I'm not so sure 168 LEDs is "nothing". 168 LEDs runing at about 20mA each (pretty standard), is about 3.4 amps of current.
You're assuming that he's paralleling all 168 LEDs at straight 3v.. which would be silly.. as you would be much better off making little mini-series clusters and running at higher voltage.. at least 12v.
Higher V.. lower draw.
junglesmacks, I'm not even concerned
with the topology with this calculation. Don't jump over every current calculation thinking that saving current is the same thing as saving power. I'm calculating how many batteries
he's going to need to power this rig. 12V? 3V? Who cares? The LEDs will each be using 3V at 20mA each, no matter if you put them in series or in parallel. To get 12V you'd need 8 D-cell batteries in series using (168 / 4) * 20mA = 0.84A, with 22AH of juice. With the same 8 batteries I could power the LEDs at 3V at 3.36A but with 88AH of juice. Using a (perfect) boost circuit I could even power the same set at 1.5V drawing 6.72A with 176AH of juice (better check that discharge rate on the battery and the wiring thickness). Guess what? It'll all run the same length of time on the same number of batteries! Power = Current * Voltage remember?
If you want to discuss topologies, that's that's a different matter. Even then, there's no clear-cut solution. I realize that the series-LEDs-current-limiting-resistor topology worked awesome for your suit this year, but it is not the end-all and be-all LED circuit, and not all designs can be built around its ideals. I remember on my own lit-up costume this year I had to power my hat with 6x AA batteries. It sucked having to string that damn thing to my shirt pocket. I would've rather have had a smaller number of batteries that I could change out less frequently, and have left in the hat itself. A single D-cell in a boost circuit would've been nice. Likewise, it may suck having to string together 8x batteries just to power up something portable because it needs 12V of power. The EL wire on my bike used a mere 2AA batteries which was much better than 6x in my hat. Trade-offs.
In Ohmu's case, portability is probably not the major limiting factor. The project should probably design the clusters around the number of eyes
that Ohmu thing has and the brightness
it needs, not around some fixed voltage number. There are other factors as well, such as control resolution; what you gain in longer chains of LEDs you lose in control resolution. Furthermore, it may not even be in his best interest to use high-voltage, resistor-based limiting circuits, or even multiple LEDs to achieve the effect he needs. Single large, high-current LEDs may be easier to work with than long chains of low-current LEDs, and he can employ better powering circuits such as bucking topologies that can cut down on power usage. In the end though, the power usage remains the same.