Introduction: Solar Radio Boombox Stereo
What is a Solar Radio Boombox Stereo?
The solar radio part is a low power head unit that will play for days on battery power. The Boombox Stereo part is an amplifier and 5 1/4" speakers that will blast out music at 98dB.
This project describes the assembly of a portable solar powered AM/FM radio and digital media player equipped with Bluetooth, USB, AUX, and SD-CARD inputs. The design is intended to be water resistant and be somewhat rugged. The Solar Radio Boombox Stereo also features an LED courtesy light along with a digital volt meter to display battery charge level. 5V and 12V charging ports will be added later.
The with the exception of the solar panels everything is housed in a plastic water resistant "ammo can" dry box with a lockable clasp and rubber lid seal.
AM/FM reception, Bluetooth, USB, SD, and AUX inputs are provided by an automotive type, marine grade, single DIN, dashboard radio head unit. The unit I choose is self contained and has 2 internal speakers of its own. An external 16" rubber mast antenna is attached to the rear of the unit to provide increased reception.
Nothing pricey here but it does add up. I got the radio, amp, and speakers for just under $40 but the total cost of the project can go up to $200 depending on your choice of components. I had some stuff on hand so its hard for me to say exactly what you might have to spend to make your own.
- Amplification is provided by a DROK 2-channel amplifier rated at 35W RMS output per channel
- Speakers are 2 waterproof marine grade 5 1/4”, 100W (50W RMS), 2-way mid range, and surface mounted.
- Batteries are 2 12V 12Ah SLA (Sealed Lead Acid) wired in parallel to provide a total of 24Ah @ 12VDC
- Charge controller is rated at 10 Amps providing charging and load protection via separate outputs.
- Solar panels are 2 20W 12VDC and provide over 3 Amps at peak performance.
- Home (AC) charging is provided with a “wall-wart” transformer rated for .5 Amps @ 14VDC (19v OCV)
- Color coded LED rocker switches control radio(ACC supply), amp/fan, voltmeter, and LED courtesy light.
- Cooling is provided by a 40mm variable speed fan.
Whatever I didn't have I purchased on Amazon. I've included links to some equivalents of that stuff too.
A decent radio that will play for a long long time without plugging it into the wall.
This would require enough battery power to play the radio during the day while charging and enough stored power to serenade us late into the night. It should also hold up for a few cloudy days too. This will be used for camping weekends and weather emergencies which for me would be a hurricane that could knock out the power for days or weeks.
Re-use $50 worth of batteries
I had on hand 2 big ole (almost new) SLA batteries salvaged from a dead UPS that are actually perfect for this project. Not only do they possess a lot of Amp hours but they also weigh a lot and hold the unit down. Lighter batteries might not offer that benefit. Vibration is an issue that is minimized by the mass of the batteries. They are heavy though and I may be looking at lighter alternatives when its time to replace them.
A repairable device
A radio with easily replaceable parts. If any particular component goes bad I can replace it or even upgrade without the constraints of an off the shelf system.
A radio with good reception.
A lot of times there are no bars when we go camping. The phones don’t work so no music streaming, no news, weather, or sports either. Being surrounded by a forest of 70 ft trees is nice but it can limit any unlimited plan. You can't always count on having cell coverage to provide you with important news or entertainment. The external antenna helps pick up signals from far away even among those trees.
Weather resistant and rugged design.
While a completely waterproof design was desired, in this case it is a benchmark that is hard to achieve. There are constraints of sound amplification and battery technology that require ventilation to resolve. No SLA battery should be stored in a completely airtight enclosure due to the possibility of the battery releasing gas, which for SLA batteries is hydrogen, and other nasty stuff.
