Good point, my satchel I use for work and wandering the city has a few support items for my phone: wall charger and usb cable, external battery, and aloksak for severe weather. I have an Iphone which burns through battery at a ridiculous pace when its used a lot, but by turning off different functions (data, location services, putting in airplane mode) when I'm not using them, I can extend the battery for days. I do this when I'm camping since I don't need to be connected, but I might want to be. In an emergency I would probably do the same thing. Data and location off to conserve battery or turn it to airplane mode and just check for messages every half-hour or so.