Why does your computer need a battery?

Computers have a small battery that's important because it keeps the machine's clock running -- and sometimes, your computer. Get the goods on computer batteries in this podcast from HowStuffWorks.com.

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Episode Transcript

Speaker 1 (00:00):
Welcome to Brainstuff from house Stuff Works dot com where
smart happens. Hi am Marcia Brain with today's question, why
does your computer need a battery? Most computers have a
small battery about the size of a nickel. The battery

(00:22):
is usually in some sort of holder that sits on
the motherboard so it's easy to replace. Computers are not
the only things that have a small battery like this.
Camcorders and digital cameras often have them as well. Just
about any gadget that keeps track of time. We'll have
a little battery in your computer as well as these
other gadgets. The battery powers a chip called the real

(00:45):
time clock chip. The real time clock is essentially a
courtz watch that runs all the time whether or not
the computer has power. The battery powers this clock. When
the computer boots up, part of the process is to
query the real time clock chip to get the correct
time and date. A little quartz clock like this might

(01:06):
run for five to seven years off that small battery.
Then it's time to replace the battery. In many cases,
once the battery fails, your computer will no longer boot up.
You would expect the computer to boot fine, but have
an incorrect time and date. The reason your computer will
not boot is because the real time clock chip also

(01:26):
contains sixty four or more bytes of random access memory
known as the se Moss RAM. The clock uses ten
bytes of this space, leaving fifty four bytes for other purposes.
The bios stores all sorts of information in the sims
RAM area, like the number of drives, the hard disc
drive type, and stuff like that. If the sms RAM

(01:49):
loses power, the computer may not know anything about the
hard disc configuration on your machine, and therefore it can't boot.
More modern computers are not quite so dependent on the
Sea Moss RAM. They store their settings in non volatile
RAM that works without any power at all. If the
battery goes dead, the clock fails, but the computer can

(02:09):
still boot using the information in this non volatile RAM area. Then,
once the computer can see the network, you can query
a time server from the network and set the clock
that way. Be sure to check out our new video podcast,
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(02:32):
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