Weak CMOS Battery May Prevent Your Computer from Booting!

[Fly Guy]

For the last two years I couldn't figure out why my three year old computer wouldn't boot. It wouldn't turn on after a power outage. And even if I did properly shut down the computer the night before, it still wouldn't turn on the next morning. I would have to drain the computer by disconnecting the PSU. At first it was a few minutes, then it gradually took a whole day for the computer to drain, then only would the computer boot up. What confused me was the computer worked like a champ when the computer decided to power on.

Then just last week my computer acted even more strange than what I've described above. The computer would power up after pressing the power button but then it would immediately shut down after two seconds. I looked online and the comments were mostly, "The culprit is most likely the PSU. You need to test your computer with another PSU."

Another person with similar computer issues like me jumped through loops with the advice they gave him online, e.g. re-seat hardware, install another PSU, etc. None worked so he decided to change CMOS battery. The computer then worked like a champ again and has no problem booting. And so did this too work for me. No costly unnecessry PSU, CPU, RAM, MOBO replacement.

Anyone has any theories as to why a weak CMOS battery would prevent the computer from booting and shutting down mid way before a complete boot? It's ridiculous. You will not find this advice on the web that the CMOS battery could be the culprit because as they explain, "The purpose of the CMOS battery is to only hold date and time. A dead or weak CMOS battery will not prevent the computer from booting. You'll just lose date and time."

[Bad 💀 Motha]

Motherboard have been this way for MANY years; why is this news to folks?

If a motherboard has a serious boot issue, then first thing to check is CMOS Battery Voltage.
If drops below around 2.7-8x volts, then it's dying. It is a 3V battery.
However they should last approx 3 - 5 years, easy.

You can buy these batteries (CR2032) in a multi or otherwise low count bulk for very cheap online. Like (5x for $3 / 15x for $7) on Amazon for example.

You can store such batteries for quite a # of years if un-used; just like other batteries people tend to buy in bulk.

And please know many Laptops are the same way; they typically use the same model of battery as well; but most laptops have that battery shrink-wrapped and then connect to the motherboard via a custom 2pin connector; however you can also replace that yourself, with little work.

[timetripper]

I have the EXACT problem with an Inspiron 7527. It went into a perpetual restart (screen blank, keyboard lights, HDD whirs, shuts down, repeat.)

Replace the CMOS and it worked - for three days. Then, same problem.
Replace the CMOS, it boots, upgrade the BIOS, it works - for five days.
Today, same problem.
If it's the MB, I don't see how it could work so robustly for days.
Any thoughts?

[[☥] - CJ -]

dunno..
Only time i ever had such issues were back on a DDR2 system and caused by a DIMM slot/RAM stick

[Gatuno]

I know it really really really really really old, but I just had some trouble with my Dell Inspiron 15 5547

It CMOS Battery just completly died preventing it to boot up (not even POST). Everytime I tried to turn it on, I got a 5 Beeps error from it, and going to Dell's Beep Error codes table, 5 Beeps means problem with RTC (Real Time Clock) which leads to weak/dead CMOS Battery. Today I sent it to a friend so he could tear it up and change it battery to send me back so I can test.

And there we go, the Laptop is working as if nothing happened.

Just like Bad_Motha said, some new Motherboards will prevent any boot while your CMOS Battery is dead or in very low voltage.

So if you ever encounter this problem with your laptop or PC not booting up all of suddenly, you might want to check it CMOS battery to see if it not dead/low voltage.

Cheers guys.

[Bad 💀 Motha]

Yes, when you own PCs, buy some extra CR2032 batteries in bulk. Even Energizer is cheap in bulk on places like Amazon. They have like 10 years shelf life; then when u need to replace one, u'll have it.

[viperwolf02]

Mine was my ssd started to go bad. I have not had the problem sense I replaced it.

[MOOSEYT 🏄]

worked for me, thanks brother mobo is asus b250f

[Jon Umber]

I'm having exactly the problem you described!!! To a tee, even how it acts after clearing CMOS. I have an Asus Sabertooth Z97 Mark 1 from 2014.

I've unplugged and reseated everything, tested every stick of RAM, cleaned everything, updated BIOS. I'm about to take it to a PC shop but stumbled on this post and about to try replacing my CMOS battery. I was starting to think I'd have to replace my motherboard or PSU.

If this works I'll name a child after you, OP.

Edit: Unfortunately my problem was worse than this. Mobo died.

[pasa]

My battery is dead for years -- will replace it next time I have to open the box for some other reason.

The only effect I see is that after a power outage the cmos content is lost. So it must be re-created. With special attention to the secure boot OS type or what, that will indeed halt booting to W7 unless set to "other" from the default.

[wajinshu]

This is true. Experienced it today, almost gave up and disassemble my GPU, Ram and HDD/SSD. Then when I removing my NVME drive I seen the CMOS battery and removed it then it was booting up with light. Didn't problems with this before in my last 3 computers.

Problem started when I just shutdown my PC, drink some water downstairs and when I back to my PC it's not responding with the power button. Tried different PSU as well. I'm using the same battery as of now.

So close to RMA the board. So guys try to remove the CMOS first if there's Boot problems.

[DRIFTER]

I have also this problem. Notebook lenovo Z50-70 - 5years old. I tried external monitor, clean RAM, change RAM port, HDD is working, disconnect keyboard, USB port...to be sure there is no short-circuit...Finally I tried to heat up some areas with heat gun...and? Laptop woke up. And gone 2-3-5 hours without any problems. But when I restarted or shot down I faced the same problem. By my opinion heating up gave battery "energy" for loading BIOS, after this CMOS battery cold down, lost voltage and problem repeats. So I am going to replace CMOS battery and hope I will solve this problem. I will let you know.

[imcalfin]

I just managed to solve my issue by simply replacing the CMOS battery. Computer would not power up at all, no fans spinning, no nothing - graphics card's and USB disk's status LEDs did light up, so clearly there was power somewhere to be had.

The motherboard in question: Gigabyte H87M-D3H

So yeah, some MoBo's apparently refuse to do anything at all if the battery is dead. Mine never gave any of the usual signs (dates going wonky etc.). The issue came up after I came back from a trip - maybe the nine days of being disconnected from mains managed to kill the batt for good? Being connected to power overnight, or changing the PSU, didn't help (both PSU's did pass the pin test so they weren't the likely culprit anyway).

At least I finally got around to cleaning the computer, though. So not a total bummer.

TL;DR If your comp does absolutely nothing at all and you've exhausted the obvious silly reasons (ie. power cord connected) - try chaning the CMOS battery. Like someone said, they're cheap, easily available (mine were lying around because I have a scale that uses them) and fairly easy to replace in most desktop comps.

[Nabster]

I better try this myself, my computer has been acting up

[Tiberius]

Doesnt this kind of problem show up in Mobo postcode? I always buy a mobo that has its own postcode to anticipate this kind of problem

[Gatuno]

Tiberius původně napsal:

Doesnt this kind of problem show up in Mobo postcode? I always buy a mobo that has its own postcode to anticipate this kind of problem

traditionally, many mobos use buzzers that scream certain numbers of sequentials "beeps" to the user, and by looking at a beep table provided by the manufacturer, the user can see what error is being issued.