Got tired of the cheap portable chargers. The Anker brand came out on top of many reviews I read. I bought the Anker 20100 and so far really like it. About 39.99 on Amazon. Takes a long time (13 hrs) to get a full charge, but seems to be worth it. I charged an S4 phone to 100% from total discharge. I also charged my S6 from 22% to 100% at the same time. Only one of the 4 lights went out on the charge meter.
Brian bought the Anker 13000 and says it's well worth the price as well. Anyone needing portable power may want to look into these. A little pricey but is it really if you finally get what your looking for on an all day sit?