- understand basic circuits Electronics Class
- use and read voltmeter/multi-meter How to Use a Cheap 3$ Multimeter to Test Voltage or Amperage
- strip and tin wire How to Strip and Tin Wires Like a Pro
- crimp connections
- heat shrink connections
- determine bolt and hole sizes
- drill and debur holes
- use a hole saw
- use a miter saw or cut-off saw
- use a jig saw or cutout tool/router
- use a screw driver and wrench
- basic math and fractions
- read a ruler or tape measure
- use a sliding square to mark locations
- think spatially
- Wire cutters and crimp tool
- Soldering iron
- Scissors (for heat shrink tubing)
- Heat gun or blow dryer
- Power drill and bit set
- Hole saws 3/4” and 1”
- Jig saw or cutout tool/router
- Deburring tool or file set
- Phillips screwdriver
- Small wrench set
- Utility knife
- Bolt cutters (usually on crimp tool)
- Hot glue gun
- Miter box and miter saw or cut-off saw
Design and layout
- Tape measure or 16” ruler
- Sliding square
- Sharpie with ultra fine tip
- Painter’s tape
- Self adhesive shelf paper
- Electrical tape
- 1/4” x 2” PVC molding
- 1/4" wood or ABS sheet 6 1/4" x 12 3/16"
- Stainless steel hardware
- Wire ties, wire hangers, and wire loam
- Sound absorbing mat (I used vent filters)
- A CD or DVD (to trace speaker cutouts)
A note on Terminology
Weather resistant doesn’t mean just rain so it encompasses water resistance as well as just about anything else you could encounter outdoors like heat, cold, ice and snow, wind blown dust, and of particular concern here in Florida, humidity. So while water proof is attainable it is expensive and complicated and while it’s possible this unit may take a swim it is highly unlikely. It's more likely to be used al fresco so I’m going for a goal that is more robust and reasonable which is a Weather Resistant device.
Love your batteries
Batteries perform better at moderate temps and over heating can not only cause the release of dangerous gases it will have a negative impact on performance and battery life.
You should really think of batteries of this caliber like a pet. Most importantly the box you carry them in has to have air holes! Besides that they have to be tended to. You’ve got to keep them charged and they can’t get too hot or too cold. If they are mishandled they will bite with bright white sparks. If you run them too hard they will suffer and die. Love your batteries and they will love you.
Feel the heat
The electrical amplification of sound generates heat as well and can cause damage to the amplifier and other components in the system if the heat is not regulated and dissipated. This is usually done with a heat sink that requires moving air to provide cooling to the amplifier chip(s). In a closed case this would be a small volume of air and would not provide the desired effect without some communication with a larger volume of air outside the case.
Cooling can be provided by
- the amplifier chip abutting the wall of the case and mounted to an external heat sink
- a Peltier thermo-electric cooling system integrated with an external heat sink
- a water cooled loop between an internal and external heat sink
- a small fan and a couple of holes in the case to let some air circulate
All of the options on the list except for the last are complicated and expensive. So my design has holes in the case to allow ventilation for both safety and cooling. I found a couple of places on the box where the holes are kind of protected by the shape of the box and proper placement should keep out a moderate amount of rain. Dust can be controlled with some filter material and they can be sealed with some electrical tape. While this unit is water resistant, it is not water proof.
Step 1: Choosing Components
Choosing the Head Unit
The approach I am taking revolves around a standard single DIN automotive dashboard radio. Known as a head unit, this one component incorporates all of the input functions required for to process digital media. AM/FM radio, Bluetooth, AUX, SD and USB are all included in one unit. It even comes with a remote. While more powerful head units are often full size (7x2x9) and require a 10 amp circuit or more, other less expensive (power sipping) units will be shorter and require less install depth.
The unit in this example is only 3” deep and requires less than 3 amps. It has its own speakers so if I really want to save power I can leave the amp turned off. Like wise with the amp cranked up the radio mute button only turns off those speakers. That's not really necessary since they actually kind of compliment each other with the smaller speakers filling in the top end.
Matching The Speakers
Speakers come in a variety of sizes and styles and should be matched close but above the output of your head unit or amplifier. This project isn’t about speaker design and acoustics so don’t expect Hi-Fi sound. I have an amp that outputs 35w on 2 channels so I’m going with a pair of 5 1/4” 100W (50w RMS) for around $15. Even at this low end I get about 98dB with minimal distortion.
