If you receive an error while booting that indicates your CMOS (complementary metal-oxide semiconductor) battery failed, or if you notice that your real-time clock is consistently losing time, you might have a failing or dead battery. Contact your motherboard supplier (or the motherboard manufacturer) for information about receiving and installing a new battery, or simply find a replacement and install it yourself. Some batteries are soldered onto the motherboards, so you may want to let a tech shop replace those. Other batteries are just held in place by a clip; and those are the ones that you can replace on your own. You can buy replacements online or at a computer store, but you must order the right type of battery for your motherboard. The motherboard manufacturer should be able to provide information as to an appropriate battery for the board, but may require a phone call or email. Some dead batteries may include specifications directly on the battery as well (specifically the flat batteries).


Make and model information should be stamped on the motherboard. It should also be listed in teh BIOS information, which is accessible by pressing and holding down a key (often the DELETE, ESC, F1, or F2 key) when the computer begins booting (or repeatedly pressing the key). (The BIOS information that appears on-screen when you turn on the PC will indicate which key your system requires you to push.) In a moment, you’ll see the main menu of the BIOS setup utility. You’ll probably have to use the keyboard to navigate its options. Motherboard information listed in the BIOS may appear as a long string of characters, such as 51-0102-zz1526-00111111-101094-AMIS123-P

Answer:
To install a new battery yourself, turn off your computer, ground yourself by touching something metal outside of the computer case, open the case, and locate the battery (see image below). Remove the old battery from beneath the clip and insert the new battery. Replace the case cover and start your computer. ( NOTE: Not all motherboards permit replacement of the CMOS battery, so check your motherboard’s manual for more details.)