I've been able to continuously power an 80 watt device for approximately three hours without interruption and it could have gone much longer, as well as run an electric drill under load with no hesitation or slowing. This is one powerful machine!
Remember as you construct your device that Volts x Amps = Watts.
There are a couple things to note before proceeding.
1) This is my first Instructable, I hope I get it right.
2) I am not an electrician or a handyman. I'm just an average Joe who used resources available to me and figured out something cool. This Instructable involves wiring. If you are not comfortable doing it or if you don't know what you're doing, learn before doing and don't blame me if you zap yourself.
What you'll need:
1) Battery (I used a 12V 26AH battery that I ordered off the internet for about $65)
2) Inverter (I used a 410 continuous watt inverter that I bought at Wal-Mart for about $35)
3) Charge Controller (I bought one off the internet for about $18)
4) Solar Panels (I used the garden lights that I bought from Wal-Mart for $0.97 each)
5) Electrical wire
6) Soldering Iron and solder
7) Wire strippers
8) Something to bracket everything down
9) "Normal tools" (needlenosed pliers, screwdrivers, stapler, drill, etc.)
10) Dremel tool or sandpaper
Step 1: Prep the panels
Remove the top of the garden lights and expose the screws.
Unscrew the "lid" and set aside (don't throw it away). You should see some hardware (battery connectors, wires, LED, battery).
Remove all the unneeded hardware - this would the battery, the wires for the battery (make sure you don't pull out the panel wiring), battery connector and LED.
Step 2: Solder longer wires
Add a length of wire to each of the wires coming from the panel. This will make connecting them later on very easy.
After you solder the wires, feed them through the hole in the cap and screw it down.
Step 3: Test, test, test
In full sun I was getting about 2.5 volts per panel unit.
Step 4: Construct the box
My box was 12" high, 12" wide and 18" long.
I used 35 panels and each was approximately 1.75" in diameter. If your panels are the same size this is probably the smallest you can go and leave space between each panel.
You'll need to figure out what size you want your box to be and it's going to be based on how much room your panels will take up.
Step 5: Drill the lid
I used one of the panels as a guide to draw the circles to be drilled out.
I used a 1 3/4" boring drill (I think that's what they're called) and it ended up being slightly too small so I Dremeled out the holes to make them a little bigger.
I suggest starting the drilling process on the middle of the lid so you aren't pressing down on the middle when there is very little material left on the outsides of the lid - you may break your lid if you try that.
Step 6: Install panels
Because I got a little happy with the Dremel and made some holes a little too big I used a little gorilla glue to help hold the panels in.
(After using this in the sun, the glue got soft and I had some panels fall through when I was driving up a very bumpy road - I would recommend using copious amounts of glue or finding some other way of ensuring they stay in... I'm still working on repairing mine, any suggestions for an adhesive that won't go soft in the sun would be appreciated).
Step 7: Wire in series, then wire the series in parallel
I had my panels in five rows of seven and that's how I wired them. I had five series of seven (resulting in between 16-18 volts per series) which I then wired in parallel. (I wired red to black, red to black, red to black all the way down. Then I connected the ends (one end was my red end and one was my black end) together and ran them out to the charge controller.)
I used electrical tape to cover the solder points but heat shrink would have been nicer, I just didn't want to buy anything else for this project, so tape was it.
Step 8: Add boxes to your box
I cut out a hole and put an outlet box in the hole and wired the outlet (with some help from the electrical guys at Home Depot and my father-in-law) with the cut end from an extension cord. The male end of the extension cord was going to be plugged into the inverter.
On the opposite wall I cut a hole for a light switch to be able to turn the inverter on/off without opening the box.
Step 9: Mount the inverter
I really screwed the thing down as I don't want it to move. It's pretty solid in there.
I left the switch that is physically on the inverter in the "on" position so the light switch could do turn it on/off.
Step 10: Mount the charge controller
Again, I used the plumbing bracketing and really screwed it down.
Step 11: Mount the battery
Please note - I did not connect anything to the battery yet until everything else was ready to go so I didn't have powered wires as I was trying to hook things up.
I'll explain (and show) the connections in the next step.
Step 12: Hook it all up
This is the order in which I did everything:
1) Panels connected to charge controller.
2) Outlet connected to inverter.
3) Inverter wired to a light switch I installed so I didn't have to open the box to turn it on.
4) Charge controller wired to battery.
5) Battery wired to lightswitch/inverter.
6) You're done!
Step 13: Finishing touches
I put hinges on the lid so it would hinge up and I also put an adjustable support so the lid could be opened at various angles for more direct sun exposure.
I also drilled two small holes in each side to run some rope through for handles.