How Big is That Battery?
“Not big enough” is the only correct answer. That being said I admit these batteries are big enough but not by design. The batteries for this build came from a UPS that is no longer with us. After the smoke cleared I was left with $50 worth of batteries and no where to put them. This project is partly just to get some use out of almost 20 lbs of batteries.
Thinking in the Box
I went with plastic instead of metal for a number of reasons. Weight, workability, price, and availability. With almost 20 pounds of batteries I don't need more weight and plastic boxes are designed to hold the same heavy loads. For workability there is no comparison and the price was fair enough at around $15. With the size of the batteries, head unit, and speakers in mind I was careful to chose a box with smooth sides and square(ish) dimensions. I didn’t want to have to work around anything on or in the box.
Its worth noting that some of the ridged boxes are thin walled so they require irregular shapes for strength. You may want to avoid these due to sound quality issues. This box is nice and thick, about .010 and doesn’t vibrate like its another speaker.
Even after checking and double checking the sizes it was hard to anticipate exactly what I was getting. I had to order online after looking in the local retail stores and not finding what I wanted. Sure enough, the dimensions were correct, but only for the middle part of the box. I hadn’t noticed and a slight taper wasn't mentioned. It was enough to make me change my idea for placing the batteries. More on that in the Layout section below.
On my command – CHARGE!
The solar charge controller provides a lot of neat things that are needed for a battery powered system. In addition to regulating the solar panels it also provides over load and over discharge protection. The controller will shut things off if the battery charge gets too low. I chose one of the cheapest controllers available since it was all that is needed and its a model that is widely used.
The batteries will normally be charged by the solar panels but they just need to be fed some voltage and the controller is not that particular about where it comes from as long as its within the specs. For a backup charger I am using a wall wart plugged into an AC outlet. This wall wart is a “Class 2” transformer that provides 14 VDC which is enough to charge this type of battery. This is not a PWM “adapter” and provides 19VDC OCV (Open Circuit Voltage) which drops to 14.2 when plugged into the controller.
To modify the wall wart, the mono-plug was cut from the power lead and an SAE “Bullet” 2-pin, quick-disconnect connector added from 1/2 of a 12" jumper, the other half went on the solar panels. The solar panels and the wall wart can both be connected to the unit via a single SAE, weather proof port. I chose the SAE connectors because I had some on hand and they are low cost. They work great but can be hard to disconnect. You can use whatever type connector for the power supply that is suitable for you.
A Switch in Time
I had some random switches I had planned to use but I wasn't satisfied with them. They appear in some of the earlier photos. I replaced them with the round rocker switches. They are not rated as waterproof. There are waterproof options I would probably go with if I did this over. They take too long to ship so they didn't make it in this build.
The standoffs protect the face of the radio and are cabinet handles from a local big box home improvement store. These handles come with mounting screws which have to be shortened to use with the thin walled box. Use the bolt cutter on your crimp tool or thread a nut on them and grind them off.
The 12V port is an SAE plug with a waterproof cap. There are other options but this style of connector is compatible with a variety of 12V devices I already have on hand.
The map light is a "tag light" with 3 LEDs.
The antenna is a 16" rubber mast external mount.
All mounting hardware with exception of the standoff screws is stainless steel. Anything less will rust sooner or later, even in the desert. Stainless steel will buy you quite a bit of time before that happens. Don't cheap out on the screws or you will regret it.
Step 2: Testing and Layout
Inspect and test each component as soon as possible. Look for defects and try all the options. Also check the compatibility of all your components. Do this part as soon as possible to make sure everything is working together okay. Try to get everything hooked up as it will be once it is installed and go through everything again. Take notes to keep track of what you're seeing and hearing. I also used a laser thermometer to check for heat build up at various stages of the build and after it was complete.
