The inspiration for this project came from spending long periods of time in the wilderness without any connection to civilization. Having a mobile power station, that can withstand the elements is incredibly useful when it comes to recharging satellite phone batteries, camera batteries, cell phones, and headlamps. Having it due double duty as a boom box is an added bonus since after many days in the quiet of the wilderness, being able to play few tunes can really help to remind you that you're a human and not some kind of Gore-Tex coated bigfoot wandering the rivers of the west, not that there's anything wrong with that...
Step 1: Materials and Tools
You will need the following materials:
(x1) Pelican 1440 Top Loading Waterproof Case
(x1) Kenwood KMR-440U In-Dash Marine CD Receiver w/ iPod USB (Radioshack # 55039375)
(x1) UPG UB12180 12V/18Ah SLA Battery (Radioshack # 23-1358)
(x1) GOALZERO Nomad™ 13.5 Solar Panel (Radioshack# 55043024)
(x1) Kenwood KFC-P1603MRS 6.5" Marine Component Speakers (Pair) (Radioshack # 55039370)
(x1) Sunforce® 60032 30-Amp Digital Charge Controller (Radioshack # 55038540)
(x1) 12V 8A AC to DC power supply
(x1) UPG D1761 12V/1A Dual-Stage Sealed Lead Acid Charger (Radioshack # 55045644)
(x1) DPDT NTE54-037 - 20A Sealed Automotive/Marine Nylon Rocker Switch (Radioshack # 55050504)
(x1) SPST Rocker Switch (Black) (Radioshack # 275-693)
(x1) Radioshack LED with Holder (Green) (Radioshack # 276-271)
(x1) RadioShack LED with Holder (Orange) (Radioshack # 276-272)
(x1) Binding Post to Banana Plug (2-Pack) (Radioshack # 274-716)
(x1) Marine 12V Power Outlet
(x1) RV Waterproof 110V Power Inlet
(x1) 50-Ft. 24-Gauge Clear 2-Conductor Speaker Wire (Radioshack # 278-1301)
(x1) Red and Black Hookup Wire (18AWG) (Radioshack # 278-1220)
Cable Clips (Radioshack # 278-1640)
3/4" Split Cable Tubing (Radioshack # 278-1654)
Cable Ties (Radioshack # 278-1656)
Insulated Spade Terminals (Radioshack # 64-3125)
Insulated Crimp-On Butt Connector (Radioshack # 64-3108)
Inline Blade-Type Fuse Holder (Radioshack # 270-1234)
Blade Fuses (Radioshack # 270-1082)
Water Resistant Finish
MDF 3/4" panel
Pipe Hanging Strap
Bicycle Inner Tube
100% Silicone Sealant
3-Outlet Extension Cord
6ft Bungee Cord
You will also need access to the following tools:
Hole Saws or Forstner Bits
Drum Sander Attachment for Drill
Step 2: Mark and Cut Speaker Holes
The first step is to start with the initial construction of the unit, and that means cutting apart the enclosure to fit the speakers.
The speakers come with a nifty template for the cut-out that they will need. Use it to mark out the correctly sized circle on the side of the case, and cut the hole out with a jig saw outfitted with a fine tooth metal cutting blade. The fine tooth metal cutting blade slices through the plastic case easily.
I located the hole for the tweeter in the area protected by the handle, it fits there quite well.
Use a drum sander attached to a drill to smooth your cuts out.
It was a little painful cutting apart a perfectly good waterproof case, but with a waterproof speakers and a hearty dose of silicone to seal everything up I was able to preserve a very high level of waterproofing.
Step 3: Mark and Drill Speaker Mounting Holes
Lay the speaker driver into place and mark the screw holes using a metal punch, a pen also works fine.
Then, drill holes for the screws using an appropriately sized bit for your mounting screws.
Step 4: Build Base Board
The inner workings of the boom box will need a base to get strapped down to. Trace and cut MDF into a "T" shape that will fit into the bottom of the case. Attach rubber feet onto the bottom of the panel and set it inside the case to test fit.
