If you have a Windows system, you can do this by going to the Control Panel's Power Options and clicking on Change Advanced Power Settings. After opening the Battery section, adjust the Reserve Battery Level to something lower than 7%.
For Macs, there's no direct equivalent -- but there's an app called Low Battery Saver that can tweak the settings that warn you when your system's running low on battery power and put it to sleep. The app costs $1.99.
8. Smarter outlets
You can also make your outlets more intelligent with a power strip that senses how much current is flowing and shut itself off when a threshold indicates that the system is charged.
9. Don't run what you're not using
It seems obvious, but a lot of people seem to forget this basic principal: If you're not using it, turn it off. In other words, to conserve power, it's best to turn off all nonessential components. I think of it as akin to turning off the lights when I leave a room. For example, when my laptops are not being used, I generally turn off Bluetooth and disable unused ports.
This goes for mobile devices, as well. For example, whenever I'm on a plane, if there isn't a Wi-Fi connection (or if I don't want to pay for it), I keep my device in Airplane mode.
10. Manage your apps
While Microsoft says that unused but live Windows 8 apps don't diminish performance, I still feel strongly that, no matter what OS you're using, it's best to shut down any program that won't be used anytime soon.
11. Clean your machine
Your system is a power waster if it's dirty, so give it a good cleaning every couple of months.
I start by blowing the fan and vents clear of dust bunnies with a can of compressed air. Next, I wipe the battery's terminals down with alcohol pads to clean any built-up gunk that might be robbing the notebook of full battery power. (Unfortunately, many newer systems have the battery sealed inside, preventing this kind of maintenance.)
The power bottom line
I tried some of these power-saving techniques on my trusty old HP EliteBook 2560p: I kept the system from going into Turbo Boost mode, added RAM, installed an SSD, dimmed the screen, adjusted the sleep and display timing, reduced the battery reserve time, turned off Bluetooth and W-Fi and closed older apps when finished using them.
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