Introduction: Waterproof, Solar BOOMbox AKA: Post Apocalyptic Power Supply

About: String, rope, line, cord, bungee, and all of the things that they can do.

This project was inspired by a friend's build. It's made for extreme circumstances like Whitewater rafting, and after the meltdown of our electrical grid. I'm pretty sure you could throw this thing off of an extreme cliff and it would survive, more or less, intact and working. Also, it is extremely heavy. [OK maybe not Extremely, but pretty heavy] I entered this into two contests, so if you like the idea please vote for me. My friend's original build was very basic, and required a tape adapter to play from another device, like an iPod or such. I saw a couple of features that I wanted to add, for my own sense of functionality and simplicity, so I started collecting materials for my own. The project languished on my bench for at least a year before I heard that Joe was refurbishing his old box. This was the inspiration I needed for getting off my duff and finishing my own box. Now I'm ready for summer!

Here's what I wanted out of this project:
Reasonable battery capacity, ability to recharge itself, reasonable audio fidelity, rugged durability, ability to charge/ power other devices [music players, phones, raft inflaters].
As far as I know, so long as I don't let the battery go flat for too long this box should be able to provide electricity and music for years without ever plugging it into the grid.

Step 1: The Box

I chose to use a 20mm ammo can. It's roughly 17"w x 7"d x 14"h. There's plenty of room for a faceplate including all the accessories and equipment, with enough left over for a music player. I like the ammo can for it's sturdy-ness. I feel like I could toss it off a cliff and it would be no worse for wear.
Other options I considered were Pelican cases, tool boxes, and suitcases.

Step 2: Ingredients

What you put in it is up to you... Here's what I used:
20mm Ammo can.
Pyle marine audio deck. [inputs for 1/8" mini, SD card, USB.]
West Marine water tight, 3 gang, 12v outlet.
A couple of brass bolts. [For aux. power out.]
Super cheap automotive LED accent lights.
Harbor Freight jump-start kit. [Battery, charger, light switch, power switch, battery meter.]
Harbor Freight solar battery charger.

I chose the deck with a couple of things in mind. There is no spinning media [read efficient], it has a weather band tuner [many a traveler has been saved by NOAA's warning of incoming foul weather], it was relatively cheap [$75], it has a variety of inputs for a variety of purposes, including a SD card slot [awesome], and it's supposed to be resistant to wet conditions.

The battery that I harvested from the jump-kit was a 17Ah [Amp hour] SLA [sealed lead acid] and was the perfect size to fit between the walls of the ammo can, below the speaker frames, and left enough room to add a second battery on the day I decide I need more energy capacity. Sadly, after the year or so that this project sat still I let the battery go flat and it crapped out on me [I blame cheap HF equipment]. I had to buy a new one with 18Ah.

[Caveat, I love/hate harbor freight. If it's too cheap to be true, it's probably not worth the time or money you spend. But it IS a hacker's paradise.]

Step 3: Faceplate

I will spare you the painful process I experienced trying to make a layout that worked. Needless to say, it took a long time. I made templates of the various elements and pushed them around until they fit in a way that worked for me, and then just started drilling, cutting and carving out the spaces for all of this goodness.

Once I got all of the layout done it was time to wire it all up. Yet another challenge that would not have made for good TV. Lots of decisions here; what does and does not go to the mains switch, what goes in parallell/ series, how to make the solar panel and wall charger not blow each other up [fingers crossed]. The photos show the complexity. Your results may vary.

Step 4: Speakers

The first speakers I bought were a little too large for my purposes. The baskets [frames] would have interfered with my preferred battery placement. Lesson: check, double check, and check again. Luckily, I had not cut or drilled before discovering the problem.
Once I had a smaller pair, that would work in this case, it was a matter of cutting one big hole and four small holes for each speaker. Measure carefully, mark clearly, cut slowly, and mount with confidence. 
Oh yeah, install the foam gaskets before mounting.
Right now I'm debating how well I want to seal the interface between the speaker and the wall of the box. On one hand, a water tight seal would be great for foul weather and the occasional dunking. But with the lid closed I fear barometric and altitude changes might damage the speakers, so a less than perfect seal might be an advantage.
Someday I will find, and invest in, a two-way check valve to regulate internal pressure without compromising watertightness.

Step 5: Mounting Frame

It took a while to decide how I wanted to make this part. I had it in my mind that I wanted to weld clips into the box. That's one of the things that held this project up for such a long time.
Here I [finally] went back to my original inspiration: Joe's box. He had used a wooden frame to hold the battery and mount the faceplate. Thanks Joe. Your inspiration saved me from myself.
Again careful measuring wins the day. Find the position of your speakers relative to the sides, and cut away the floor plate where it will need to pass by the speaker frames. 
I chose to "swiss cheese" the floor plate. I'm not sure if it will help, but my feeling is that it will provide a little air and cooling to help prevent the battery from overheating.
The rest of the frame I glued and stapled together. I used screws to attach two more pieces of wood that will help lock in the batteries. That way, if or when, I decide to add a second battery, I can move them to where they will be needed in that case.

Step 6: Battery Mount

This step could easily belong to the previous step... But I was so proud of my solution here I added a step just to highlight it.
You know, my old boss hated plumbing strap. And he passed that prejudice along to me. However, there are times when the the "right" solution would require far too much fabrication, time, and money, and a little bit of that ugly, holey [unholy], curly stuff does just the trick. Careful work here will keep you from wanting to hide this piece from view.
But the coolest part is that piece of white plastic sticking out the side. The plastic is Polyethylene [HMPE] like what milk jugs and flexible cutting mats are made of. I cut it to be just long enough to wrap three sides and a little extra to tuck back down the side. What this accomplished is two-fold. It Isolates the battery from the metal sides of the box [I hear that's good]. But the coolest part was that it made the perfect, spring loaded guide that holds the whole assembly snugly inside the box. With it I can turn the box upside-down and the frame stays put. Cool!

Step 7: Final Assembly

In the photo you can see that everything is all set and ready to go. Electrical connections are made, checked and tucked away as well as I expect is necessary. I made the speaker leads long enough to be able to set the mounting frame on the table beside the box, but with the frame on top like this, everything is accessible and can be fiddled with before dropping it all into place. It's useful to have help here, but not impossible to do alone.

Step 8: Enjoy

It works! The solar panel charges, the radio plays, weather is good... Beer is in order.
It works on it's side, or upright, though everything is upside-down when on it's side. Upright focuses the sound in the direction of the listener [efficiency] and still functions as a spare seat in camp. So That's probably how it will work most often.

Step 9: Not Pictured

There are a couple of things I either left out or haven't done yet.
I mounted the solar panel to the inside of the lid with velcro... magical stuff. I intend to add a couple velcro straps to the system so, perhaps, I could mount the panel to a tent pole or nearby tree.
I will also add some velcro to the inside walls of the mounting frame to hold the accessory cords, charging cables, and what-not out of the way.
A paint job is in question. But for now, I'm going punk rock.

There you have it; My first instructable!
Special thanks to Joe who inspired the project and then the work.

EXTREME! Challenge

Finalist in the
EXTREME! Challenge

Car Audio Challenge

Participated in the
Car Audio Challenge