Powering hundreds of Adafruit's NeoPixels for a cosplay
This started as a comment but got a bit long;
Neopixels / Ws2812s need a 5V regulated supply and do indeed draw 50-60mA per unit when at full brightness.
This is enough to see significant voltage drop down a long string or tape (guess how I know) so the LEDs at the far end of a strip light up red because there's insufficient voltage for the green &amp; blue LEDs to strike up. So, you need a robust power feed to your various &quot;groups&quot; of LEDs - and remember voltage drop gets worse the lower your power supply voltage. 12A down a long wire or PCB track is a significant amount of power.
I would either use one large-ish RC Lipo battery and a few DC-DC (buck) converters near each &quot;group&quot; of LEDs (EG you feed 14V or 18V from the LIPO to a small DC-DC that powers one LED matrix - that way any drop in the wires doesn't affect the metrix) or I'd source a few USB power banks and attach those to the various groups if that's workable - USB power banks do the voltage regulation and easy recharging for you, at the cost of bulk &amp; expense.
Synchronising with your micro is a bit of a challenge if you distribute power supplies, but commoning the grounds solves one side and since the LED control is omni-directional (transmit only), you could maybe use opto-isolators at the LED end to drive the LED data decoupled from the microcontroller voltage. There may be other ways - there's plenty of optical and digital isolation ICs and little modules/boards out there from China that would likely solve your problem.
You can see voltage drop over cable length/size here to give you some indications;
http://fuddymuckers.co.uk/tools/cablecalc.html
12A at 5V gives 1V drop per metre on 1mmsq cable - if you source that same 60w of power from an 18V battery and only regulate it down at to 5V at the last minute you only lose 0.28V/metre in that 1mmsq cable.