The rubber feet help the panel sit inside the waterproof case and make it more stable.
Step 5: Cut Control Panel
Cut a piece of wood (I'm using maple due to it's density and strength) to fit inside the top of the waterproof case and form the control panel. Exact dimensions will vary.
The walls of the waterproof case are tapered at 5 degrees, so I cut the sides of the panel to match by tilting the blade on the table saw 5 degrees as well. This allows the panel to wedge in place.
Cut the length of the control panel on the miter saw.
If anything, make the cuts to be a hair long. The panel should fit tightly in position and can always be sanded down later for a perfect fit.
Step 6: Round Corners
The top of the waterproof case has rounded corners, so the control panel will have to have them too.
I needed a quick way to transfer the shape of the corner of the case to the panel. The easiest way turned out to be using a set of forstner bits to transfer the curve since they come in a wide variety of sizes. 1 1/4" turned out to be a perfect fit for the rounded corner. Trace that curve onto the corner of the panel.
Then, simply sand the corners down to the traced line on the belt sander.
Sand the rest of the edges as necessary until the panel fits in place perfectly.
The tapered walls of the waterproof case should hold the panel in place for test fitting. I decided to install supportive blocks (step 18) to better secure the panel in place.
Step 7: Lay Out Control Panel
Just to be safe, I fabricated a second control panel out of MDF and tested my layout on it first before drilling into the maple.
The control panel will hold the:
- Stereo unit (plays music)
- Solar charge controller (makes sure that the solar panel doesn't over-charge the battery)
- DPDT power source switch (switches between AC and DC power modes)
- Charge controller cut off switch (disconnects the solar charge controller from the battery when the unit is being stored - charge controller draws a small amount from battery when attached even when not active)
- 12V marine cigarette lighter power plug (allows you to plug barrel cigarette lighter accessories into unit)
- Banana jack power plugs (allows access to 12V power source for anything with a wire)
- 120V RV power input plug (water resistant plug that allows unit to be charged when at home)
- AC charging indicator lights (shows charging status of home charging)
- Solar panel charging jack (allows fold out solar panel to be plugged into unit)
Step 8: Cut Holes in Control Panel
Round holes for components were made with drill bits and correctly sized forstner bits on the drill press.
Rectangular holes were cut with a jig saw. Use a 1/2" drill bit to create blade holes for the jig saw.
The control panel I created is a little less than 1/2" in thick. Some of the switches and LED's are designed to mount in panels that are significantly thinner than that. Adapt the control panel by drilling and routing out material from the back so that the area where those components mount is significantly thinner.
See last photo for example of recesses on back of control panel (pictured on the MDF test panel).
Step 9: Prepare Wires
There's a whole lot of wiring involved in this project so crimp on, insulated spade connectors are a must, as well as crimp on quick connect terminals for easy connection to the switch and speaker terminals.
Extend the audio leads on the stereo with speaker wire that runs to the speakers.
Extend the power wires on the stereo, charge controller, and battery chargers with red and black hook-up wire. Solder and heat shrink all of these connections so they are safe/permanent.
Take a moment to take some quick measurements of how long your components are from each other and make sure to cut all leads to be too long, they will be trimmed in a later step. I left around 3 feet of slack in any wire that was going to connect from the control panel to the main case so that the panel could be removed for maintenance.
The Goal Zero solar panel comes with an accessory cigarette lighter jack connected to a female DC power jack. Cut the DC jack off and solder it onto the leads that run into the solar charge controller. I installed my own panel mount cigarette barrel power supply so we won't be needing the one that came with the solar panel.
Finally, grab an inline blade style fuse holder and a 10 or 15 amp fuse and get set to wire that in front of the whole system between the battery.
Step 10: Mount Components
Mount the components onto the control panel.
The stereo head unit comes with a mounting sleeve and fold-out tabs which hold it in place.
Other components are screw in place, like the LED's, the solar charge controller cut off switch and the 12V cigarette lighter power barrel. Others still get mounted with screws, like the AC input receptacle and the solar power charge controller. The banana jacks for 12V power are simply pressure fit in place.
