I have a Naztech PB15000 and ordered a Intocircuit Power Castle 32000mAh and Anker Astro E7 Ultra-High Capacity 25600mAh (for powering my recorder)
You can never have too much battery power, that's for sure. The most frustrating thing in the world is to have to mess around with batteries to get through a whole show or to make it to the end of the weekend at a festival. Over the years, I've just kept my eyes open for really good battery deals and jumped on them even though I might not be in the market. It's paid off in that I have an abundance of juice to get me through any situation, even with multiple recording rigs.