I have been using an Anker Powercore which has been great. Supports through charging which is a plus… you can charge the battery, whilst charging a device through the battery if that makes sense. Pick one for your budget and size limit. I went bigger than I thought I would need.
Not bikepacking, but for travelling I have two of the Xiaomi packs. A 10,000mah and a 16,000 mah. 16 is great but pretty heavy. I got mine overseas but this Aussie site also seems to have them. http://www.mushtato.com.au/xiaomi-45/mi-power-bank-46/
Two outlet usb ports. Can charge and charge (?) at the same time.
tbh, i reckon i’d prefer something pretty light & portable as if i’m in my car i can always charge my phone off my ciggie lighter, so something that’ll do similar for in the pannier or whatever would be good. how much juice do high lumen lights need? just got a 760 lumen clip on as no more dynamo…
+1 for Xiaomi. Great quality. Best value. Great deals show up frequently on the ozbargain web site. I also believe there are reviews online that tell you which chargers are really pass through if that is important to you