How many days will you be inbetween places to charge? How rough will the hike be physically? How heavy is the base weight of your pack?
5 batteries while backpacking seems a bit excessive to me, but as a “luxury item””, in backpacking terms, the extra weight is entirely up to you. Some folks carry quite a bit of extra weight just in camera gear. Others try to be as minimalist as possible. I’m thinking 1 battery 2 at the max would be the norm, even on long distance hikes. But who is to say you can’t carry more?