I will be staying off grid with friends for several weeks. I need your real world experience with portable solar panels, to keep an iPad charged. Their system barely handles their needs so I want to brin my own. It needs to be small enough to pack in. I already have some battery banks so I just need a solar panel with a USB port. My budget requires me to be under $75, but hope to be closer to $50. I have been reading reviews and specs, but what I really need is your personal experience both good and bad, to help narrow the field. I only have about a week to do this so bonus if it is Amazon Prime. How big a panel do I really need? Specifically for an IPad? How durable are they? Brands that held up, and brands that fell apart. Help me narrow the field, please. Thank you in advance for your time and attention regarding this matter.