How to Check Your Laptop's Battery Life

I had one of our folks on campus ask about running a diagnostic test to determine battery performance for a laptop. Being the nerd I am, I gave him a bit to chew on. Normally I wouldn't go into so much detail, but he's maintaining a small fleet of laptops so the extra detail could be useful. Figured why not take my novella and put it here...

Often times, you can check a battery condition in the BIOS. This will won't provide a ton of information but it will usually at least provide a basic health factor. If the health of the battery is anything but "Normal" we can safely assume it needs to be replaced. Outside of that, there's not really much in the way of diagnosing the state of a battery. There are a number of tools that will attempt to guess estimated battery life based on how a battery loses charge, but that can be shaky at best. 

Most laptop batteries circa-2000 are lithium-ion based and have a number of cells within them that are charged and depleted. Each cell is somewhat like a human muscle; use it or lose it. If a cell remains completely charged or completely discharged for too long, the cell loses strength and its capacity wains. We're inching our way towards solid-state batteries which may change some things, but that's for another article. Speaking of, here's a pretty short-and-sweet one for maintaining the life and longevity of lithium-ion batteries:

Batteries are 'dumb' so to speak in that there isn't anything in them that examines individual cell performance. The fact that these individual cells can vary in their performance is pretty much why test based on estimated life fall short. A laptop thinks it will last X time based on how some cells are performing and then it gets to weak cells and it only lasts Y in actuality. This is also why battery diagnostic tools can only do so much. But there's another, bigger problem at play.

Your battery performance on a laptop is directly related to how much power the laptop is consuming. The three main contributors to this are screen brightness, cpu (central processing unit, aka your processor), and gpu (graphics processing unit, aka your graphics card). The first is easy to control and settings like screen dim timers, brightness on battery power, blacking out the screen after so many minutes, etc will go a long way to extending the how long a laptop will run on battery. The second two take a little more work to figure out. 

Each process in your computer is using up some amount of CPU and sometimes GPU. This varies greatly from laptop to laptop and user to user. Ever see that person with 50 tabs open on their browser? If they aren't using something like The Great Suspender (which I can't recommend enough for tab junkies) each of those tabs is using up additional processing power. Video games with 3D graphics not only use up a decent chunk of CPU, but more importantly they use up tons of GPU. Then there's seemingly innocuous programs like antivirus, Dropbox or Google Drive, and all that adware you've installed over the years... these all amount to more processes running in the background reducing how long you can expect your laptop to run.

There is a nifty command line tool you can run that will spit out sub-optimal configurations that lead to poorer battery performance as well as any processes that are unusually high. I'd recommend running this on any laptop that is seemingly running poorly. 

In a lab setting, one other thing you can easily do here to rule our poor battery vs poor processing. If you have two same model laptops (one that you know the battery is lasting and one that isn't), swap the battery from the poor laptop to the better laptop, charge it to full and then see how long it lasts. There are some pretty simple but effective programs out there that help you speed up this method of testing by maxing out your cpu and graphics card. This simple one works very well:

It should go without saying, but if you are testing multiple laptops like my user will be doing, be sure to run the test from the same laptop. Even if those laptops are locked down by an administrator, there's entirely too many variables at play between the laptops. If at all possible, run the test from a computer with a fresh OS installed so there are less programs to add to that variability. 

That's if for now, thanks for reading!


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