RTC Battery is Low Fix for Laptops

The other day I was cleaning the fan on a Toshiba laptop, and when I turned the laptop back on, I was met with an error that said “RTC battery is low. Press F2 to set the date and time.” For most people, you can simply tap F2 and the laptop will turn on.

But for me, hitting F2 was challenging because the laptop didn’t have a built-in keyboard and none of my external USB keyboards worked.

What can you do? Here’s what worked for me:

RTC Battery is Low Fix for Laptops:

cmos battery replacement

Your laptop CMOS battery needs to be replaced. Take note of the battery model (either CR2032 0r CR2035) and buy a replacement. Most supermarkets will have these batteries in stock and they cost a couple of dollars.

You can also order CMOS batteries on Amazon. Once you replace the battery, hit F2 on your keyboard and set the date and time, it shouldn’t ask next time you boot. Most CMOS batteries will last for a few years, so it’s a good idea to replace them.

Can’t Press F2:

How do you press F2 if your laptop keyboard is gone? In my case, my laptop’s keyboard was broken, so I removed it and was using the laptop with an external keyboard. Even with the new CMOS battery, the laptop did not recognize the external keyboard.

Here’s what worked for me:

What I did was disconnect the laptop from the power, remove the built-in battery, pop out the CMOS battery, and hold down the power button for 30 seconds. When I put the CMOS battery back in and reconnected the power, the warning still showed but my keyboard was detected and I was able to press F2 to continue.

What is RTC Battery?

RTC stands for Real-Time Clock and it’s powered by a small coin-shaped battery (also called a CMOS battery). The RTC keeps track of your system’s time and date. If the battery on the RTC fails, you will need to manually enter the date and time every time you use the machine.

How to Replace RTC Battery:

The challenging part is finding where on your laptop the RTC battery compartment is located. If you’re lucky, it will be on the small back panel which lets you access the RAM and hard drive. If you’re not lucky, the battery will be buried deep inside the laptop and you’ll have to pry it open.

In most cases, the battery is very noticeable because it’s coin-shaped and usually sits in a black shell on the motherboard. You just need to use something to pop it out and then pop a new one in. It’s very easy.

yellow cmos battery for laptop

Bear in mind, some very old laptops have an RTC battery connected to the motherboard with red and black wires. In that case, you have to buy the same type of battery online, with the same wire and connector. These types of CMOS batteries are harder to replace.

Are CMOS Batteries Rechargeable?

CMOS batteries are not rechargeable. However since the battery only supplies power to the clock, it can last for a very long time. It’s not unusual for CMOS batteries to last for 10 years or more.

Hopefully, that clears up your issue with the RTC battery low warning on your laptop. I hope it helped.

Drop a comment below if you have any questions.


  • Timothy Gagnon is the owner of My Portable Office. As a kid, he's always had a fascination with electronics and never passed on the chance to disassemble and reassemble them. When he's not taking a hammer to his electronics, he can be found playing with his cats or writing about his latest discoveries on My Portable Office.

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