The hardest jack to mount was the solar panel DC input jack. It's a right angle jack on a long wire. I slipped it through a rubber grommet and then epoxied the grommet in place in the panel.
Take the extension cord, cut the plug off it, and use the exposed wires to connect to the back of the RV power supply jack. That way, when you plug the unit in, AC power can be delivered to the battery charger and DC power supply inside the unit (coming up in the step 13).
Step 11: Prepare Bus Bars
There are so many wires to connect I found it easiest to set up two bus bars to connect everything to. There's one for the (+) connection and one for the (-) connection.
These bus bars can get mounted anywhere, but I thought it easiest to mount them to the back of the control panel so they'd be as close as possible to most of the connections in order to keep the leeds short.
Step 12: Extend Charging LEDs
The wall brick SLA battery charger will live inside the unit. In order to see it's status lights, a little bit of hacking is necessary.
Defeat the tamper-proof screws by using a small flat had screwdriver instead of the crazy safety screw head and open up the wall charger.
Once inside, carefully pull out the circuit board and desolder the red LED that indicates "charging" status and the green LED that indicates "charged" status.
Connect some hook-up wire to these positions on the circuit board, cut away a small hole for the wire to exit the plastic case, and close the unit back up.
Now the status LED's can be extended to the control panel so you can see the charging status without having to open up the panel to peek in at the charging brick.
Step 13: Prepare AC Power Accesories
Plug the now hacked battery charger into the extension cord on once side and the AC to DC 12V 8A power supply (I think I'm using one that once powered a monitor) and make a nice little package out of everything with zip ties. This constitutes the AC charging bundle.
Step 14: Install Power
Drop the AC power into the box and push it off to one side. Drop the SLA battery into position in the remaining space and test fit everything.
When the power components are in the correct position, secure everything down with the perforated aluminum pipe strapping. I call this stuff pipe strap, or plumbers strap.
As a safety precaution, insulate the pipe strap with an old inner tube from a bicycle so that it doesn't accidentally bridge any power terminals or short anything out.
Slip the inner tube on, and screw the strap tightly into position onto the base board that was made in step 4.
Step 15: Wiring (panel)
Bundle all of the cables that run to the control panel from the base of the box and encase them in plastic cable housing and zip ties so they'll be strong and safe. Start plugging things in. The basic wiring design is as follows:
The battery powers the stereo, hook up the yellow constant 12V wire to the positive battery terminal. This keeps the station memory and clock going even when everything else is disconnected.
The DPDT switch controls the unit between AC and DC modes. While in DC mode, the stereo is powered by the battery and the solar charge controller is hooked up to the battery so it can charge everything up if the solar panel is attached.
In AC mode, the battery is charged by the wall brick SLA 12V battery charger and the 12V AC to DC power supply powers the stereo directly. This engages the charging lights on the control panel that were extended, as well the additional light on the DPDT switch itself so that the user knows that the unit is in "AC mode". There is no light for DC mode, because, why waste the power?
Using a DPDT switch and running the (+) supply wires through it keeps the two legs of the system - the stereo and the chargers, separate.
With that in mind, connect the charge controller to the bus bars, running the positive charging wire through the DPDT switch. Connect the stereo to the bus bars running the positive wire through the DPDT switch.
Connect the 12V battery charger to the battery terminals running the positive wire through the DPDT switch.
Connect the 12V power supply to the stereo running the positive wire through the DPDT switch.
Connect the accessory power banana jack terminals to the bus bars, as well as the cigarette lighter.
Wire up the RV outlet to the extension cord if you haven't done this already in step 10.
Connect the leads that were extended from the hacked 12V brick style battery charger to an orange and green 12V LEDs thats are mounted on the panel to indicate charging status.
Connect the speaker wires coming from the stereo to the speakers.
Connect the tweeter speaker to the connections on the mid range speaker.
