A solar boombox: because you want to listen to music in the park without purchasing expensive batteries that are bad for the environment; because you don't want to run a cord into your yard while you work; or maybe just because you can.
There are a several solar powered boom boxes floating around on the web. The one pictured above, from Instructables, is my favorite.
According to the author, you can construct a solar powered boombox for as little as $75 by utilizing a small, energy efficient amplifier, cheap bookshelf speakers, battery, a small solar panel, and your own audio input. Supposedly, the Sonic Impact digital amplifier will run directly off a single 1.5 watt solar panel. In case you haven't heard of the Sonic Impact, it's an impressively low power, high quality amplifier that can be purchased for less than $30 (the small gray box in the setup below).

I won't go through all the steps here - you'll have to visit Instructables for the full diy, but here is a list of the materials and tools you' need:
Parts:
- Amplifier
- Solar Panel
- Speakers
- Various plugs and jacks
- A Battery
- Wire
- An enclosure
Tools:
- Soldering iron
- Wire cutters/strippers
- Pliers
- Screwdriver


Resources:
Instructables - DIY Solar Boombox
Another Home Made Solar Boombox diy.

Comments (3)
Interesting concept. Although, I think your opening statement "because you want to listen to music in the park without purchasing expensive batteries that are bad for the environment" completely contradicts what follows.
The Sonic Impact is setup to take 8 AA batteries. IIRC it will play for about 8 hours. Aren't 8 NiCad AAs just as environmentally friendly, lighter, and less expensive than the battery packs you show in the picture?
All the solar panels gain you is the ability to recharge without wall power. From an engineering and implementation standpoint, AA solar charges are much cheaper than 15 watt panels shown above ($60 vs $240 for 2 panels). If you had a second set of AA batteries you could listen in the shade while your second set charges from a much cheaper charger in full sunlight. Otherwise you would need the stereo to be in the sun if you want to take full advantage of solar charging.
Lastly, if your making a fully portable unit it might be better to get a Tripath 2020 PCB from ebay. I got one tested, shipped, and assembled fro $36. That way you aren't buying a SMPS power supply you don't need, and the Tripath 2020 is better than the 2024 which is in the Sonic Impact.
I hope that isn't too critical. I just wanted to express my opinions in case someone is heading down this road.
It would also be good to find the most efficient speakers possible. Those Tang Band FRs are only rated at 85 db/w (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-815).
If you could find a driver with 9dB more efficiency (Fostex) you could play at 94 dB with 1 watt instead of 8 watts. Which means you can play longer on the same charge.
Nice Article...........
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