Can CMOS battery be changed early without messing up BIOS?

MisterEd said:

Once you remove the battery any previous settings will be lost. If you didn't make any changes then that should be no problem. Taking pictures of the BIOS screen is good insurance in case there any important settings that need to be set again.

BTW, I make very very few changes in the BIOS settings so I have no problem with this. I have lost track of how many times I had to replace a BIOS battery. Some were even after the original battery was dead.

I haven't made any BIOS changes, so it sounds like I wouldn't have much to do after all. That's great to know. I've always heard that resetting BIOS after a CMOS failure was a big headache. I guess most people make changes, and that's probably why it ends up being so difficult after a failure.

Megahertz said:

BIOS battery can last for more than five years. If the date and time isn't changed after a long period with the computer off the battery is still good.
Desktops has more BIOS options so it is more tetchy to set
On a Laptop there is almost nothing to set other than date and time.

Mine is a laptop, so that's good news for me.

Ghot said:

You absolutely can not move faster than electricity. ^^

Even Bruce Lee or Superman could not move faster than electricity.
Electricity is much, much, much faster than... a speeding bullet.

I have a thermostat in my house that runs on 2AA batteries and I found that the display stays on and settings are maintained for around 10 seconds after I remove the batteries. When I do a battery change for it, I try to put in the new batteries within 10 seconds so as not to lose the thermostat's settings. I thought maybe the CMOS battery in my laptop might work similarly.

Bree said:

Hmm, my oldest laptop dates back to 2009 and I have several more that are nearly as old. I've never had to change a CMOS battery on any of my laptops.

Interesting!
I just did a Google search for how long a CMOS battery lasts and came up with all kinds of answers. 2-10 years, 3-5 years, one that said up to 20 years.
And then I found on hp.com what doesn't sound right at all. They claim the CMOS battery gets recharged when the computer is plugged in. Uh, no it doesn't. Even I know that! Here is what they said: "The CMOS battery gets charged whenever your laptop is plugged in. It’s only when your laptop is unplugged that the battery loses charge. Most batteries will last 2 to 10 years from the date they’re manufactured. The more you leave your laptop plugged in, the longer your battery will last."

Ghot said:

There's probably a capacitor in the thermostat circuit somewhere that holds a charge, briefly.

You can NOT beat electricity, it's much too fast.



Pulling the CMOS battery is one of the ways we reset the BIOS to defaults.

Ok, well I guess I won't do a pre-mature CMOS change after all. I thought maybe I'd do it to prevent any headaches in the future when it dies unexpectedly, but I guess I'd just be creating an earlier headache, unless it's true that the defaults would be there and all I'd have to do is reset the clock.

Ghot said:

Some laptops, don't let you access hardly any BIOS settings, some let you access a lot.
They should all let you access the time/date.

So... whether you pull the CMOS battery or not, shouldn't really make much difference.

As someone mentioned above... just take pics of whatever settings you DO have in the BIOS, as a fall back.

Will do.
And I think I'll wait on changing the CMOS battery. Changing it now wouldn't serve a purpose at this point.

Hello,

If the laptop you're asking about is the same one listed in your system specs here, Dell Inspiron 15 5558 (Release date June 2015). Then replacing the CMOS battery is simple. Be sure to leave the CMOS battery out for 10 seconds to ensure the BIOS settings go back to its factory default. Once the battery has been replaced go to Dell website, link provided below and click on 'check for updates'. Dell will automatically scan your system and provide a list of drivers, and BIOS to install. Note: Before replacing the CMOS battery, you can check your current BIOS version by Pressing the Windows key + R. Type “msinfo32” into the Run box. Hit Enter. Check the BIOS version number under System Summary. See the “BIOS Version/Date”.

https://www.dell.com/support/home/en...laptop/drivers

https://www.youtube.com/watch?v=D9W-...ople.com%2CInc

MisterEd said:

PCs have been been using the CR2032 non-rechargeable battery for decades now. It has the advantage of being easily found for purchase. If you need one you can just run down to Walmart to buy one.

My Raspberry Pi 5 does have a rechargeable RTC battery. If I need another one I will have to order another one online and wait a week to get it. The Raspberry Pi doesn't need the battery to save any settings. Normally the Raspberry Pi goes online to set its internal clock. It uses the battery to keep the clock running and set even when the Raspberry Pin does not go online.



Raspberry Pi - RTC Battery for Pi 5 - SC1163: This rechargeable lithium battery is designed to be used with Raspberry Pi 5 to power the onboard real-time clock (RTC) whenever mains power is disconnected.

I just had my Lenovo laptop open and saw the CMOS battery in it and it looked much like the one in your picture. Makes me think it's rechargeable as well.
The one in my Dell is the regular 2032 AmericanPharaoh showed in the Youtube video (post #18). That's the one that's 7 years old.

To American Pharaoh: If I wanted to maintain my BIOS settings as they are now, should I not wait those 10 seconds before inserting the new battery? (This of course would mean changing the battery early rather than waiting for the current one to die).

As I have understood it, the CMOS battery is only used to keep the Real Time Clock running, when the main battery is disconnected or completely discharged.