As part of my practice I make paintings and drawings with embedded LEDs controlled by an Arduino clone and LED driver. I showed 10 new pieces during an exhibit recently and had great feedback but there were a few of the inevitable comments about "the wire" (i.e. the wire to the wall wart transformer).
I'd love to lose "the wire" and power these through some combination of solar panel and rechargeable battery. I'm no electrical engineer but the bit of research I've done leads me to believe that this is no trivial technical task. Combine that with the fact that most installations of work like this in the home (office, restaurant, etc) would not be in an area getting full sun and that even if it were possible, hanging work in direct sun has a harmful effect on it. And then there is the additional cost, whatever that might be.
So…before I conclude that it is not viable (technically, economically) I thought I would ask for more informed opinions. Spec-wise, in these current versions, there are 64 LEDs (average 2.3-3.3v), an Arduino running at 5v and a Maxim7219 running at 5v. No realtime clock to sleep the piece.
Would it even be possible to charge solar cells/recharge a battery under typical indoor, non-direct sunlight lighting conditions?
Best Answer
Voltage doesn't matter without information about current.
Your power requirements
You have 64 LEDs there, but at same time you probably have 50% of them turned on.
Typical LED maximum current is between 10-20mA. Your LEDs need 2.3-3.3V but your supply is 5V. You should reduce supply voltage to 4V (as Ignacio suggested in comment).
For 32 diodes:
You will need 10W (thats at least 30x30cm size) or even much bigger solar panel to power it in building (no direct sun). Solar panel rated at 10W have maximum power of 10W, and thats rating for direct sun light.
So - technically - thats bad idea.
However you can try to extend time on battery with few small solar panels. They will look good in your art.
If you are really want to use solar power
You can use one of phone solar battery chargers from ebay. Prices start at 15USD, these cheap chargers are probably total garbage, but you can try. Everything is there - rechargeable battery, charging circuits, constant voltage output. Just disassemble it and put its guts into your painting.
You can reduce power requirements by adding some movement sensor to detect people in front of the painting. It may be infrared or microphone (needs less power).
Another idea - you can use photoresistor to measure light and make some adaptive brightness.
And for god sake - remove these wires during exhibition, use any kind of battery!!! :)