Watch out for shorts while you're testing. I made some sparks fly by not paying attention. Insulate any bare metal on the connectors using electrical tape if you have to. Just remember its temporary. Make sure all the switches are off and hook up the battery last.
I got the Bluetooth Blues
I tested everything and all was fine. I even stuck the speakers in the box to get an idea of the sound. I thought everything was going to work out great but I didn't have the amp close enough to the head unit to pick up the Bluetooth interference I would notice once it was mounted. Once the amp was mounted right next to the head unit it started hearing the Bluetooth conversation. I'm convinced this is an EMI problem as the amp worked flawlessly just a few inches away from the head unit. It is now positioned right next to it and anytime a BT device is paired you can hear the BT signals. They seem to go away if the BT device is actually sending data (like a song), but my ears are old and your results may vary. I don't use BT enough for it to bother me. All is not lost if that's a deal breaker.
I was aware of this possible interference and actually had the amp mounted where the 12v port is on the side of the unit. It worked fine there so I took a chance and put it where it is now. I wanted the convenience of having the controls as close together as possible. Its too late to go back so I'm stuck with it for the time being. It's not that bad and I may be able to use some foil or a ground loop to minimize it. I have yet to put a USB charge port in so it may end up there if I can find a new space for the amp. If you're really into the BT you should go ahead and change your design to put the amp a little further away from the head unit or eliminate an amp altogether with a more powerful receiver.
I had no idea of how this would end up and approached the layout from a top down perspective. Starting with the largest components I determined how each would fit within the space of the box. The switches and standoffs were then placed after the big pieces were positioned.
When I started I didn't have any of the parts except for the batteries and I ordered the box based on their dimensions. The published measurements made it look like this was possible but they turned out to be an average of the width and depth since the box tapers from top to bottom. They said 6" wide and the bottom of the box is actually 5 3/4" while the top is larger at 6 1/8". Same with the long side of the box. They said 12" which turns out to be 11 7/8" at the bottom and 12 1/4" at the top. Luckily the batteries just fit. I wanted some air space on the ends but it should be okay. It just goes to show you can never be sure of just what you get when you order online.
On that note remember to NOT use the sides of this box to draw your lines. The sides are not square. You have to work off of the top or bottom of the box to make your measurements.
The switches were placed as close to what they control as possible. The antennae went on the back towards the hinges to keep it out of the way when the lid is opened. The charging port and map light went where there was some space left over on the end.
Inside I used the PVC molding to create a cradle of sorts to provide the batteries with 1/4" air space underneath and on the side. A additional piece of PVC on each support holds the batteries in place with the only remaining movement being straight up. This upward movement is suppressed with a 1" x 1/2" bar of ABS plastic bolted to the front and rear of the box spanning the middle of the two batteries. I have yet to drill the front hole and screw it in since the back seems to hold it just fine.
These batteries only last a few years so they will need to be replaced eventually. With the limited space in the box this could be tricky. My goal for the design was to keep things out of the way so that nothing had to be removed to get the batteries out. The only thing that gets in the way is the head unit and it will slide forward enough for the battery to clear without removing it. Just two spring clips on each side of the head unit hold it in place.
The charge controller cover was removed for better cooling and it was mounted directly to the rear of the box using 6x32x1/2" machine head screws. The LEDs were bent up and over the top of the controller board and can be seen through the back of the box. I cut the section off of the controller cover that held the LEDs. By slipping this over the LEDs it cuts down on light coming through the rest of the box.
Step 3: Wiring
There are 3 Separate Circuits
The Supply circuit provides incoming charging power to the controller.
The Battery circuit feeds power to the battery and draws power for the load when neccessary.
The Load circuit provides power for the devices in the box.
The Supply circuit is power by solar panels or an AC "wall wart".
The Battery circuit is isolated and protected by the charge controller from faults in the supply or load circuits.
The Load circuit is distributed via terminal posts to 4 devices each with a fuse and lighted switch.
The 4 devices in the Load circuit are the stereo head unit, the amp, the map light, and the cooling fan.
