DIY Solar USB Charger!

\”Are YOU Ready?\”

Happy Wednesday, folks!

Before we get into the neato item I played with the past couple days, I wanted to announce that The Astounding Rooikat is the winner of the cap from www.justicecaps.com that I reviewed last week. To keep it fair, I put all the names in said Justice Cap, and had my 13-year-old son choose a name. Congrats! If you could please contact me with your mailing address at [email protected] I’ll get that right out to you!

On to the post!

I’ll admit, I love my cellphone.  Probably way more than someone who tries to stay self-sufficient should. I use it for the obvious phone functions of calling, texting, taking pictures, social media, etc., but I also use it as a tool when I’m outdoors. The Trimble GPS Hunt app, ActInNature app, and a couple GPS/geocaching apps populate the screen and get used with regularity, making it a nice, easy-to-use digital addition to the compass and map that generally stay in the backpack for emergencies. I know some may scoff, but it’s a great to show you exactly where you are at any given time within a few feet on a topo, road, aerial, or other map. Plus, of course, if it has reception, it can be used to summon help in an emergency or tell your wife that, no, you can’t get a gallon of milk – you’re on top of a damn mountain!

But, as anyone who runs a smartphone knows, with all the accessories, such as GPS, wireless access, Bluetooth, and big, bright, high-definition screens, they just RIP through batteries. Like Whoah. With normal use, I get about 10-12 hours of use before I have to worry about charging the phone. Turn that GPS on to track yourself moving through unknown territory on an app, and you can halve that battery time. So, swell, neato, it works great…until you’re in the middle of nowhere and the battery goes in the red. Hopefully you’ve been keeping track on your physical topo map where you are and recognizing landmarks, and not depending on this phone to get you back to the car. (See Jarhead’s fantastic Compass Orienteering series, linked on the main page on the right hand side, to help yourself out in that department!)

So, what are solutions, if you wanna use the phone, for whatever purpose? Well, you can keep the damn thing off, use it sparingly, but that still just delays the inevitable. You can carry extra batteries (if your phone allows it – my Motorola can be pulled apart to swap batteries, but iPhones can’t.), and that works okay, but you have to keep track of which ones are charged, and which aren’t. And they run out too, especially if you’re on an extended foray. I did some research online to try to find useful solutions… enter Brown Dog Gadgets. (www.browndoggadgets.com)

I’d heard of people making USB-port chargers from Altoids tins, and so I did a web search for that, and it brought me to BDG. This neat website has lots of info, parts, and kits to make all kinds of neat little doo-dads, from noisemakers to robotics to….solar chargers! Just what I was looking for. I looked about, and found the Solar USB Kit. This little baby was just what the doctor ordered, some assembly required. I forked over the $22.99 (shipping brought it to $29) for the 4 volt, 60mA kit. It arrived about a week later.

Here’s what I got in the kit: (minus the Altoids tin…I had that.)

Clockwise from upper left: 4v solar panel, two rechargeable AA batteries (damn nice of them to include batteries!), battery case, 1N914 diode, USB converter port, and two lengths of black wire. To attempt this hijinkery,  you will need the following tools:

-A soldering iron

-Solder (I used .022″ rosin core)

-Tin Snips

-Hot glue gun and glue

-Electrical tape

-Wire strippers

Assembly

Since instructions didn’t come with the kit, I went to the kit-referenced instructions on the website. First up: Wire up the solar panel. The Solar panel is available in different power levels: 4 volts (the one I got since it fits in an Altoids container), 4.5 volts, and 7 volts. The bigger panels will charge the batteries or the device faster.

To start, we strip the ends of the two loose black wires that came with the kit. We attach one of them to the diode. The Diode is kind of a one-way check-valve for the power…it ensures the power from the solar cell goes TO the batteries, but not back out, draining the batteries. I know the photo above has a red wire shown…pretend it’s black. Wrap the stripped end of one of the wires around the side of the diode with the BLACK BAR (you can see how the diode has a black stripe on the body closest to the wire). Solder it on.

Then solder the other wire on the other side of the diode to the POSITIVE tab on the solar cell. Again, pretend the wire is black.

Next, solder the other loose black wire to the negative tab on the panel. Snip off the extra lengths of diode wire.

We’ll need to attach the black wires that run from the solar panel to the black and red wires that come from the battery box. This is as simple as twisting them together, then soldering them together. Combine the wire that comes from the POSITIVE tab on the solar cell to the red wire on the battery case, and the wire that comes from the NEGATIVE tab to the black wire.

