Instructable user mikesoniat gave us permission to share his awesome project for making a solar shrub for charging your devices. He built the original solar shrub last year with the goal of making a USB solar charger that not only provided clean energy but also looked featured a good looking design.
He won the Green Tech contest on Instructables last year for the first version and now he's back with a new and improved solar shrub project that has a higher output current, an internal lithium battery for indoor and outdoor charging options and a sealed water resistant enclosure to protect it.
Click through the slideshow to learn how to build your own solar shrub and start charging your gadgets with solar power.
Materials and Tools
Materials for Power Circuit:
1 – Combo USB Boost + Lithium Charge Controller (BrownDogGadgets)
1 – 1,300mAh Lithium Polymer Battery (Li-po) (BrownDogGadgets)
1 – USB extension cable (Male to Female)
1 – USB cable with micro end
Materials for Leaves and Stems:
8 – 2V x 80mA Round Solar Cells (Futurlec #SZGDDIA58)
8 – 1/8" (3.5mm) Stereo Panel-Mount Audio Jack (Radio Shack #274-249)
8 – 1/8" (3.5mm) Stereo Phone Plug (Radio Shack #274-284)
1 – Roll 24-gauge speaker wire (Radio Shack #278-1301)
10 – Feet 14-gauge solid wire (Green)
1 – Roll 3/16" x 8 Ft. Green Shrink Tubing (Harbor Freight #66766)
Materials for Enclosure:
1 – 4" PVC Cap (Lowes)
1 – 4" Blank Cover (Lowes)
1 – 1/4" rubber grommet
1 – Tube silicon sealant
Building the Power Circuit
Instead of building my own charging circuit this time, like I did with the original Solar Shrub, I contacted Joshua Zimmerman at BrownDogGadgets.com and asked for advice. Joshua recommended the Combo USB Boost + Lithium Charge Controller. This single board takes inputs from the solar array, boosts it to 5V for USB charging, and at the same time charges a lithium battery!
I desoldered and removed the full USB output connector so I could solder my USB extension cable directly to the board. But first, I had to drill out the PVC cap, insert the grommet, cut the male end off of the USB cable, and pull the cable through the hole in the cover. I actually drilled 9 holes in the cover; 8 to accommodate the phono jacks plus 1 for the USB cable.
Then, I soldered the USB cable and battery leads to the circuit board and added a little hot glue to the connections. I also hot glued the battery itself to the bottom of the circuit board to keep the two secured together.
Assembling the Base
The Solar Shrub II base consists of a 4" PVC cap with a 4" PVC cover attached with silicon sealer.
I wired the 8 phono jacks in series-parallel to get the desired voltage and current capacity and then wired the micro USB cable to the solar cells.
I wired four series pairs of cells in parallel with each other. Each series pair of cells produces 4V x 80mA. Four pairs wired in parallel produces 4V x 320mA.
The phono jacks have threaded posts, so I attached them to the bottom of the PVC cover using the included collar nuts.
Finally, I plugged the mini USB cable into the combo board input port, placed everything inside the PVC cap, and sealed it up with silicon sealant.
Building the Leaves and Stems
This time I decided to make the stems pluggable. That way, I can easily remove them as needed to fix, modify, or try different designs without having to disassemble the Shrub.
Each stem consists of a length of 2-conductor speaker wire with a 2V round solar cell soldered to one end and a 1/8" audio plug soldered to the other (matching polarity of course). I also included an equal length of 14 AWG solid conductor wire and green shrink tubing for stability with just the right amount of flexibility.
First I soldered the solid conductor to the metal shield of the phono plug. Then, I soldered the speaker wires to the + and – terminals of the plug. I added a piece of small diameter shrink tubing to one conductor to ensure electrical isolation between the terminals.
Next I slid the green shrink wrap over the entire assembly and added the phono plug's screw on hood. I had to cut about 1/8" off the narrow end of hood to allow it to slide over the shrink wrap.
Finally, I soldered the solar cell to the other end of the stem and heated the shrink tubing. And voila! One stem down, seven more to go!
I used a variety of lengths of wire from 6" to 10" to make the shrub look more like a real plant.
Putting It All Together
At this point, there's nothing left to do but plug in the stems, bend and shape them to look like a real plant, place the entire thing into a flower pot, and take it outside for testing!
First I set it up in direct sunlight to see if it would charge my iPhone 4S. Success! It's hard to see the charging screen in the bright light so I snapped several pics.
After charging for a while, I took the Solar Shrub II inside for the "real" test. Can it charge my iPhone without sunlight (after the battery has a charge)? Again, Success! As you can see, the shrub is charging my iPhone indoors with only it's internal lithium battery!