Someone in here turned me onto those power meters for USB that you can get on Amazon and I have since picked up a couple What I found super fascinating was measuring how much power an iPhone can pull across different lightening cables. Not all cables are made like my a long stretch. The Apple OEM ones are among the best but among all the brands it's all over the map. Obvious,y the longer the cable the worse the flow but even among identical length cables, sometimes the amount of power the phone can suck down is almost half what another cable can do.
re:China - I too have had a couple of my battery packs taken away. One of the people that took it said that the look for a sticker that says the capacity. If it's over 10k they take it or if its unlabeled, they take it.