Your Garmin GPS contains a lithium ion battery that charges when you connect the device to a computer or other power source, and even charges when you use it in your vehicle. If you charge the Garmin without using it at the same time, you cannot tell when the battery is fully charged. To check the Garmin's power level, you only need to power the device on and look at the battery icon on the screen.
Connect the Garmin to any suitable power source. To connect it to your computer, plug the USB cable into the Garmin's USB jack, then plug the cable into a free USB port on the computer.
Wait for up to four hours for the Garmin to charge completely. Your Garmin may not need to charge for four hours if the battery is not fully discharged.
Press the "Power" button on the Garmin to turn it on. The green battery icon in the top-right corner of the display represents the available battery power. If you see three green bars, this indicates a complete charge.