Personally I use a 30Ah external battery with a braided Micro-USB / USB-C / Lightning cable to charge anything.
Discussion
That's a very good option for situations, but part of vacation is summiting a fairly difficult mountain. I'm not wanting to carry a 30Ah battery... LOL
I do have a 10Ah battery pack that I'll keep with me on the other leg of my vacation as I'll be jumping in between 5 vehicles and not all of them will have a usbc cable handy (darn iPhone users!) so I want to make sure I've got something to help keep the battery topped u when using navigation and making calls.