can be related, but they’re not identical.

• Windows time sync issues usually show up while Windows is running (internet/time server settings).
• A weak CMOS/RTC battery usually shows up after the computer has been off and power was removed — the BIOS clock starts wrong, then Windows “notices” and tries to correct it later.

That’s why your “works during the day, wrong after being off” detail is so important. It points more strongly to the battery holding the hardware clock.
Customer
If I do replace the battery, will I lose files or photos? And will it change anything important?
Technician avatar Technician
Good question, and I’m glad you asked before doing anything.

Replacing a CMOS battery does not erase your files, photos, or Windows data. What it can affect are BIOS/UEFI settings (like date/time, boot order, fan profile). Many desktops default back to safe settings, but if your PC is older or customized, we want to be careful about boot order so it still starts Windows normally.

Trust moment: I don’t want you to change BIOS settings unless we have to. We’ll confirm the symptoms, then if you proceed, we’ll keep it simple and avoid unnecessary BIOS changes.
Customer
I did the test: I shut it down, turned off the power strip for about 20 minutes, and when I started it, the time was wrong again. So it really is that battery?
Technician avatar Technician
That’s a very strong confirmation. If the clock becomes wrong after a short power cut, the desktop is not holding the hardware clock — and the usual cause is the CMOS/RTC coin-cell battery.

Next, the safest plan is: identify the desktop model if possible (even a photo of the inside label or motherboard brand helps), confirm the likely battery type (often CR2032), and decide whether you want to do a simple battery swap yourself or have someone do it for you. I’m keeping it safe on purpose — I don’t want you prying on clips if you’re not comfortable.

If you tell me the brand/model (or what you see on the startup screen), I can point you to the right manufacturer guide and what to check first so you don’t end up with boot order problems afterward.

Quick answer: what to check first (safe steps)

Accepted fix for a desktop CMOS battery needs replacement situation (safe-first):
• Confirm the pattern: time/date is correct while running, then wrong after the PC is off and wall power is removed.
• Do a short “power-strip test” to verify the clock drops after 10–30 minutes with no AC power.
• Note any startup messages (CMOS battery low / checksum / Press F1 / boot order reset) and the key shown (F1/F2/DEL).
• If replacement is needed, use a model-specific guide, unplug power, and take basic static precautions — avoid touching other components.
• Afterward, set BIOS date/time and confirm the PC still boots from the correct drive (don’t change extra settings).

Common reasons a desktop CMOS battery starts failing

A desktop’s CMOS/RTC battery slowly weakens with age. When it can’t hold the clock, you may see wrong date/time, BIOS reset prompts, “CMOS checksum” warnings, or boot order changes after the PC is unplugged or after a power outage. This often starts suddenly because the battery drops below a usable voltage threshold. The good news is it’s usually a small, straightforward hardware part — but it should be handled safely.

How to tell “Windows time issue” vs “CMOS/RTC battery issue”

If the clock is wrong only after the computer has been off and wall power was removed, it points to the motherboard clock (CMOS/RTC battery). If the time drifts while the PC is running, or the time zone keeps changing, it can be Windows settings, time synchronization, or internet/time server behavior. The simplest confirmation is the short power-strip test: shut down, remove AC power, wait a bit, then boot and check the time. Matching the symptom to the pattern prevents unnecessary repairs.

Desktop CMOS battery replacement — safe troubleshooting tips

Start safe: confirm the pattern, avoid random BIOS changes, and use a brand guide if you open the case.

Safe starting points: keep a note of any startup warning text, take a photo of the BIOS screen if it appears, and avoid changing multiple BIOS settings at once. If you decide to replace the coin-cell battery, unplug the desktop, discharge residual power, and handle parts gently to avoid bending clips or touching other components. After replacement, set the BIOS time/date and confirm the correct boot drive is still selected.

Disclaimer: This information is AI-generated and intended for general guidance only. Do not open the device or attempt unsafe electrical work. For steps tailored to your desktop model and motherboard layout, consult a verified expert or the manufacturer’s support before making changes.

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No guessing, no unnecessary Windows reinstalls. Most desktop “time keeps resetting” cases come down to confirming the pattern and handling the CMOS/RTC battery safely.

FAQ

Why did my desktop start losing time and BIOS settings suddenly?

CMOS/RTC batteries weaken gradually, but the symptoms can appear “all at once” when the voltage drops below a working level. That’s why an older desktop may look fine for years, then suddenly show wrong date/time or BIOS reset prompts. Power outages or switching off a power strip can make it more noticeable. A short power-cut test can confirm it safely.

Could this happen after an update, or is it always hardware?

Windows updates can affect time synchronization, but they usually don’t reset the BIOS clock. If the time becomes wrong only after the PC is off and unplugged, it points to the motherboard clock and battery. If time drifts while Windows is running, it can be settings or sync. The pattern matters more than the timing of an update.

Is it a CMOS battery problem or just Windows date/time settings?

If Windows time is correct during the day but wrong after the PC has no wall power, the CMOS/RTC battery is a likely cause. If the time zone changes or the clock drifts while running, check Windows time settings and synchronization. A safe confirmation is powering down, removing AC power briefly, then checking the time at boot. Avoid changing BIOS options until you confirm which one it is.

Can this be fixed without service if I don’t want to open the desktop?

You can confirm the diagnosis without opening anything by testing whether the clock resets after a short power cut. If replacement is needed and you don’t feel comfortable opening the case, a friend or local shop can do just the battery swap. It’s typically a quick, common repair, but safety matters (unplugged power, static precautions). After replacement, the main “non-service” task is simply setting the correct BIOS time and confirming the boot drive.

Sources

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