Portable battery not charging Ipad Air

I know that the Anker site states the output specs for their chargers is 2A, The brand I use (New Trent) states their output is 2.1A. The specs for the official Apple 10W charger is 2.1A and the Apple 12W charger is 2.4A (I'll have to verify these numbers later on on my 12W (at least) charger). I believe the Air comes with the same 12W charger that came with the iPad 4.

Maybe this combined with the increased sensitivity to the Lightning cables is now affecting what will/will not properly charge the devices.

My iPad Air charged from a USB port on my computer, a USB port in my wall outlet and from and Anker portable battery.

Are you using a certified lightning to USB cable? Be sure to use a good cable. Try with the cable that came with the iPad if you are using different cables.

First thing to try is to reset your device. Press and hold the Home and Sleep buttons simultaneously until the Apple logo appears. Let go of the buttons and let the device restart. See if that fixes your problem.

Apple discontinued support for many third-party chargers after the incident in China when someone got electrocuted.

What is the capacity of the external battery (measured in mAh) you are using? Some of the external battery chargers out there simply don't have enough amperage to charge the iPad's battery correctly. And with iOS 7's stricter charging requirements for devices (seemingly mostly having to do with the Lightning cables), what may have charged it before, may not charge it now.

My external Anker battery is 10,000 mAh and it provides up to 3.7 volts. Charges my iPhone and iPad.

That's more than adequate for the iPad. Like Ralph9430 mentioned, be sure you're using a known good cable. If the cable is good, maybe contact Anker for support and see what they say:

http://www.ianker.com/support.html

I errors in my previous post. The output of my Anker battery is the same as an iPhone charger. 5 v.