For those who missed it earlier in the thread, here
http://www.markmalmberg.com is a link to my website that shows the existing piece "Albireo" in a prior installation in Philly. Two Arduino-controlled sculptures communicate wirelessly by XBee, interacting in motions and sounds. I monitor the voltage state with the Arduino so I can use the motors more when there's more power available, and less when the voltage is low. In the middle of the day, there's lots of activity, the motors are much more involved and the battery gets charged with 1.8A and discharged with bursts of up to 5A or more. The cap will handle this part of the day really well and last just about forever doing it.
For the next installation in Albuquerque, there will be a third similar piece, and I'm rebuilding kind of everything to eliminate some weak links and to formalize the electronics much of which is currently wired point-to-point. I have some things also to get working that didn't get finished last time - encoder reading, some Hall sensors, amplification of the audio etc.