In the wiring diagrams above each load device connects to the terminal posts and one pair of wires runs from the terminal posts to the controller.
The "Master Switch" is a DPST switch that disconnects the supply circuit and the battery circuit at the same time. If your charge controller has an on/off switch you probably don't need this.
Wire colors and sizes vary because I used some I had on hand. Normally red is the "hot" positive wire and black or white is the "common" or ground wire. The amperage and lengths in this project don't dictate the need for really thick wires but I would not go over 16 gauge. I used 16 gauge with some heavier wire for the larger loads like the feed to controller and the terminal posts. All wire is stranded.
For outdoor use you should definitely tin your wire leads. Its kind of a hassle and merely a preference but I highly recommend it. It's your call but make sure you have the lengths figured out first. Space is tight and extra wire gets in the way. It's no fun snipping off a tinned lead only to have to do it over.
You should minimize splices and run lengths from connection to connection. If you have to lengthen a short wire consider redoing it or altering your design first. It's worth it to avoid that extra possible point of failure. I tried to work with what came with the parts. I was able to crimp connectors on the component wires and stick them right into a fuse or terminal without any extra lengths or splices. If you do have to splice wires don't be tempted to solder them together. IMHO soldered connections belong only on a board. Use a (mechanical) butt connector with heat shrink tubing and don't forget to tin those wires.
A lighted switch requires it own circuit. This circuit is completed when the switch is activated and routed via a connection on the switch to the negative side of the circuit. This means you will have an additional ground lead for every lighted switch you use. Since I positioned each switch close to the device it controls I was able to piggyback the ground lead from the device to the connector on the switch and run a single negative wire back to the terminal post.
Fuses come first. DC power flows down the positive lead. Get the fuse as close to the source as possible before any switches and components. A fuse on your negative lead will only blow after a surge goes trough everything else in the circuit! Fuses should be matched to the power requirements of the circuit and as close to but above that rating.
Use a little tough Love! Once you crimp your connections you should really yank on them to make sure they are tight. If they come out you are not doing something right. Check your sizes. Connectors are color coded for the wire size you should use. Also make sure the color codes on the connector and crimp tool match up. Make sure you line up the connector and are pressing the top of the crimp down on the top of the connector then really squeeze it hard. Stand on it if you have too. Use short lengths of pipe to extend the handles for better leverage if all else fails or if you broke your leg standing on your crimp tool.
As a rule of thumb (and most of my fingers)
Safety Third! As long as its first and second that is. Don't think this stuff is harmless. It can burn you or start a fire. While you are working on this don't leave things unattended without unhooking the battery power first. Make sure to keep your batteries safe from anything falling on the terminals. Tape works. Call me paranoid but I usually unplug things like soldering irons too just to make sure they are off even if they already are.
P.S. As of this writing I still have all of my fingers except for the tip of one thumb lost a long long time ago to an errant utility knife. Be careful!
Step 4: Cut Outs and Though Holes
After you have made your measurements and marked off the locations get out your safety glasses and start drilling. You need a pilot hole for each speaker and the head unit. The pilot hole should be large enough for the jigsaw blade to fit into.
Make your cut outs for the speakers and the head unit. Save the material you cut away. I used these scraps to test different glue and make washers and spacers.
Each switch requires a 3/4" hole. Use the scrap from these holes for the standoff washers. If you use a paddle bit you will have to fabricate the washers from your scrap pieces.
Drill the holes for the standoffs on 3" centers. The clearance holes for the standoffs should be tight so pick a drill bit as close to the bolt size as possible. I cleaned up the scraps from the 3/4" hole saw and used them to add some meat to the sidewall of the box. The screws they came with have broad heads which should cover the pilot hole made by the hole saw.
The antenna requires a 3/4" hole. I put it on the back 1 1/4" from the top and side. I positioned it toward the side of the box with the hinges.
The power port also requires a 3/4" hole for the wires to pass through. Center this hole 1 1/4" from the edge and the same distance down from the hinge support. Once this hole is drilled insert the port and mark the 4 mounting holes. The clearance hole for these can be a little loose since there are 4 and hard to get lined up.
