Joy-it STROM PI 2 Manual page 5

Switching between USV & Wide-mode
Both operating modes can be selected via jumpers on the upper side of the
board - Please note the markings on the board.
Both jumpers must be reconnected in case of a mode change!
High-power-USB
One of the biggest disadvantages of the Raspberry Pi is that the USB
outputs do not have a high power. So the operation of a USB hard drive is
not possible for example the application of a media center or a NAS.
With the StromPi 2, you have the opportunity to expand the Raspberry Pi
with a high-power USB connection and to enable a higher power output of
the remaining USB-ports.
For that, you must connect to the second microUSB-port which is marked
as "Data IN, Power OUT" a common microUSB-cable - connect the other
side of the cable with a free USB-port at the Raspberry Pi.
Thereby, the USB-Port of the StromPi 2 is connected with the Raspberry Pi
and can supply this way the Raspberry Pi depending on the voltage source
with up to 3 A current. Even the remaining USB-ports of the Raspberry Pi
have the opportunity to obtain more power.