Instructables

Solar Bike Stereo

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Picture of Solar Bike Stereo
 In this instructable I will show you how to make a solar powered bike stereo box that fits in a milk crate, which you may already have on your bike!  This instructable assumes you have some proficiency in woodworking and soldering, and is really about the solar to battery circuitry and the options it provides.  This system could be used for any variety of applications that run off 12v DC.

In designing this project the box went through many phases, first it was battery powered, then the solar was added, and more extra bits kept finding their way into the box.  Because of this the photos will appear somewhat inconsistent, so I have provided some easy to read drawings for clarification.
 
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Step 2: Cut List

Picture of Cut List
I used 5/8" MDF and my box is waaaay heavy, you could easily do this with 3/8" or 1/2" MDF to save some weight but it will change the dimensions of your sides bellow.
  Cut sides:
 
1: 12" x 12" bottom
2: 12" x 9+7/8" sides
2: 10+3/4" x 9+7/8" speaker sides
1: 13" x 14" top
1: 10+3/4" x 9+5/8" divider
 

Step 3: Speakers

Picture of Speakers
Cut holes in the center of two of your sides to match your speakers.  You can use a hole saw if your speakers are small enough, or drill a small hole and use a scroll or jig saw.  Solder about a foot of wire onto the speaker terminals and screw them onto the inside sides of your speaker sides so that they fit on the holes you just made.  You can round over the outside edge of your holes with a 1/4" round-over router bit.
bcasey54 months ago

http://youtu.be/T8SBgIgDz_U http://youtu.be/JORVvdxj4Ck
Heres a couple vids on the one I built.

I kept it a bit simpler than is shown in the site by leaving the switch off. I used Velcro to mount the amp and used its volume and switch. I have not built the lid yet but plan to make 2, one plane and the other with the solar panel.

I'm not using the solar panel most of the time because the battery will last a couple days so unless I'm camping with it, I don't think it will be too useful. I also want to keep the weight down. I'm not completely done with it yet. Im considering adding a phone charger in there and might use a cigarette lighter (male/female) setup as for it.

iApple guy2 years ago
Where can I get milk crates?
eastonj4 years ago
And also, why do you not want to solar panel to charge the battery when the battery is in use? would that not be beneficial? or the point for that matter? from what i am reading it seems like in order to use this, the amp is not powered when the solar panel is charging?
mbmosher (author)  eastonj4 years ago
 Right, if the battery is charging via solar, you have to run the amp through AC/DC.  The only reason I do not have the solar panel constantly charging the battery is because the solar panel operating instructions specifically said not to use the battery while it is being charged.  Don't know why.
i asked my coworker about why you wouldnt want to charge the battery while its in use, and he mentioned that the battery's memory could get messed up by it discharging yet remaining at the same capacity. makes reasonable sense.

you've inspired me to create my own. i do not have a bike yet, but i frequent the beach and the wilderness so this is F***ing fantastic! thank you and keep up the good work!
Sealed Lead Acid Batteries don't suffer from memory effect ... only NiMH and NiCad batteries have this problem. This leads me to wonder why the operating instructions say that? Perhaps this causes a problem with the built in charge controller on the Solar Panel? Does it even have a charge controller, or does it only have the diode to prevent reversal?
after doing some Googling here is my best guess of why the warning exists.

If your amp is drawing 2 amps and you have it hooked up to the battery (not charging), then the battery will supply the full 2 amps---simple.

If you are charging your battery at the same time that your amp load is on, then your panel will supply .375 amps (optimally) and your battery will supply the remaining 1.625 amps.

Now for the BUT --- If your amp is on for too long and your battery can't supply the necessary current, then the amp might start trying to suck more power from the solar panel than it can provide---potentially causing overheating and damage to the panel(?).

PV arrays on houses are hooked up to batteries that are constantly being used, so I don't see there being any problem with charging a battery while there is a load attached. House arrays have better backup systems like a charge controller or a generator that can kick in if the batteries are getting too low. Since we probably don't want a generator in our milk crate we'll just have to mind our battery a little more closely.
worth1252 years ago
so great...I love it. Where in the box did you connect the grounds that you soldered together?

Also, am I correct in interpreting that there is nothing attached to the negative terminal on your battery?

Thanks!
mbmosher (author)  worth1252 years ago
Thanks. I think I soldered all the ground leads to a connector that plugs into the battery's negative terminal.
LemurX3 years ago
Fantastic project with totally awesome results! I was wondering though, would it be possible to use a smaller solar panel? I realize the charge time would be increased, but the application I have in mind would be best with a smaller panel. (also a little cheaper) Sunforce seems to make durable panels, so this was the panel I had in mind - http://www.amazon.com/Sunforce-50013-Motorcycle-Powersports-Battery/dp/B001D6GYLO/ref=sr_1_3?s=hi&ie=UTF8&qid=1308374827&sr=1-3
mbmosher (author)  LemurX3 years ago
I don't see why not. The total amp hours of your battery will determine how long it takes to recharge. With a smaller panel it could take more than one day to recharge a decent sized battery.
AMP6783 years ago
This is really cool. How much did it cost?
mbmosher (author)  AMP6783 years ago
I scavenged a lot of it, but basic run down is:

$60 - solar panel
$50 - Amp
$20 - Battery
$70 - Speakers (Car audio I recycled from another project)
$20 - Other stuff (wire, switches, MDF, etc)
$220 - Total

But you could probably save a bunch using different speakers
bjrcboy4 years ago
How long would it take the battery to charge from being completely dead? How long does the music last once it's at full charge? Thanks!
All I can say is, Flogging Molly rock and should rightly be played from a moving speaker in public places!
eastonj4 years ago
 I had a thought about making the boom box so its always charging a battery when its playing music in the sunlight. i came up with using two batterys and no ac/dc plug bc i havent figured out how to wire it. i'm having a hard time wrapping my head around how you soldered all the ground wires together and just put the positives in the switch. i plan on using a knife switch for aesthetics, and thats got me all confused. could you help me out? i drew up this diagram of how i am thinking it should go. 

thank you in advance!
SBB Diagram.jpg
mbmosher (author)  eastonj4 years ago
 That looks like it would work for two batteries, neat idea.  I really did just solder all the ground leads together.  Yes, it was a big lump of wires all in one place, but yes it does work that way.  You don't have to worry about the grounds being switched on and off - it's important that they connect to the same ground so you don't build up charge somewhere else in the circuit.
eastonj4 years ago
with your DPDT switch, can the AC/DC also charge the battery?
mbmosher (author)  eastonj4 years ago
 It's a good question.  The way I have it set up, no.  The solar panel has a built in reverse diode and cut off so it doesn't over charge the battery, which would be a problem if you just connected the battery to the AC.  I imaging with an appropriate battery charging circuit you could throw something it there that would let you charge the battery off the AC, too, but that's what the sun is for!
Nicely done! I really like the fact you now have a self contained "sound cube" that could be taken anywhere there is sunlight. Just ploop it down, add an MP3 player, instant party.
mbmosher (author)  crazybuthappy4 years ago
 Thanks!  Works at night too off the battery, charges during the day.
acaz934 years ago
Wow! I must say this looks really professional! almost like store bought!
Well done!

One more thing, what's the name of the song on the video ?
mbmosher (author)  acaz934 years ago
 Thanks!

The song is Reiga's Bad Habit by Professor Kliq on the Community Service II album.