Galaxy S8 Battery Case, $20 with code SH688DTB | S8 Plus Battery Case, $20 with code WKZ5XHCU

The Galaxy S8 and S8 Plus get pretty good battery life, but it could always be better. These battery cases from ZeroLemon effectively double your smartphone’s runtime for a measly $20; just be sure to choose the right model, and note the promo codes below.