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Laptop Battery Life Lies

Why Manufacturer Laptop Battery Life Claims Never Equal Real World Running Times

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You have seen the claims by manufacturers that their laptop will run five, six and even eight hours on a single charge. These sound like spectacular feats that would actually allow one to use a laptop for an entire flight across the continental United States. The problem is that most of these laptops would not be able to run for that long. How can manufacturers make such claims about their laptops even though no users are able to achieve such results?

This article will look into what aspects of a laptop determine how long it can run on a fully charged battery, how manufacturers achieve such high numbers and how I test laptops for real world battery. 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 determining how long a laptop computer should run on batteries. Of course, the overall capacity of the battery is the easiest to determine and understand. All batteries can store a fixed amount of energy in 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 of the components that make up the system. So, a system with a lower power consumption CPU will generally last longer if all parts are equal but they almost never are. It gets even more complicated because the power consumption can also vary depending upon how the laptop is being used. Heavy disk uses draws more power than little usage.

All isn't lost for consumers though. In general the size of the laptop will also equate to how much power it uses. For example, a desktop replacement will generally draw more power than a thin and light. A thin and light draws more power than an ultraportable and a netbook draws even less still.

Manufacturer Claims

Now that the basics are out of the way, how can a manufacturer come up with a claim of something like ten hours of running time for a laptop yet a user in real world use may get only half as much time? It all has to do with how the manufacturers conduct their battery life tests. The most common of these is a function of the MobileMark benchmarking 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 running time so they can get the highest run times possible.

The problem is that this is not how people use their laptops in real life. A good example is people who use their laptops for viewing DVDs on an airplane flight. This is one of the more consistent battery drawing tasks that one can use on their laptop. Thus, a battery life claim of four hours might net just two hours of DVD viewing.

How I Test

Here at the About.com PC Hardware / Reviews site, I do not use the MobileMark application or the various tricks that the manufacturers may use to get their various numbers for advertising. Instead, I use a video playback test on all laptops and using the default power profiles and software settings that a laptop ships with. For laptops with a DVD compatible drive, this entails playing back a standard DVD movie in a loop until the system shuts down. On laptops without a DVD drive, in entails playing 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 laptops in various ways and will generally get more battery life than this type of test but still below the manufacturer numbers.

What Consumers Should Do With Battery Life Numbers

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 simultaneous 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 productivity software.

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 typical fashion.

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