Anker's excellent Anker PowerCore Speed 20000 usually costs $56 on Amazon, but today it's a Gold Box deal on sale for $42. It can fully recharge an iPhone 7 seven times, and can charge two USB devices at once. It can even charge the power-hungry Nintendo Switch. I gave one to my nephew and he said it can charge his Switch even while he's playing it. (If you're looking for smaller less expensive battery that will charge the Switch, consider the $29 Anker PowerCore 13000.)
