I have battery power needs as well and have a 12v battery - here is my current direction.
Purchased some of these 12v to 5v power adapters with 1.2amp current capabilities. They should come in today or tomorrow.
http://www.ebay.com/itm/250838285454?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649#ht_6598wt_1185
This is the battery:
http://www.sears.com/shc/s/p_10153_12605_00911221000P?prdNo=1&blockNo=1&blockType=G1
The above battery ran a color cycle pattern on 70 LEDs for 45 minutes using an inverter. When the car chargers come in I will compare times and report the difference and any other issues / information that may be helpful.
Any ideas, suggestions or feedback on this power method is appreciated.