Solar 7-up: Solar Phone Charger in a Bottle

Message in a bottle.  Genie in a bottle.  Ship in a bottle.

Solar phone charger in a bottle.

The time has come.  Drink a peppy beverage of your choice, or drown your sorrows by draining a bottle of Johnnie -- do whatever it takes to get an empty bottle.  And then follow these easy steps to transform it into a solar phone charger.

Time to complete: an hour
A wee bit of soldering required
Difficulty level:  Pretty easy, but broken glass is likely
Number of band-aids required: 1-2

This is the 5th entry in the Solar Pocket Series of projects that Alex (this guy) and I are posting over the coming weeks.   For more about Solar Pocket Factories and DIY solar check out our just launched Kickstarter campaign (Aug 15 - Sept 14):  http://www.kickstarter.com/projects/alex9000/the-solar-pocket-factory-an-invention-adventure

Here's what it's all about in 2 minutes:

++ An old bottle.

++ Either a hand of steel for popping the bottom out of the bottle, or a glass cutting wheel.

++ A playing card. 

++ Copper tape (single-sided adhesive):  This is easy to find at most hardware or electronics shops.

++ 11 solettes:  these are small pieces of monocrystalline or polycrystalline PV silicon that are typically hidden under an epoxy blob in off-the-shelf panels.  You need the raw stuff for this instructable.  Available a few places on eBay or via our Kickstarter page here:  http://www.kickstarter.com/projects/alex9000/the-solar-pocket-factory-an-invention-adventure

++ High temperature superglue aka cyano: the thin stuff, like crazy glue.  The gels don't work well.  The off-the-shelf super glues will work, but for a more reliable panel you will need high temperature cyano, since most basic cyanos breakdown at 80 degrees C (which is a bit on the threshold of what your panel could experience in a bottle sitting on your porch).  I used Aron Alpha 401XZ, which gets to 120C.

++ Soldering iron and solder for just a couple joints.

++ JST connector with a couple free leads.

++ USB cable, plug to receptacle.

++ Lithium battery; I used a 2000mAh LiPo.

++ A lithium charge chip or board.  There are several of these on the market, and they are also available in the phone charging kit on the Solar Pocket Kickstarter page mentioned above.  I use the Seeed Studio LiPo Rider Pro for this charging bottle.

++ You don't need to encapsulate your panel for this project, since the panel will be protected more or less in a bottle.  Although you will get corrosion over time at the solder joints, it will operate for quite a while without any encapsulant as long as your bottle doesn't get filled with water.  However, you can encapsulate with 5-minute epoxy, but note that epoxy is only good for 2 years in the sun.  Better encapsulants are PU designed for doming and high-end solar applications (like solar cars); and another great method is EVA laminate with glass.  More on this method on a separate instructable shortly.

You'll need two pieces of copper tape, to pickup the two poles of the solar panel you are assembling.  Cut, peel, and stick.  Rub it down with the back of your fingernail for that retro gloss finish..

>>Note that the copper tape conducts best along the surface without the adhesive.  It doesn't conduct reliably through the tape thickness.

Now, as with all of the Solar Pocket Instructables, this is the tricky part:

Theory:

This step is the key -- combine solettes in series with a superglued shingling technique.  Each solette, or any chunk of mono or polycrystalline PV silicon for that matter, outputs around 0.5 - 0.6VDC, which is not enough voltage to do very many useful things.  So, we need to combine enough of these solettes together in series so that their voltage outputs add up.

In order to power the LiPo charge circuit, which then pumps current into the LiPo battery, which then charges your smartphone, we need to produce 4.8V - 6VDC from our homemade solar panel.  This means we will need a minimum of 10 solettes in series (or, 5.0Vopen).  The solettes we are using will output Im (or, the max current at the maximum power point of the cells - about max power point here: http://en.wikipedia.org/wiki/Maximum_power_point_tracking) of around 130-150 mA per solette.  So, since we are combining the solettes in series, the voltages add up, but the current does not.  Or, to put it another way, 10 of our solettes in series will output 5.0VDC and 130mA on a nice day in Osaka.

Back to the solettes:  The (+) output is the grey underbelly of the first solette in your shingled stack.  The (-) output of the series connected shingled lineup can be accessed either at the bus bar or white silver ink runners on the blue top surface of the final solette in your stack, or by using a "false" solette that doesn't produce electricity but just serves to bring do the top surface connections to a solette underbelly. This is the easiest and cleanest approach, and is worth the sacrificial solette.  So, ignore what I wrote in the paragraph above -- you need 11 solettes if you are using one as a basic conductor.

What to do:

A few dabs of superglue (again, regular Crazyglue will worl, but breaks down at temperatures of 80C, so I recommend you use high temp cyanoacrylate available in the Solar Pocket Kits or online a number of places, including here), a few seconds of pressure, and you've got yourself a solar series connection!  Repeat 11 times.

Check the output of your freshly minted panel at your two copper tape outputs -- in noonday sun you should read an open voltage of around 5.0 - 5.4VDC and a closed current of, well, whatever the closed current of a single solette is.  For solettes of the area I am using in this project (13mm x 52mm), the closed current is around 130mA - 150mA.  But I cover up around 20-25% of the solettes when I shingle them, so expect an output of around 100mA closed current.

You can make your panel very pretty and waterproof with a few techniques.  This is not necessary for this particular project, because you will be placing the panel in a bottle, which will (mostly) protect it for some time before corrosion sets in.

That said, If you want to encapsulate anyhow, you can use an off-the-shelf 2-part 5-minute epoxy -- just pour it on with your panel suspended on a couple pencils to allow drip-off, and let it set.  This will be pretty for perhaps two years before it yellows and turns to poo, although keeping the panel in the bottle will again help.  You can also use bartop, EVA + glass lamination, and sophisticated doming polyurethanes.  More on these options in a follow-on instructable.  

The lithium charge chip I am using comes on a board called a LiPo Rider Pro.  It has a JST connector input for the solar panel, so I needed to solder on a JST connector to my panel.  (these come with all Solar Pocket Phone kits, incidentally)

Soldering onto the copper tape is a joy, even for people who have never soldered.  It is actually fun to solder onto this stuff.

Make sure to get the polarity right of your connector!  The bottom of the first solette you placed is your (+) connector, and the other copper connection is your (-) terminal.

Now that the solar panel is made, the rest is about the bottling of your energy collector.

There are various ways to get the bottom out of a glass bottle.  I tried this method:


...and my hand ended up bruised.  I think a gorilla or ninja may be able to do this, but I couldn't.  

So, I got a little glass cutting wheel and setup a simple fixture so I could score the bottle bottom.  This worked, more or less, with a lucky key so I could line up the bottom with the top after inserting the panel assembly.

Like so....

Like so...

Now place your bottle in a window that gets good light, or hang it outside on a tree.  

Well done solar hero!!

You can make this with parts you can find online and at some of the links I mentioned.  And you can also make it with the kits on the Solar Pocket Factory Kickstarter page.

Thanks!  If you have improvements to this Instructable, please let me know!

Another Solar Pocket Instructable coming every two weeks....