DC converter box for USB charging device

I built this to hold small DC voltage converters that I bought on Ebay - http://tinyurl.com/ojm8qbx

Using these plugs: http://www.digikey.com/product-detail/en/0/CP-5-ND

Then wire up a large battery or battery pack to male plugs like these: http://www.digikey.com/product-detail/en/CA-2185/CP-2185-ND/568576

And you are good to go for days on a tablet/phone without an AC source. (I use mine for conventions where it's rare to get an AC power source but you want to take credit cards)