answer:I would get a battery pack, they have become very inexpensive. You charge the battery using a USB cable from the wall or your computer. And you charge your phone from the battery with a USB cable, too. They have little $5.00US batteries at my local computer store, they’re at the cash register for impulse purchases like candy at the grocery store. I bought one and I’m happy with it. It almost charges my phone once. Solar is much more expensive, and I don’t think worth the trouble unless you are traveling in the wilderness without AC power. I don’t know about hand-cranked models. It is very easy to judge the size of the backup and see what you get for your money. Battery capacity is measured in milliampere hours (mAh). For example, the iPhone 5c has a 1,507 mAh battery. So a 3,000 mAh backup would charge an iPhone 5c about twice. A 10,000 mAh battery would charge the phone six times. If you are charging a larger device like a tablet, make sure the battery has a charging output of 2 amps (2,000 milliamps). Tablets and some bigger phones need 2 amps.