Do the same thing for the map light. To get get it straight trace a line across the side at the proper height using your sliding square. Measure across to find the center of the light once its mounted. Mark that spot and drill the center hole for the wires. Then insert the lamp and get the 2 mounting holes lined up on your marked line. Mark the locations, remove the lamp, and drill the holes.
Make sure to clean up the plastic shavings. They are not biodegradable and should be disposed of properly (or re-used improperly) Just don't let that stuff get spread around there's enough out there already.
Step 5: Mounting Components
I didn't use any caulk or glue on the mounted components. I did it this way so that things can be removed and or replaced easily. Most surfaces match up and seal pretty good already so it would be overkill.
I had planned to glue PVC strips to the inside sides of the box to mount things to but nothing really sticks that well to this plastic. I had the best results with hot glue and used that for the battery cradle. While it holds pretty well I didn't trust it enough to hang the components from.
The head unit has a metal sleeve that slides into the cutout. Metal tabs on the sleeve are bent behind the box wall to hold the sleeve into place. The head unit slides into the sleeve and is held in by a spring tab on each side.
The speakers were mounted with the included hardware which is meant for use in a blind install where you cant reach around the back of the speaker. Since I can reach the back I used these like spring clips with both sides behind the mounting surface. I didn't have any foam to use for a gasket but if you do take the time to cut out a ring to go in between the speakers and the box do it.
The amplifier just hangs from the potentiometer (volume knob) which is bolted to the box. There was no other choice without being able to glue a mounting block for it. This should be okay for such a light unit. Time will tell.
The voltmeter requires a 1 1/16" hole for mounting. I was able to use a 1" hole saw and sanded the hole to fit the meter. You only have to take off a 1/32" all the way around.
The antenna and round rocker switches require a 3/4" hole for mounting and the switches have a key lock that requires a small notch on the side of the hole to keep the switch from rotating. Use a small square file or your utility knife to make the notch.
The 12V solar charging port is attached to the side using #6 x 1/2" stainless steel machine screws.
The standoffs are cabinet handles mounted with the supplied screws and backed up with washers made from left over material from the cutouts.
I fabricated a set of terminal posts on a strip of PVC. I used brass screws and gnarled nuts for binding the connectors. The PVC strip was later mounted to the side of the box using one of the mounting screws for the lamp.
Top It All Off
The primary purpose of the top panel is for space to mount things to but it also keeps the interior closed off when the lid is opened. You may or may not need this part depending on how you mount your components.
For the top panel I used a 1/4" ABS plastic sheet cut to fit the opening. I got this from a friend who had it left over from a project. I'm not sure where he got it from. If you cant get ABS use plywood or a thin board. I cut the panel to size on a table saw to get nice clean edges.
A through hole was drilled to mount the master switch which was placed to clear the top of the lid when its closed.
The cooling system was hot glued to the bottom of the panel. This part is still in development since I wasn't sure of what size or how many fans would be needed to keep things cool. I have since tested the unit and the single 40mm fan seems to do just fine in the mid 90's with a heat index of 100 F.
Update: The hot glue did not hold up and the fan fell off so I made brackets for it. I made these out of two metal strips that came with the radio. They are intended for removing it from a blind install and since I can reach the back of the radio I don't need these. I drilled holes on the ends of each strip and bent them around the fan frame with tabs sticking out to mount it to the underside of the top panel. To mount the brackets I drilled shallow pilot holes and used small 1/4" long self tapping screws offset with washers to keep them from poking out the other side.
Once my new batch of switches arrive I will mount the fan switch next to the master switch and bolt the speed controller to the bottom of the panel with the knob sticking though so adjustments can be made without lifting the panel. Unlike the box material the ABS takes to the glue well so the cooling fan will remain glued to the panel.
