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.

Step 1 Materials

  Parts you will need:
 

wire

dayton t-amp

car speakers

12v battery

solar panel (Sunforce 5watt trickle charge)

milk crate

mdf

tompsons water seal

polyfil

milk crate

DPDT switch

M-F Audio Cable

Power jack and plug (to match whatever your amp comes with!)

8 threded inserts

assorted screws

  Tools you will need:

Soldering Iron

Table saw

Clamps

Screw driver

Drill

 

Comments

[iApple guy]

Where can I get milk crates?

[eastonj]

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]

 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.

[eastonj]

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!

[worth125]

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?

[worth125]

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.

[worth125]

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]

Thanks. I think I soldered all the ground leads to a connector that plugs into the battery's negative terminal.

[LemurX]

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]

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.

[AMP678]

This is really cool. How much did it cost?

[mbmosher]

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

[bjrcboy]

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!

[ciaran.mooney]

All I can say is, Flogging Molly rock and should rightly be played from a moving speaker in public places!

[eastonj]

 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!

[mbmosher]

 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.

[eastonj]

with your DPDT switch, can the AC/DC also charge the battery?

[mbmosher]

 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!

[crazybuthappy]

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]

 Thanks!  Works at night too off the battery, charges during the day.

[acaz93]

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]

 Thanks!

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