It's been almost a year since I posted the original Solar Shrub on Instructables https://www.instructables.com/id/Solar-Shrub/. It was a great success from the standpoint that it did what it was supposed to do (charge small devices using nothing but energy from the Sun) . Plus, winning the grand prize in the Green Tech Contest was definitely an ego boost! But there were several specific problems with the original design:

1. Low Current: The current produced was too low to charge some devices in a reasonable amount of time. I harvested the original cells from solar garden lights and the specs were quite a bit lower than I initially thought.

2. Intermittent Charging: Because it was generating power real-time and feeding it directly to the USB port, the charging capacity was only at its maximum when the Solar Shrub was in direct sunlight. If a cloud passed over, or the cells were shaded even temporarily, the voltage dropped below 5V and the device stopped charging.

3. Difficult to Assemble: My strategy for the original Solar Shrub was to build “stems” with solid-conductor wires reinforced with wire clothes hangers. These stems were then pushed though holes in a base, bent to 90 degrees, and tie wrapped into place. This turned out to be extremely difficult to assemble, the stems were not as flexible as I would have liked them to be, and I had no easy way to replace a bad stem if needed without completely disassembling the shurb. Plus the solder joints between the solar cells and the solid conductor wires tended to break easily because the wire was too rigid.

4. Vulnerable to Weather: One of the first questions I got about the original Solar Shrub on Instructables was, “Is it waterproof?” My answer was no, but it got me thinking. What if the Solar Shrub was outside charging and it started to rain?

So with these problems in mind, I set out to design a better Solar Shrub!

Introducing Solar Shrub II


Higher Output Current - I achieved higher current by purchasing 8 high-quality solar cells rated at 2-volt x 80mA. Then, with help from Joshua Zimmerman at BrownDogGadgets.com, I added a USB booster and internal lithium battery.

Combo USB Boost + Lithium Charge Controller + Lithium Battery - The combo board boosts the voltage from the solar cells to provide a steady 5V to the USB port. It also charges an internal lithium battery which supplements the cells when they are not in full sunlight. Once the battery is charged, I can even carry the Solar Shrub II indoors for charging devices in the comfort of my home!

Pluggable Stems - In order to make the stems more flexible and replaceable, I decided to use stranded wire instead of solid conductors and attach the stems to the shrub base using 1/8" phono plugs and jacks. Now I can easily plug and unplug the stems as needed for quick and easy assembly and/or replacement.

A Sealed Water Resistant Enclosure - Instead of building the Solar Shrub II into a flower pot like the original design, I built this one as a self-contained plastic “capsule” with all the electronics safely inside. The stems plug into jacks on the top of the capsule which also contains a USB cable with female connector. This design allows weather protection and much more portability. It can be placed into any flower pot or container you wish.

For the latest info on the Solar Shrub Project, please visit my blog SolarShrubs.com.

Step 1: SketchUp Drawings

Before starting to build the Solar Shrub II, I decided to work on my designs with the 3D drawing program SketchUp. SketchUp is a great tool and best of all, it's FREE!

Here are some of my preliminary drawings.

Step 2: Step 1: Materials and Tools Used

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


Soldering Iron
Wire strippers
Side cutters

Step 3: Step 2: 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.

Step 4: Step 3: 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.

Step 5: Step 4: 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.

Step 6: Step 5: 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 chage 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!
What will be the total cost if I had to design it?
<p>i like putting electronics inside plant pots as well :) good work</p>
<p>My neighborhood covenants prohibit solar panels, this looks like a great way to get around them! Maybe I could disguise them as something else too...</p>
Make a solar tree.
FRIGGEN AMAZING!!!!!!! ? I love it... im gonna make one!!! ?... once I take 5 months to *beep*ing get the materials ?
I want one how much
Thanks for your interest! I'm actually working on a manufacturing plan right now. I hope to be able to produce Solar Shrubs at a reasonable cost so I can offer them for sale. Stay tuned at http://solarshrubs.com/
An unbeliveably incredible idea you should really advertise this the ability to dissaseble is great and could you possobly make a mark 2 with a built in voltage regulator to charge anything and keep up the good work looking for a eco friendly chrger for the house and i am totally going to make on of these
Thank you for your kind words!
Thank you, Joshua!
This is awesome! I had read something a while ago, and you've probably heard about it, but it was an array of solar panels formed sort of like leaves using a fibonacci sequence. You could try bending the wires to form this shape and it may help increase its potential!
Thanks! I read that too, but later read that it was debunked. Too good to be true I guess...
Your project is on <a href="http://www.treehugger.com/slideshows/gadgets/make-solar-shrub-charging-your-gadgets/">TreeHugger</a>!
Yeah the writer, Megan Treacy, contacted me over the weekend and asked if she could feature it on TreeHugger! Duh! ;)
Shrubbbbby goodness.
How much would you sell one for? I am interested in one.
Between the cost of materials and the time required to build it, I would have to charge you around $125 USD plus shipping. If I could sell more of them, I could reduce the price of materials by buying in bulk. Then, I would be able to lower the price.
Have you considered getting someone to manufacture this?
I've thought about it, but don't have any experience with outsourcing so I'm not really sure where to start. I'm also not sure there would be enough sales interest to justify the investment. I actually have applied for a patent though, just in case.
why didn't you drill a hole near base to run charging cable through vs coming through top of pot?
The whole thing is self-contained and just dropped into any flower pot, I decided to attach the USB cable to the top so it would not inhibit the shrub from fitting inside of a small pot.
I'm a &quot;little&quot; disappointed. Seeing the introduction photo of the unit <em>inside</em> the house, I thought you had one so efficient it could work under house-lighting, like modern calculators.<br> <br> Of course, with cell phones as the worst offenders, that was a little na&iuml;ve of me.<br> <br> All in all, a nice combination of technology and aesthetics.
That would be great! Unfortunately, solar cells are not that efficient yet. I hope they are some day!
You should sell these!
I would love to! How many would you like to order?

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