The solar charger is a stackable shield to Arduino compatible platforms, enables adaptive battery power and act as energy harvester for in-field charging. You may use various batteries that has the voltage of 2.7V-4.2V to shift up for 5V output, or put on Li-ion battery and solar panel to form an autonomous sensor unit. The maximum current provided by the board can get up to 700mA. An USB connector is also useful to charge the battery.