How to Know When It’s Time to Replace Your Laptop’s Battery
Windows Will Warn You
Windows doesn’t normally keep you up-to-date with your battery’s capacity level. As you use it and it weakens, you’ll just notice that your laptop doesn’t seem to last as long on battery.
Eventually, when your battery reaches a low enough capacity level, Windows will warn you. You’ll see a red X appear on the standard battery icon in your system tray and, when you click it, Windows will inform you that you should “consider replacing your battery.” Windows also says that your computer might shut down suddenly because there’s a problem with your battery — in other words, your battery can’t hold enough of a charge to power your laptop for long when it’s not connected to an outlet.
Note that this warning was added in Windows 7, so you won’t see it if you’re using Windows Vista or XP.
How to Check Your Laptop’s Battery Capacity
If you’re curious just how far your laptop’s battery capacity has declined, you can use a third-party tool to view it. NirSoft’s free BatteryInfoView does this well, displaying the battery’s approximate wear level, the capacity it was designed to have, and the capacity it currently has.