What Happens If a Laptop Battery Is Overcharged?

It isn't possible to overcharge a laptop battery. Leaving your computer plugged in after 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 its battery life.

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.

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, open the Apple menu and go to System Settings > Battery. You'll see one of the following status messages, depending on your version of macOS:

• Normal: The battery is functioning as expected.
• Service recommended / Replace Soon: The battery is functioning as expected but you should consider replacing it because it's not holding a charge as well as it used to.
• 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 11 & 10

The Windows Battery Saver feature kicks in automatically when the system reaches 20% of battery life. Depending on your settings, the computer will lower the screen brightness. The controls for this are in Windows 11's Settings > System > Power & battery > Battery saver. Windows 10's is Settings > System > Battery Saver.

You can also 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. These options are available in Settings > Power & battery > Screen and sleep (Windows 11) or Settings > System > Power & Sleep (Windows 10).

If you don't need the internet for a while, enable Airplane Mode to turn off Wi-Fi and Bluetooth. One way to turn on Airplane Mode is in Settings > Network & internet > Airplane mode (or Flight mode).

Tips for Maximizing Battery Life

Batteries last considerably longer when you maintain them according to industry best-practice guidelines. Here are some ideas:

• 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.
• Remove the battery if you won't be using the laptop for a month or more. If you don't have a removable battery, run the charge down to 50% before storing it. 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.
• Lower the keyboard lighting, sleep settings, and screen brightness for better battery life.