Waterproof, Solar BOOMbox AKA: Post Apocalyptic Power Supply




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.

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    18 Discussions

    If any of you want to see how this project is done by a real pro, check out Noahw's build. Nicer equipment in every way. [except for the sideways speakers :)]

    2 replies

    Well, to be honest, I didn't keep track. I had to purchase a couple of things twice because of failure to plan/ etc. Something like $45 for the box, $75-95 for the deck and speakers. $40 for the battery. The rest I had laying around. I think you can get that solar panel [which is undersized] for $15. And a jump kit with a fresh battery is pretty cheap too. If I knew what I spent on some of these projects I'd probably quit doing them. :)

    I am building this panel now and was wondering what the small LEDs are for? Did you use a regular 12V power supply and just wire it in to the panel.

    1 reply

    The 'jump kit' I used for some of the parts had a light switch which operated a poor excuse for an incandescent bulb. So I found some cheapo leds at the auto store. Useful at night, and gives off an dim/ eerie glow. At present I charge the battery via a really basic wall-wart type trickle charger with alligator clips on the external posts. No power supply but for the battery. Also a note: If you have a leak in your garage roof, avoid placing the open box directly under the drip... I haven't had the heart to fire it back up after discovering it half full of water the other day.

    New update: Discovered, what I believe to be a critical flaw in my system.
    The solar panel hasn't got enough juice to overcome the natural discharge rate of the battery. According to a friend of mine who sells batteries and solar chargers teh minimum output value [in amps] for the solar panel should be 1/10 of that of the battery's capacity [in amp/ hours] for it to effectively charge. The panel he showed me that would barely comply with that is about 4 times the size of the one I've got... So, next time I have the notion I'm going to try to find 3 more like it and stitch them together. Kinda like Noahw's charger but ... hackier... That said, with any luck that won't happen for a long time... I have stuff to do, so until then... Sayonara.

    The HF solar charger seems to be ineffective. I am replacing the tiny charge controller-in-a-car-plug with a more robust charge controller.
    And the charging input plug from the jump kit is also a dud. [I'm thinking that's why the original battery went flat, and would no longer charge.] In the short term I've replaced that with an off the shelf battery charger. Hoping to find a suitable connector to get from there through the faceplate.

    2 replies

    I was thinking of doing something similar with a 12v laptop power supply. would that work to charge the battery while the music played?

    A power supply will charge the battery, but I don't think it has a means to stop itself before the battery explodes... Could be wrong. A simple wall charger works well and can be found pretty cheaply. That's what I've ended up with, and it seems to be working well.

    And, by the way, awesome project! I love things in 20mm boxes! I raft (a lot) and we store all kinds of goodies in ammo cans...even poop in the 25mm ones.

    2 replies

    Along popular riverways it's common for people to carry out their waste. Imagine a hundred people a day pooping along the riverbank... It's a good rule. Some rivers require you show your system before issuing a permit.

    Finally got out on the river with this box! It played music all day, and still had enough juice to inflate my 16' raft at home afterward. I do need to go back in and sort out something with the charging systems...

    Advise: to prevent charger or solar panel conflicting it is good to add a big diode in the direction of the battery, this way there is also no leakage current back to the charger or solar panel: battery stays full when not charged. Keep in mind what the charging current and differential voltages are: diode must be able to handle the current and diodes have a small voltage drop as a result, if the battery is 13,8V and the diode needs 0,7V then the charger should be at least 14.5V. Check the actual values before ordering the diodes!

    Bosch powerbox professional radio beats every radio normal persons can make: made to withstand a 9meter drop on concrete, rain proof, and a lot of sound, only setback is 250$, or 300 for the extra charger function, more sound and remote, but both are the best money can buy... You can use it at a party outside with 50 guests and it is still too loud!

    Well, I used the electronics that came onboard with the solar panel and the jump kit.
    The solar panel's circuitry was built into an automotive 12v cigarette lighter plug. I ripped the board out, replaced the built in fuse with an inline type from the auto parts store, and wired it directly from there to the battery.
    Same goes for the wall charger. I ripped the circuit board out of the jump kit, and wired it just the same way it came.
    I did no research on what those electronical elements actually do, I simply assumed that if I stuck to the same general configuration as the original, I'd be just as safe as the manufacturer intended.
    In short, I shot from the hip.
    I would guess that if you are including a charge controller you should run all of your charging sources through it.

    I'm curious on how you wired everything up. I just happen to building something extremely similar to this and wanted to know more about what you mention in step 3. I've got a 12V battery that I'd like charge from a solar panel, with a charge controller, and also by wall plug with 12V DC transformer. The battery powers a car stereo as well as some 5V USB accessories. How did you wire yours up so that the wall charger didn't dump power to your stereo, but did charge the battery at 14V. I'd love it if the solar panel and or wall plug could charge the battery while the stereo played. Thanks for any input you might have!