Battery Technology - Laptop Batteries Life
them. This is rated in mAh or milliampere-hours.
I could go into technical details but suffice to say,
the higher the mAh that a battery is rated out, the
more energy that is stored in the battery.
So, why is the battery capacity important? Of two
systems that use the same amount of power, the one
with a higher mAh rated battery will last longer. This
makes comparison easy for the batteries themselves.
The problem is that no two laptop configurations
will draw the same amount of power.
Power consumption of a laptop depends upon all
You have seen the claims by manufacturers that
of the components that make up the system. So, a
their laptop will run five, six and even eight hours
system with a lower power consumption CPU will
on a single charge. These sound like spectacular feats
generally last longer if all parts are equal but they
that would actually allow one to use a laptop for an
almost never are. It gets even more complicated
entire flight across the continental United States. The
because the power consumption can also vary de-
problem is that most of these laptops would not be
pending upon how the laptop is being used. Heavy
able to run for that long. How can manufacturers
disk uses draws more power than little usage.
make such claims about their laptops even though
no users are able to achieve such results?
All isn't lost for consumers though. In general the
size of the laptop will also equate to how much power
This article will look into what aspects of a laptop
it uses. For example, a desktop replacement will
determine how long it can run on a fully charged
generally draw more power than a thin and light.
battery, how manufacturers achieve such high num-
A thin and light draws more power than an ultra-
bers and how I test laptops for real world battery.
portable and a netbook draws even less still.
Hopefully this can help users to get a better idea of
what to expect when it comes to how long they can
expect a laptop to actually run when not plugged in.
Battery Capacity and Power Consumption
There are to things that will be the basis for de-
joli termining how long a laptop computer should run
Now that the basics are out of the way, how can a
on batteries. Of course, the overall capacity of the
manufacturer come up with a claim of something
battery is the easiest to determine and understand.
like ten hours of running time for a laptop yet a
All batteries can store a fixed amount of energy in
user in real world use may get only half as much
Battery Technology - Laptop Batteries Life Lies
time? It all has to do with how the manufacturers
How I Test
conduct their battery life tests. The most common
of these is a function of the MobileMark benchmar-
king suite from BapCo. It simulates computer usage
through sampled application use via programs such
as Quicktime, Photoshop, Flash, Office and WinZip.
Now, this is a valid test that simulates usage, but it
is how the test simulates usage. The test generally
has the CPU idle during much of the test on the basis
that many people are either idle or their applications
are awaiting user input. It also doesn't set various
power settings within the OS. Manufacturers often
use various tricks such as decreasing the display
brightness to the lowest levels and turning all of
the battery saving features to their maximum the
Here at the About.com PC Hardware / Reviews site,
running time so they can get the highest run times
I do not use the MobileMark application or the va-
rious tricks that the manufacturers may use to get
their various numbers for advertising. Instead, I use
The problem is that this is not how people use their
a video playback test on all laptops and using the
laptops in real life. A good example is people who
default power profiles and software settings that
use their laptops for viewing DVDs on an airplane
a laptop ships with. For laptops with a DVD com-
flight. This is one of the more consistent battery
patible drive, this entails playing back a standard
drawing tasks that one can use on their laptop. Thus,
DVD movie in a loop until the system shuts down.
a battery life claim of four hours might net just two
On laptops without a DVD drive, in entails playing
hours of DVD viewing.
back a Quicktime based video loop until the system
shuts down. This in my opinion gives some of the
best real world usage numbers available.
In general, these tasks are some of the toughest when
it comes to power consumption. Typically, such a
test will result in anywhere from 50 to 75% of the
manufacturers claim of battery life. Of course, this
is just one method of testing. People use their lap-
tops in various ways and will generally get more
battery life than this type of test but still below the
Battery Technology - Laptop Batteries Life Lies
What Consumers Should Do With Battery
Any consumer who is presented by a battery life
number from any company or sales person needs
to take this number and modify it to get a better
idea of just how much battery life they would get. To
determine this, you should really consider whether
you use your computer heavily or lightly. A heavy
user is someone that runs applications such as
video editing, PC gaming or a large number of si-
multaneous applications. Light users are ones that
typically only have one or two applications open at
a time, use it primarily to browse the web or use
Once you have determined the type of user you are,
it is best to half the number if you are heavy users
and subtract about one quarter if you are light user.
For example, a four hour battery life claim will net
roughly two hours of use for a heavy uses and about
three hours from a light user. This is just an estimate
because it is very difficult to determine how long a
battery will run on a laptop until it is used in your
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