Sunny Buddy Solar Charger Hookup Guide
This Tutorial is Retired!
This tutorial covers concepts or technologies that are no longer current. It's still here for you to read and enjoy, but may not be as useful as our newest tutorials.
View the updated tutorial: Sunny Buddy Solar Charger V13 Hookup Guide
SFUptownMaker 
Hooking It Up
There are three parts to consider when embedding the Sunny Buddy into a project: the solar panel input, battery output, and load.
Solar Panel Input
The input side of the Sunny Buddy comes with a common barrel jack installed. SparkFun's small, large, and huge solar panels all come with this sort of jack installed, and can be plugged directly into the Sunny Buddy.
There are also additional footprints for attaching 3.5mm screw terminals or an additional barrel jack to the board. Please note that if you intend to use two solar panels, you must clear solder jumper JP1 and connect solder jumper JP2. Failure to do this will result in the second supply being left unconnected. If both jumpers are left unconnected, no power will be sent to the board, and if both are shorted, the second panel will be shorted out and contribute no power to the system.
The maximum recommended input to the board is 20V; this is a stack of two of our panels. The minimum is 6V, but most solar panels should be above this.
Battery Output
The output of the Sunny Buddy is intended to charge a single Polymer Lithium Ion cell. A 2-pin JST connector is populated, and will mate up to most of the LiPo batteries SparkFun sells.The load should be connected in parallel with the battery; again, footprints for a 3.5mm terminal or a standard .1" spaced header have been provided.
The charge current is set by resistor R1 in the schematic. By default it comes set to a maximum charge current of 450mA. It's recommended that batteries not be charged at greater than their capacity rating; thus, the smallest battery that should be charged with the Sunny Buddy is 450mAh.
The Load
It's important that the load not be too heavy; since it is in parallel with the battery, it will steal some of the charge current from the battery when it is operating.
To avoid this, consider putting active circuitry to sleep whenever possible, or using a microcontroller to turn parts of the load on or off as they are not needed. Methods for doing this are beyond the scope of this tutorial.