Solder connections where appropriate. Use spade plugs on switches and speaker contacts. Use electrical tape or heat-shrink tubing (better) on all exposed connections. I used some simple three way connectors to extend or branch off of wires in areas too far from the bus bar, where I didn't want to run another wire all the way back (shown on the cigarette lighter barrel plugs in the photos below).
Step 16: Install Speakers
Coat the back gasket of the waterproof marine speakers with silicone sealant and install them into the waterproof case with the provided screws and clips.
Do the same for the tweeters.
Step 17: Wiring (box)
Take the bundle of wires coming from the control panel and connect them to their respective places at the battery terminals, power supply, and wall charger. I used cable clips, zip ties, and zip tie adhesive mounts to manage all of the cables as best as possible so it wasn't a rats nest inside the case.
A 15A blade fuse was wired in front of the positive terminal of the battery to protect all of the components. Note, the stereo head unit comes with it's own 10A fuse, this is just an extra precautionary measure.
Step 18: Epoxy Panel Supports
I wanted to do one better than simply pressure fitting the control panel into place so I cut some small maple supports with that same 5 degree bevel on one side and epoxied them into position in the case so that the control panel was properly recessed.
I found that roughing the surface of the case with sandpaper before epoxying the supports into position helped greatly with adhesion.
Step 19: Construct Solar Panel Bungee Cord Holder
The lid of the case conveniently comes with some mounting points for screw eyes. Insert 6 screw eyes into the pre-drilled holes and thread bungee cord between them in a criss cross pattern. While at the fabric store getting the bungee cord I also picked up a simple toggle to adjust the tension on the cord and used that to join the two ends together.
The Goal Zero fold up solar panel is retained in place when not in use by simply slipping it behind the bungee cord and tightening the toggle.
Step 20: Solar/DC Mode Testing
To test the unit in DC solar mode, switch the DPDT switch to the DC setting and plug in the solar panel. Find some sun.
Switch the SPST solar charger cut off switch to on. This connects the solar charge controller to the battery. The battery voltage should appear on charge controller screen.
If the panel is in full sun, you should see the battery voltage rise. If you start playing the stereo, you should see the battery voltage slowly drop. The louder the stereo, the quicker the battery voltage should fall. In full sun, and under normal playing conditions I found the battery voltage to stay constant over several hours.
To dig in a bit further, I connected a current meter in line with the stereo and tested its power consumption. The current meter read between .5A and 1.5A depending on stereo volume (moderate to very loud respectively).
At best I was able to get the 13.5W solar panel to output at around .75A. That results in best case scenario play times without solar recharging of around 36 hours to 12 hours depending on stereo volume and accessories are being charged. With solar charging you can extend play time significantly. I'll do more testing in real-world conditions soon and repost actual numbers of play and charge times as soon as I can.
Step 21: AC/Wall Mode Testing
AC wall mode is tested by plugging an extension cord into the wall and then connecting the unit through the RV outlet plug. The AC power light on the DPDT switch should come on. Switch the unit into AC mode. Switch the charge controller cutoff switch to on.
If the charge controller switch is set to on, you will see the voltage of the battery on the screen.
If the voltage of the battery is low, the orange light should be illuminated which will indicate that high current charging of the battery is occurring. You should see the battery voltage rise. At a voltage that is determined by the circuit in the charge controller, the wall brick should switch to trickle charge mode, the orange LED light should turn off, and the green LED light should turn on. At this point the battery is fully charged.
If you leave the unit plugged in, the wall brick charger should continue to trickle charge the battery.
Step 22: Accessories
The binding posts and cigarette barrel plug make great connections points for accessories. Plug any cigarette lighter style power plug into the barrel plug and get power. Many different accessories are available, including CFL lights for night time activities, christmas lights for parties, charging for virtually any battery powered item...the list is long and distinguished.
The binding posts tackel just about anything else that you'd like to run off the SLA battery - bare wires, no problem, just thread them onto the posts and tighten.
The head unit for the stereo even has a USB jack that allows you to connect an iPhone or iPod. The stereo controls now run the audio source and charge it up at the same time. What can't this thing do?