Lithium-Ion?????
That's 30 Amp-hours, which is a lot. What is the voltage? The absolute limit is 160 wh (Watt-Hours). Voltage x Amp-Hours = Watt-Hours.
...In most cases, up to two larger lithium batteries (more than 100 watt hours, but not exceeding 160 watt hours) are permitted in carry-on baggage if the terminals are properly covered or insulated. If you are traveling with a battery-operated mobility device, please see our Special Travel Needs section....
For reference, I want to buy one of the new E-Bike 500 wh battery packs that are just now available in the UK, but there's no way to get one back to the US on a plane (even shippers like FedEx won't touch the thing). The current 396 wh batteries are 36 volts
and only 11 ah, so I strongly suspect that your 30 ah battery is a bit much unless it's a much-lower-voltage unit than I'm talking about. For example, the Anker unit mentioned above would be ok. Specs:
Capacity :26800mAh
Output :5V / 4A (total)
So 134 wh
Again, the above discussion pertains to Lithium-Ion batteries.