+1 on the Galaxy S5 with extra batteries. That's what I use. Plus, if you're out of a service area, which you likely will be, put it in airplane mode. It's shocking how long the charge will last in airplane mode. My last outing was roughly 48 hours from the time I unplugged it from the car charger to the time I plugged it back in and it still had 75% charge. I had been using it a lot for pictures as well.
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The journey is more important than the destination.