CMOS battery, also known as a ‘clock battery’ provides the main power source for the motherboard of your computer. It is called CMOS battery because it stores settings in CMOS so you see the correct time when the computer takes its settings from system memory. Without a functioning CMOS battery , your computer will not boot up or keep proper time.

How long does a CMOS battery last?

A typical battery life is between 5 and 10 years, but it depends on factors like temperature, discharge rate and usage. Manufacturers usually specify how long the CMOS battery should remain in the computer depending on the coin cell used inside. For example, manufacturers of the CR2032 state that this battery should last up to 6 years as a CMOS battery.

How do I choose the correct CMOS battery?

Computer manufacturers provide information about replacement batteries in the following places:

  1. On the battery itself: Look for a battery part number or an FRU printed as well as the type of battery. For example, the battery pictured below has an FRU part number 04X0443 and it is a CR2016 battery.
  2. In the user manual: If replacement battery is not listed anywhere else, you can check if there’s information about CMOS batteries or a PDF manual.
  3. Contact support: Manufacturer’s support will be able to tell you the part # of the CMOS battery from their internal database.
  4. Contact support: CMOS batteries can be cross-compatible between multiple computers and we maintain a comprehensive up to date database.



What if I can’t find any information?

A CMOS battery has five components: connector, polarity, leads, length and battery type.

Connector: Computer manufacturers use different types of connectors depending on the motherboard design and specifications. Connectors are not cross-compatible  with each other and oftentimes look very similar. Some connectors have two pins and some have three.


REG NP Front CloseupLONG PN Front CloseupSLIM NNP Front CloseupREG PEN Front Closeup

Polarity: All CMOS batteries have a positive or negative polarity. If the + (red) and – (black or white) signs are not lined up properly on the connector, the battery will not work. Most of the time, you can tell which is positive and negative just by looking at the color.

Pos Neg

Leads: CMOS batteries typically have two or three leads coming from the coin cell battery to the connector. Some batteries have three pins, but only two leads.

Length: Leads can be short, medium, long or extra long. It’s best to measure the leads in centimeters (cm) and get a replacement that is the same or a little longer. You can always tuck away extra few centimeters near the battery slot.

S 03 1S 09 1 1

Battery type: Most newer computers have a lithium-ion CR2032 coin cell battery, but some older computers have a Ni-MH or Ni-Cd battery which is harder to find.

1 31

Battery size: There are several choices of coin cell batteries based on the physical aspect, such as diameter and thickness of the battery . These dimensions can also be found from your motherboard documentation or locate it on the battery itself. If the battery is wrapped in PVC film, you can carefully peel away the film and see the type of battery underneath. PVC film is used to shield batteries and prevent electrical interference.

CMOS Battery 2032

With all of this information, you can build your own battery by using an Easy CMOS Battery Builder located here.

How to build your own CMOS battery?

  1. In Step 1: Start by matching your connector to one of the available connectors in the builder. In this step, we are only choosing a connector and ignoring polarity or number of leads.
  2. In Step 2: Choose the polarity. Align your computer’s CMOS battery in the same exact way and match up the + (red) and – (black or white) colored leads.
  3. In Step 3: Choose the length of the leads that is the same or longer than the original OEM CMOS battery.
  4. In Step 4: Choose the battery type. Battery type must be an exact match. All of the lithium-ion coin cell batteries have a 3V output, but vary in size and thickness.

What if my battery type is not available?

Contact and get your custom battery manufactured. There is no surcharge for custom batteries, but manufacturing time can be about 30 days.

In conclusion,  be sure to choose an exact replacement battery for your motherboard. If you are unsure about what type of CMOS battery is used or have any other questions, contact and we will be happy to help you with your custom made battery needs.

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