As you can see in the picture of the USB converter above, it has two contact points, one positive, one negative. Solder the corresponding wires (where they were twisted and soldered together) to the correct tab (red to positive, black to negative)…and your wiring is complete! Very easy, and I am definitely in the “amateur” category when it comes to soldering and wiring.

Before I mounted the USB converter, I tried everything out…the little red LED glowed when I snapped the batteries in, indicating a charge, and lo and behold, it charged my cell from the batteries! Huzzah! I had a beer to celebrate and had my son pat me on the back.

The battery pack snaps right into the Altoids container perfectly, and stays right in place. There’s actually room for a four-cell AA holder, which I plan on upgrading to ASAP for extra voltage and power capacity. I snipped the battery retaining tabs off of my case like it recommends in the instructions; it makes battery swapping MUCH easier.

To mount the USB converter, line it up on the side of the tin, where you will want the USB port to have access. I made a couple little red lines to guide me, then I grabbed my ancient tin snips and cut it away, leaving about 3/16 of an inch of material remaining.

I set the USB converter in place, and plugged the phone in. I noticed a very slight arc, and the Altoids tin started getting hot, which told me the circuit was grounding out to the tin. So I took some black electrical tape and laid a layer where the metal parts of the converter would touch. Success! Everything worked great.

The  instructions say to liberally hot-glue the converter to the tin, but alas, I was woefully devoid of a hot glue gun. So, being the balls-to-the-wall electronics rebel car guy I am, I just J-B Welded the shit out of it. Worked great and I got a “resourceful dude point” according to my son.

The whole works can then be fit into the Altoids tin, with just the USB port visible on the side to tell anyone otherwise. I like the tin idea, because it gives the whole system a convenient armor plating of sorts, and depending on type of Altoids you got, a wonderful minty aroma.

Cable not included in the kit.

The really cool thing about this kit is that the USB port is pretty much standard and universal these days, and charging cords for pretty much everything are made to fit this USB. I tried my wife’s iPod, her iPhone, and my cheapo mp3 player…all of them charged with this setup, making it quite versatile.

Testing the charger

After a couple days of screwing around with my new toy, I did discover a few things: AA batteries are 1.5 volts apiece, making this setup put out 3 volts on batteries alone. The two cellphones I looked at in my household had 3.7 volt batteries, so this will not charge from batteries alone. Thankfully, the solar cell is 4v, and it does just fine charging a 3.7v battery with good sun. Since I have the room in the tin, and since it’s as easy as de-soldering a couple wires and soldering new ones, I’m going to upgrade to a 4-AA system. That will give me 6v of output, more than enough to charge my cellphone (though I suspect the 4v solar cell will only charge up to 4 volts.). Also, this kit will charge devices on just the solar cell alone, no batteries required – providing you have adequate, direct sunlight. I tried charging the batteries with the solar cell on the dashboard of my truck; this doesn’t work, as auto glass has coatings that limit UV ray penetration. If I rolled the window down and put the charger on the seat in the sun, it worked great. Roll the window up, it stops charging. Just a heads-up. It will also ONLY charge rechargeable batteries. It will charge FROM non-rechargeable alkaline batteries if the sun isn’t available, but those batteries won’t play nice when trying to charge them.

This is a killer little setup to charge your rechargeable AA batteries (well worth the extra money, by the way) too. After a couple hours in the sun, the batteries had a full charge (from what I could tell) and when inserted in my Mini-Maglite, it shone as bright as it ever has. So, on a good sunny day, you can charge up several rechargeable AA batteries and have them good to go for whatever purpose you may deem them worthy.

It also is very light, compact, and rugged enough so that I don’t feel bad about dropping it in a zip-lock bag and it finding its way into my BOB and camping gear. The initial cost, having to buy the solder, electrical tape, kit, and shipping, was about $36 all told. But now, I can make a few more of these kits as money and time allow (entire elapsed time to construct this charger, even with mistakes and reading instructions, was about 20 minutes) and have them in my vehicles, give them as gifts, whatever. It’s a neat idea, practical, and pretty snazzy. I think I’m going to try putting velcro on the back of the solar cell and and on the back of the Altoids tin, so I can just mount it to the velcro pad on my backpack and have it charge as I walk around.

What do you guys think? Comment below and stay safe!

-TRW

P.S. If you’re not too Radio Shack-savvy and want one of these, I bet you could sweet-talk me into building one for ya…maybe my dog will like the mints. Lord knows he needs them. Contact me at [email protected]