Dead System Battery = No Boot?

Started 4 months ago | Questions
SantaFeBill Veteran Member • Posts: 3,141
Dead System Battery = No Boot?

I'm getting a warning that the voltage in my system's battery is low. (The battery is very old - I'm sure the warning is correct.)

I read somewhere that if the system battery dies, the computer will no longer boot. (PC, Windows, desktop, connected to an UPS).

Is that correct?

Thanks to all.

ANSWER:
Sean Nelson
Sean Nelson Forum Pro • Posts: 14,865
Re: Dead System Battery = No Boot?
2

SantaFeBill wrote:

I read somewhere that if the system battery dies, the computer will no longer boot. (PC, Windows, desktop, connected to an UPS).

There once was a time when important information needed to boot the system (such as the number of cylinders, sectors per cylinder, etc. of pre-IDE hard disks) was stored in a volatile RAM chip whose contents were maintained by the system battery. If the battery died then the information was lost and had to be re-entered through the BIOS in order to boot the system. The system wasn't "unbootable", it was just no longer automatic because it would stop and ask for the time and BIOS configuration.

These days that information is all stored in nonvolatile flash memory and the only thing the system battery is really used for is to maintain the wall clock time. So it's hard for me to imagine why a modern motherboard wouldn't be able to boot. It might still stop to ask for the time, though.   But since the system will normally get the time from the network once it's up and running even the time is no longer all that essential.

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tkbslc Forum Pro • Posts: 16,660
Re: Dead System Battery = No Boot?
1

SantaFeBill wrote:

I'm getting a warning that the voltage in my system's battery is low. (The battery is very old - I'm sure the warning is correct.)

I read somewhere that if the system battery dies, the computer will no longer boot. (PC, Windows, desktop, connected to an UPS).

Is that correct?

Thanks to all.

As was said, it will likely just lose the date and time.

But, typically these are just watch batteries on the motherboard (CR2032). So it should be cheap and easy for you to replace.  Can pick one up at the grocery store, even.

OP SantaFeBill Veteran Member • Posts: 3,141
Re: Dead System Battery = No Boot?

Thanks, Sean. Very helpful.

SC489 Senior Member • Posts: 1,441
Re: Dead System Battery = No Boot?
2

SantaFeBill wrote:

I'm getting a warning that the voltage in my system's battery is low. (The battery is very old - I'm sure the warning is correct.)

I read somewhere that if the system battery dies, the computer will no longer boot. (PC, Windows, desktop, connected to an UPS).

Is that correct?

Thanks to all.

You are lucky to get a warning. My 2012 Gigabyte motherboard suddenly fails to boot and is dead if the CMOS battery voltage drops to 2.8V. This happens about every 2 years since the PC is off at the mains much of the time and relies on the battery to save the BIOS values. The problem is easily sorted by replacing the CMOS battery. Fortunately my motherboard saves BIOS settings and I can easily recover my preferred settings.

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SC489 Senior Member • Posts: 1,441
Re: Dead System Battery = No Boot?

Sean Nelson wrote:

SantaFeBill wrote:

I read somewhere that if the system battery dies, the computer will no longer boot. (PC, Windows, desktop, connected to an UPS).

There once was a time when important information needed to boot the system (such as the number of cylinders, sectors per cylinder, etc. of pre-IDE hard disks) was stored in a volatile RAM chip whose contents were maintained by the system battery. If the battery died then the information was lost and had to be re-entered through the BIOS in order to boot the system. The system wasn't "unbootable", it was just no longer automatic because it would stop and ask for the time and BIOS configuration.

These days that information is all stored in nonvolatile flash memory and the only thing the system battery is really used for is to maintain the wall clock time. So it's hard for me to imagine why a modern motherboard wouldn't be able to boot. It might still stop to ask for the time, though. But since the system will normally get the time from the network once it's up and running even the time is no longer all that essential.

That isn't true - see my other post.

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keith Contributing Member • Posts: 515
Re: Dead System Battery = No Boot?

What can happen is that the bios defaults to IDE for the way it handles disks.  If you have set up ACHD , the system will not boot if the BIOS sets to IDE when the battery fails or you remove it to change it.

Keith

Robert Zanatta Senior Member • Posts: 2,154
Re: Dead System Battery = No Boot?

Depends on your motherboard.  BIOS settings may be stored in volatile memory on older and some newer motherboards.

Just replace the battery.  You may lose your BIOS settings after doing so and require reconfiguring.

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Eric Carlson
Eric Carlson Veteran Member • Posts: 6,973
Re: Dead System Battery = No Boot?
1

SantaFeBill wrote:

I'm getting a warning that the voltage in my system's battery is low. (The battery is very old - I'm sure the warning is correct.)

I read somewhere that if the system battery dies, the computer will no longer boot. (PC, Windows, desktop, connected to an UPS).

Is that correct?

Thanks to all.

You usually don't lose settings, but you sometimes do. I usually get 10 years out of CMOS batteries, sometimes only 5. I bought a bunch, I think via Amazon, for really old PC's and other things.

Just in case, you might want to take a photo of all your BIOS settings screens, and make sure those photos aren't only stored on that same computer. And sometimes a full reset, then putting back in the settings is helpful.

PS: And if you're doing all that, make sure you have the latest BIOS installed.

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OP SantaFeBill Veteran Member • Posts: 3,141
Re: Dead System Battery = No Boot?
1

Thanks. Taking a photo of the Bios settings is a great idea.

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