I'm looking at the external battery packs for an upcoming trip. The oft-mentioned units from Anker, Ravpower, and Jackery all seem to be suitable, but all but one model (from Ravpower) lack one feature I find useful -- passthrough/passive charging (simultaneous charging for both devices). It's one feature that is rarely mentioned by either the manufacturers or user reviews. Having to charge two devices separately, or with multiple chargers seems less convenient to me. The Patriot Fuel line has it, but I was wondering if there were any others. Also, it seems that most of what I've read indicates that these are OK (and in fact should be) as carry ons. But one Jackery user noted that they had one confiscated by the TSA, though seems like an isolated incident rather than the rule.