How Long Does the 3V Motherboard Battery Last?

You might ask "What is the 3V motherboard battery"? On the majority of PCs the motherboard holds a +3 Volt Lithium Battery which is used for two functions. Firstly it keeps the computer time updated. Secondly, on older PC's it keeps the BIOS settings (Low level start-up instructions) in memory.

By the way, on most modern PC's the time is updated from the web. The 3V battery just keeps the time when the PC is powered off. This is useful as the motherboard clock is not very accurate, easily losing a couple of minutes per day.

If you have your PC case off you will see something on the motherboard that looks like a small thick silver coin. That is the battery. There are other types of battery used on newer machines (Ni-Cad, NVRAM) but these much less frequently found and so I will not discuss them further.

So how long does it last? Anything from 3 to 9 years if you search this question on Google. Everyone has a different opinion. In my experience about 6 years is the average. It's basically a large watch battery and is constantly supplying a trickle of power to the motherboard. Just like many of my watches the battery can last 2 years or up to 6 years (Fossil watches do not seem to last long for me for some reason). How long was the PC in the warehouse before it was delivered? And, how long was the motherboard in the warehouse before it was installed in the PC?

Why is this important? If you have a reliably new PC the only problem you will get are error messages relating to the clock on start up. No big deal. If your PC is older then a low battery could be a nightmare. I had a PC which once every few months refused to boot. Rather than take the PC in for repair or start replacing parts myself the first thing I did was look at the BIOS settings. It was soon obvious that the BIOS settings were corrupt (wrong bus speed). I put a volt meter on the battery and sure enough it was reading 2.2 volts.

I could easily have spent a fortune replacing the motherboard, the memory, the processor etc when it all came down to 2 dollar battery. What's more are these batteries are easy to get. What you need is a CR2032 available at most hardware stores like home depot and I've even seen them sold in Safeways. Of course every reputable computer store should stock them. Just check to make sure that your PC uses a CR2032 before you go to the shops!

I run a PC repair business in Vancouver. I always tell people who call with clock problems to check their motherboard battery first before calling me round. For most people it's easy to check and easy to replace. I do not want to make money from fixing something so simple.

So how do you replace it? In most cases very easily. It should be easily removed with some tweezers, just be careful not to short circuit the + (top) and – (bottom). Also be careful not to over stress the clamp that holds it in place. After you have replaced the battery the BIOS settings will be set to default. This means that if you had any special settings (boot sequence, overclocking etc) you would have to go into the BIOS (usually F2 or DEL whilst booting) and reset them. This is a good opportunity to reset the time and date also. Use the arrow keys and return to change these settings.

So, in summary, if you have a PC which is showing clock errors or BIOS problems look first at the little 3 volt battery. It could save you a fortune. Happy computing!

Source by Rory Cain


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