It isn't possible to overcharge a laptop battery. Leaving your computer plugged in after it is fully charged doesn't overcharge or damage the battery. However, it is possible to take steps to optimize the battery life of your laptop.
Most modern laptops use Lithium-ion batteries. These batteries can be charged hundreds of times without affecting the battery life. They have an internal circuit that stops the charging process when the battery is fully charged.
The circuit is necessary because without it the Li-ion battery could overheat and possibly burn as it charges. A Lithium-ion battery shouldn't get warm while it is in the charger. If it does, remove it. The battery may be defective.
Nickel-Cadmium and Nickel Metal Hydride Batteries
Older laptops use Nickel-cadmium and Nickel metal hydride batteries. These batteries require more maintenance than Lithium-ion batteries. NiCad and NiMH batteries must be fully discharged and then fully recharged once a month for optimal battery life. Leaving them plugged in after they are fully charged doesn't affect the battery life appreciably.
Mac Notebook Batteries
Apple's MacBook, MacBook Air, and MacBook Pro come with non-replaceable lithium polymer batteries to provide maximum battery life in a compact space. To check the health of the battery, hold down the Option key while you click the battery icon in the menu bar.
You'll see one of the following status messages:
Replace Soon - The battery is functioning normally but holds less charge than it did when it was new.
Replace Now - The battery is functioning normally but holds significantly less charge than it did when it was new. You can still use your computer, but if its performance is affected, take it to an Apple authorized service technician to replace the battery.
Service Battery: The battery isn’t functioning normally. You can use the Mac when it's connected to a power adapter, but you should take it to an Apple Store or Apple-authorized service provider as soon as possible.
Saving Battery Life in Windows 10
The new Windows 10 Battery Saver kicks in automatically when the battery reaches 20 percent of battery life. Depending on your settings, the computer will lower the screen brightness at this time to preserve battery life. To find it, select System from the Settings and then Battery Saver.
You can make changes to the Power Plan screen to preserve battery life. This is the screen where you set the number of minutes of inactivity that elapse before the laptop dims or powers down. Lower numbers reduce battery use. The Power Plan screen is located at Settings > System > Power & Sleep.
If you don't need the internet for a while, you can turn off Wi-Fi and Bluetooth connections to save battery power. The easiest way to do this is to activate the Airplane Mode, located at Settings > Network & internet > Airplane Mode (or Flight mode).
Tips for Maximizing Battery Life
Charge a new laptop computer for at least 24 hours before using it.
Lithium-ion batteries last the longest if they stay between 20 and 80 percent charged.
Remove the battery if you use the laptop plugged into the wall most of the time.
If you won't be using the laptop for a month or more, remove the battery. If you don't have a removable battery, run the charge down to 50 percent before storage.
The battery will drain in storage. If it sits uncharged for long, it can be damaged. Occasionally charge the battery during lengthy storage times.
Avoid extremely hot or cold temperatures. Don't leave your laptop in the car on a summer day or during a winter blizzard.
Adjust the keyboard lighting, sleep settings, and screen brightness downward for better battery life.