Q: Looking for a portable IPAD to printer system, battery powered-no wifi

This Epson printer is the only one I've found that says that it can print from an iOS device via Bluetooth:

https://pos.epson.com/products/MobilinkP60withBluetooth?ProductPK=679

The printers that support AirPrint require WiFi, though some can act as their own access point and thereby set up an "ad hoc" WiFi network. Whether you'll find any that are battery powered I don't know; WiFi takes quite a bit of energy.

Regards.

Check out what mobile printers Print n Share supports.

Make Portable Printing Easier with Print n Share and the Brother RJ-4040

http://prmac.com/release-id-44494.htm

see makethisstuffwork post in:

https://discussions.apple.com/thread/4987217?tstart=0

Brother PocketJet® 673

-- Prints on a variety of 8.5" wide thermal media.

-- Print PDF files from your iPhone and iPad with the PJ-673 Print app

http://www.brother-usa.com/Mobile/ModelDetail.aspx?ProductID=pj673-k&PG=26#.UeX0 Z18pDDJ

"Mobi Print gives its users the capability to use iOS devices to accomplis iOS mobile printing, such as iPads, iPhones, and other Apple products, to print with any of Zebra’s mobile, CPL, & ZPL printers. "

http://www.arrowheadphx.com/mobi-print/

HP has released the 1200w NFC Print Accessory which makes the HP 100 or HP 150 mobile printer (both battery powered) work with iPad. Here is a setup video: https://www.youtube.com/watch?v=9zVfCpT4X84

Check out mobi print.  This is the only platform built specifically for what you are asking for.  It has a new ios 8 extension and the system doesn't need a network at all to print PDF, images...etc.  It will resize any PDF to the correct attach printer. 

Mobi Print website - www.mobiprintapp.com

Mobi Print on app store - https://itunes.apple.com/us/app/mobi-print/id701088704?mt=8

You will need an imz320 (cheapest device zebra has) to print the receipts.. they are around $300. We are testing a new device in the low $200's though but it isn't released yet.