This instructable outlines a portable solar charging station, stereo, and LED light that is built into a playmate cooler. It is an all-in-one portable unit, as you can charge your phone or tablet with solar power, fill a room/beach/field with music, and also have an area light.
You can set this up at your home for everyday charging of your devices, and easily bring it with you for a day on the beach, on a camping trip, or anywhere else. It can be very useful during power outages, or even be a prime source of power in an off-grid cabin or home.
The design of this unit is very flexible, and you can choose features or expand on this to meet your specific needs. You can also take advantage of using scrap parts for its construction, with old car audio components, scrap wood, and spare wire that you might have lying around. I've found that you can borrow from a lot of "car accessories" that are 12V DC powered, or even use a small inverter for AC loads, to use this solar power for a wide range of devices.
Step 1: Parts
I chose the 16 Quart Igloo Playmate cooler for this build, since it's big enough to hold everything, but still small enough to carry with one hand. The roll top is also quite useful, and makes access to everything very easy. (~$20, Target/elsewhere)
I used an scrap laminated bookshelf to mount everything on. I've used thin plywood for this before, but a thicker piece of wood makes the acoustics much better. (free/scrap)
Any standard 12V auto/marine stereo deck will work. I used a basic marine unit, since it somewhat more water resistant than a standard car deck. The cheaper units are "Mech-less" and have no cd-player. You could reuse an old unit, and go pick up a used deck from a junk yard / scrap exchange. ($30+ depending on features, Amazon/elsewhere)
I used a pair of 5.25", 150 Watt, 2-way marine speakers, which fit quite nicely given the playmate dimensions. While you could use regular car speakers, marine speakers are waterproof (in theory) and are usually built to take more impact and abuse. Again, this is a spot where you could pick these up on the cheap as used car parts. (~$20, Amazon/elsewhere)
Small 12V AGM lead-acid batteries are very easy to find, as they are used in computer UPS units and fire-alarm systems. Like all batteries, their capacity is rated in Amp-Hours (Ah). Choosing the battery size is a trade-off between Ah capacity and weight, as this is by far the heaviest part. I chose to use two 12V, 8Ah batteries (wired in parallel for a total of 16Ah). At moderate volume, my stereo draws approximately 1 Amp, so in theory I could play music for 16 hours if I drained the battery from 100% to empty. Admittedly, this is overkill, you could get by with 5 - 10 Ah. (~$20 for a 8 Ah battery)
Solar panels are getting cheaper by the day, and you can find a small one on eBay or elsewhere fairly easily. Since the battery is 12V, you want a solar panel that is rated for 12V. The "open-circuit voltage" of a 12V solar panel will be around 18V, but the charge controller will prevent overcharging. The size of the panel should depend on the battery size. As a starting point, I would suggest matching the wattage of the panel to the amp hour rating of the battery (10 Ah battery, 10 W panel), but also considering what loads you will have (a stereo will draw 5 - 20+ W). A 10 W panel will have an effective charging current of approximately 0.6 amps (10W / 18V), which will charge your battery from half to full in about 8 hours of full sun light. I used a 10W solar panel, but this will depend on your needs. (~$35 for 10W panel, ebay)
If you want to charge the system with a solar panel, you will have to use a charge controller to connect it to the battery. These devices regulate the battery voltage and disconnect the solar panel when fully charged, preventing overcharging and damage to the battery. Find one that has a current rating greater than the "short circuit" current rating of the solar panel (the smallest you will see are typically rated for 5 - 10A). A basic unit will do, but I chose a nicer one that has the PCB sealed in epoxy, making it moisture tolerant.
Some units will have a low-voltage disconnect (LVD) function, which will shut off the loads if the battery voltage gets too low, preventing damage to your battery. ($20-$60, Amazon/elsewhere)
- Multiple DC toggle power switches ($5)
- Fuses and fuse holder for different DC loads ($10)
- 12V cigarette ligher socket for accessories ($5)
- Short lengths of wire (scrap/free)
- Drawer handle, to pull the faceplate out ($2)
- LED lights ($10)
Total project costs:
- As built: $250
- Basic components, with same features: $150, (less with used audio parts)