The PWR block was primarily designed to include voltage regulators that provide 3.3V and 1.65V (midpoint) to power the system and peripherals. It also includes a built-in battery charger for greater convenience; note that the USB socket found in this block is just used for charging.
With the battery connected to the JST socket, when the user slides the power button to the ON position the system should powered on and ready to use. In the ON position, the system WILL NOT CHARGE and any USB cable connected to the system should be REMOVED.
To charge the battery, the power button needs to be in the OFF position. Once a USB cable is connected to the USB socket, a red LED indicates that the battery is charging; when the battery is fully charged the LED will turn off.