I'm planning to take some video footage of one of several barges that occasionally comes into our river—about once every two weeks. I'm tracking the barges on an app on my iPhone, and when I see one come into the river, I want to be able to jump in my boat and get into position in order to fly my drone (a Parrot Anafi) behind the barge. The problem is will have only about 30 minutes lead time, and it seems like my batteries don't have enough juice unless they've been recently charged. So ideally, I would be able to charge a battery while on the move. Can anyone recommend a portable charger or suggest some other strategy to keep my batteries ready to go?