This simply isn't true -- not anymore, at least. Most smartphone, laptop, accessory and AA or AAA chargers are smart enough to momentarily stop charging once the device is fully charged.
How do I re-charge my laptop battery?
Power off your laptop and allow it to charge until it is fully charged, while it is powered off (not sleeping/hibernating). Unplug its power adapter, then power on your laptop and use your laptop battery until it depletes its battery. Fully charge your laptop again in order to recalibrate the charging sensor. Expand the 'Batteries' section.
What is a fully charged battery?
A fully charged battery provides the operator with up to 24 hours of standby time and the ability to run up to 20 full cycles at room temperature. It is a 12-volt rechargeable battery with 4.5 AH (amp hours). The backup battery is an accessory and has a one year warranty from the date of purchase.
If your device has Smart charging turned on, the battery level will be set to a lower level that's better for the battery overall. Your device may not charge to 100%, which helps keep your battery healthier in the long run.
How does smart charging work?
With Smart charging, you don't need to worry about unplugging your device to keep it from staying charged to 100% for longer periods of time—Smart charging handles charging for you. If your device has Smart charging turned on, the battery level will be set to a lower level that's better for the battery overall.
When Smart charging is on, you'll see a heart on the Battery icon in the following places—on the right side of the taskbar and in Power & battery settings. When your hover over the Battery icon with your mouse, it says Fully Smart charged and means the battery isn't charging even though your device is still plugged in.
When should I Turn Off Smart charging?
When working for longer amounts of time in places where you might not be near a power outlet. When you think you may need the full capacity of your battery. Because each device manufacturer implements Smart charging in slightly ways, visit your device manufacturer's website to learn how to turn it off for your device.