Update: For turning the fan on and off I used a switch I salvaged from the dead UPS. I used my utility knife and pretty much carved out 5/16" pilot holes to get the 1" x 7/16" rectangle shape required for the switch. It was a pain but the switch was free. I put the fan switch here because I won't be using it that often. Once its on it will stay on and vice versa. The fan doesn't pull that much power at full speed (.07A) and the controller isn't necessary. I just had it laying around and put it in for even more for extended range. If you think it will always be hot (or cold) when and where you are using this go ahead and skip the controller and get a 2 wire fan around the same rating.
I drilled a 3/8" hole for the fan speed controller knob and mounted the fan speed controller board under the panel. I used plastic brackets leftover from installing window blinds. I cut off some of the excess plastic and used the offset to clear the screw heads in the tight space where the board was mounted. Again I used short screws with washers to keep them from going through.
I also sleeved the fan wires to keep them in order and added plugs to the power leads so the lid can be completely removed. The plugs should be wired so the the receptacle is on the "hot" side coming from the terminal posts.
Step 6: Finishing Touches and Follow Up
The amplifier is really great but it came with a cheap plastic knob. I found another one that fit the 1/4" shaft. Its aluminum and has a set screw to hold it on. Looks better too.
I used some 6" x 12" vent filters for some sound deadening. If they can hold up in a heater vent they will hold up in the box. I used about 4 of these between the speakers and the batteries and used electrical tape to secure them to the wall of the box under the head unit. This loose weave material offers some improvement but not much, feel free to pursue your own strategy to fit whatever you have on hand. I would avoid foam rubber or anything flammable.
I started the wire management but ran out of hangers for the wire ties. They are the only thing that seems to stick to the box walls. It does help to keep things tidy but as long as nothing is touching the wrong thing it should all be fine for now. I did tape all of the switches, the battery posts, and all other bare metal connectors except for the terminal posts.
I used a piece of Velcro on the back of the remote to hold it in place on the top panel where it will sit with the lid closed.
I put hinges on the solar panels so they fold up. I wired them together and added the SAE plug from the other half of the 12" cable. I used a pair of self adhesive wall hangers on the back of one of the panels for a place to wrap the extension cable when not in use.
I put a ribbon on the antenna to make it a little more visible and give me an idea of which way the wind is blowing. The ventilation in the box flows from right to left and a breeze from the wrong direction might counteract the circulation efforts of the cooling fan.
The unit sounds great to me for what it is. There's no sub woofer so it lacks any real oomph but the 5 1/4" speakers sound as well as any installed in a car door. If I had to be critical of anything I would say the low end is a little muddy. It's not that bad and by being able to adjust the volume on both units you can really change the sound to your preference.
The head unit by itself is not much to listen too but its bearable and with such a low power draw should it play forever even with very little sunshine.
I have field tested the Solar Radio Boombox Stereo and it performed better than expected. On a 3 day camping weekend it charged while we listened to it on the first day and it played for hours into the night. The next day was cloudy and I didn't even hook up the panels. It played most of the day and into the night. The third day, 36 hours after the last charge, the battery was still at 12.4 volts. Now I didn't really blast it but it was loud enough to drown out distant distractions like loud 4 wheelers and airboats.
The temperatures averaged in the mid 90's with a heat index around 100 F. It was hot and the radio was outside the whole time. Its really hard on the batteries at these temps so the cooling fan is critical to keep things as cool as possible. If its really hot you may not be able to charge at all during the middle of the day without boiling the batteries.
I would replace the solar charge controller with one that has a temperature sensor. This allows the controller to adjust the charge voltage downward when its hot or crank it up when its cold.
I need to add a ground loop to the stereo amplifier power supply and or get it further away from the head unit BT chip.
I would use soundproofing on the inside walls of the box.
I would use switches rated as waterproof.
I would add a signal amplifier on the radio antenna. (Couldn't find a good one that works)
Maybe a sub-woofer?
Besides all that I would do it again the exact same way. It was a very enjoyable project and I'm looking forward to always having some decent tunes no matter where I go.
Questions, comments, and critiques welcome.
Thanks for Reading.