• USB Type C - On the edge of the board is the USB Type C connector. It has 5.1k CC resistors so it will work with any computer or power supply to get 5V and up to 1A.
• VIN - This is the solar panel or DC power input to the bq25185. Connect a 5 ~ 18V power supply. If the input is a solar panel, the charging chip will adjust the current draw so that the voltage does not dip below the battery, thus optimizing the solar power input.
• VU - This is the power input from the USB connector. 
• G - common ground.

At the top of the board is the JST battery connector. By default, the output is 3.7V nominal / 4.2V max battery chemistry/voltage for all modern 1-cell LiPoly or LiIon batteries with a default charge rate of 1A.
This output is available on the bottom of the board as well, labeled BAT on the board silk. You can use this secondary output to monitor the voltage on the battery with a multimeter.

• 4.5V - This is the load output, labeled 4.5V on the board silk. It provides a regulated 4.5V-max load output. No matter what voltage you have on the USB or DC / solar inputs, the load output port will never go above 4.5V due to an internal voltage regulator. Keep this in mind, though, when dealing with high currents and high DC voltages as the LDO will make the board start to overheat and throttle the current.
  
• - - This is common ground.
• 3V - This is the regulated 3.3V output from the separate buck converter. It takes the load output from the bq25185 and switches it down to 3.3V at 1 Amp max load. This output is available on the bottom of the board as well, labeled 3V on the board silk.

• D+ and D- - USB positive and negative data lines

• EN - This is the enable pad for the 3.3V output from the buck converter. Bring this pin low to disable the 3.3V output.

On the back of the board is the charge rate jumper. You can cut this jumper to change the charge rate from 1A to 500mA.

• 3.3V Output LED - In the top right corner of the board is the 3.3V output LED. It is the green LED. It will be lit if the 3.3V output is enabled.
• Charge LED - In the top left corner of the board is the charge status LED. It is the orange LED. It is labeled C on the board silk. It will be lit while a battery is charging.
• Fault LED - Directly below the charge status LED is the fault status LED. It is the red LED. It is labeled F on the board silk. It will be lit if the board experiences a fault condition. The bq25185 has integrated fault protection for a few conditions:
  
  • Input overvoltage protection
  • Battery undervoltage protection
  • Battery short protection
  • Battery overcurrent protection
  • Input current limit protection
  • Thermal regulation and thermal shutdown
  • Battery thermal fault protection
  • Safety timer fault
  • ISET and ILIM/VSET pin short/open protection.