What Happens If a Laptop Battery Is Overcharged?

Tips to maximize laptop battery life

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, keeping the battery consistently on the charger may not be the best idea if your goal is to optimize the battery life of your laptop.

Lithium Batteries
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Lithium-Ion Batteries

Most modern laptops use lithium-ion batteries, the same as in many smaller consumer devices like watches and flashlights. These batteries charge hundreds of times without affecting battery life.

Lithium-ion batteries feature 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's 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 these types of batteries plugged in after being fully charged doesn't affect the battery life appreciably.

Mac Notebook Batteries

The Apple MacBook, MacBook Air, and MacBook Pro use non-replaceable lithium polymer batteries to provide maximum battery life in a compact space.

To check the health of the battery, press and hold the Option key while you click the battery icon in the menu bar. You'll see one of the following status messages:

  • Normal: The battery is functioning as expected.
  • 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.

Save Battery Life in Windows 10

The new Windows 10 Battery Saver kicks in automatically when the system reaches 20% of battery life. Depending on your settings, the computer will lower the screen brightness. To find it, go to Settings > System > Battery Saver or right-click the battery icon in the system tray.

Make changes to the Power Plan screen to preserve battery life. Power Plans 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 SettingsSystemPower & Sleep.

If you don't need the internet for a while, turn off Wi-Fi and Bluetooth connections to save battery power. The easiest way is to activate Airplane Mode, located at Settings > Network & internet > Airplane Mode (or Flight mode). It's also available from the Action Center window.

Tips for Maximizing Battery Life

Batteries last considerably longer when you maintain them according to industry best-practice guidelines:

  • 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% 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% before you put it in 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.
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