Understanding Laptop Battery ratings

Posted By : Ken Colburn of Data Doctors on October 10, 2008 1:38 PM

Question

I want to buy a new laptop, but I've heard horror stories about the batteries that come in lower priced units. How can I tell if a computer that I am considering has a decent battery?

- Gary

Answer

This question was answered on October 10, 2008. Much of the information contained herein may have changed since posting.

One of the most common complaints that I hear from laptop owners is "my battery life stinks"; even from those that have just bought a new unit.

One of the ways that laptop manufacturers reduce the price of a low-end laptop is to put a lower capacity battery in and expect that you will buy an upgraded battery. This allows them to advertise a lower price, with the expectation that they will get you to pay more for a better battery.

One of the first specifications to look for is the number of cells in the battery; the higher the number, the better. If you're looking at a laptop that has a 2, 3 or 4 cell battery, you should budget extra money for an upgraded battery and comparison shop the total against laptops that come with a better battery.

An extra battery can cost from $120 to $250 depending upon the capacity and manufacturer, so be very careful with those low price advertisements.

For most of today's laptops, you should look for a minimum of a 6 cell battery.

The number of cells is not the end of the story, however, because two different 6 cell batteries can have significantly different run times based on another number: the Watt-hour (Wh) rating (the higher the better).

As with most things in the computer business, not all manufacturers publish the specifications for the battery the same way. Some publish the number of cells, while others publish a Watt-hour rating and still others publish neither.

At the end of the day, the Watt-hour rating is the simplest way to determine how much power a battery is capable of storing, so if you can't find a "Wh" rating in any of the specifications, you should remove the battery to see what is printed on it.

If the battery does not have the Wh rating printed on it, it will most likely have a couple of other numbers that you can use to calculate the Wh rating.

Look for the voltage (V) and Amp Hour (Ah or mAh) ratings so you can do the math yourself by multiplying V x Ah. If you see 4800mAh it's the same as 4.8Ah (divide by 1000) which is what you multiply by the voltage.

For example, if you have a battery with the specifications of 14.8V and 4800mAh, you would multiply 14.8 x 4.8 which equals a 71.04 Wh rating.

If you use 25 watts per hour as the average consumption for a laptop, you would expect to get almost 3 hours out of a 71.04 Wh rated battery.

The actual battery life that you will achieve will vary widely based on the exact equipment installed in your laptop and what you do with it.

If you are a hardcore gamer, want to watch DVD movies, listen to music or anything that causes devices to work constantly, your battery life will be significantly shorter than those that spend most of their time creating documents, spreadsheets and e-mails or surfing the Internet.

If you do some simple homework before you make the purchase, you can avoid the all-too-common "battery surprise" that many others are suffering!

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Posted by Ken Colburn of Data Doctors on October 10, 2008

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