So I'm considering buying a power bank to charge my phone on long trips so I can run my maps and stuff for the entire week and make calls if I have too. There are sooooo many options on Amazon. I'm wondering what is the best one out there that has a high capacity (10000+ mah, 20000 preferred) and also low weight for about 50 bucks or less. Charging a Samsung Galaxy S8. What do you use?