How to measure battery life before buying a laptop

How to measure battery life before buying a laptop
How to measure battery life before buying a laptop

Laptop manufacturers brag about their battery life by saying that it works for more than 12 hours on a single charge, but after bringing the laptop home, it is very difficult to keep it for three hours.  These things are completely different from our practice than the determinations made under special conditions.  Therefore, if we can make an accurate guess based on our usage instead of fairy tales told by advertisements, manufacturer websites, and sales assistants in shops, it will be easy to decide on a purchase.

 An equation for battery life

These calculations are much easier than Rosa’s physics annotations to cut the number period.  No matter what the marketers say, they can’t hide the battery life numbers.  Therefore, they can be used for our precise calculations.

 First, you need to find the battery capacity or watt-hours.  This is expressed in units of Wh or Whr.  A laptop consumes 10-15 watts in normal use.  For example, a laptop computer with a 100Wh battery can be used for 7-10 hours in normal use, and when the 100Wh value is divided by 15 and 10 watts, the value of 7 to 10 hours is obtained.

 This value can be considered as the continuous usage time of the computer and at the end of charging, a voltage change or some manufacturing companies shut down the computer to maintain battery power for the time it takes to sleep or hibernate.  This should be taken into account.  Accordingly, the equation is:

 Wh value of the battery / estimated wattage = battery life in hours

 By flipping this around, i.e. if you want to choose a laptop with the desired battery life, multiply those hours by the estimated wattage to find the Wh value of the laptop battery to buy.

 Finding the Wh value

Finding the Wh value of the laptop is very easy.  For this, do a Google search using the computer’s model number or the product code made up of numbers and letters.  Then you can check the specifications from the manufacturer’s website.  For Apple computers, you can see all other technical data, including the battery, from the link mentioned above as Tech Specs on the website.  Or if you see the laptop in the store, ask for its power adapter and check it.  Most have these values ​​listed on the underside of the adapter (the big black brick).

 The number of battery cells in these specifications is not relevant to our calculations.  If the mAh (milliampere-hour) values ​​are indicated and the V (volt) value is mentioned along with it, we can set the Wh value by multiplying the two values ​​and dividing by 1000.  The easiest way to do this is to use an online calculator.  If these values ​​cannot be found on the adapter or on a website and if the sales assistants bother you, turn on the computer if Windows is already installed on it, type cmd in the command box via the Windows Key + R shortcut and open the command prompt.  When you type powercfg /battery report and enter, you can see the battery details.  In addition, if possible, by removing the battery, you can see that this information is printed on it or where the battery is installed.

 Estimation of wattage

The wattage of the computer or the number of watts it uses (capacity or the amount of energy used per second) is determined by the amount of work we do through the computer.  If you open software like Photoshop and Illustrator at the same time and do a large-scale graphic design on a computer that is for sale for about 10 hours, the battery power can reach a low value in about three hours.

 Use the following data to estimate the wattage.

  •  60 and above: Heavy computer games, video processing activities
  • 40-60W: Normal-sized PC games
  • 30-40W: Video or photo editing work
  • 20-30W: Watching HD videos online
  • 15-20W: Watching an HD video on the computer or using several programs at the same time
  • 10-15W: Browsing the Internet, Word, or listening to music with a normal amount of tabs
  • 8-10W: Minimum power at which the screen is active


Often, 10-15W can be considered as normal usage and you should think about the higher values ​​mentioned here if you have the habit of opening or forgetting to close several programs at the same time, if you buy a computer with an additional graphics card (those available as Intel graphics).  No), if the screen brightness is used at a high value if devices such as phones are continuously connected to charge, only if the screen size is more than 15 inches.

 So now you can make the most suitable choice as an expert in finding the battery life that suits your work instead of the battery power that is told through marketing tactics.  These calculations will be important to consider not only when buying a new laptop, but also when buying a new battery if you have to replace the battery of the same laptop.

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