We've seen some great batteries from Just Mobile, and its new Gum Max Duo ($130) adheres to the same design language while boasting the company's largest cell to date: 11,200mAh. Like the rest of the current Gum lineup, this one wraps two pieces of aluminum around a black plastic core. The biggest difference compared to the past Gum Max model is the new version has two USB outputs. One supports Retina iPad charging at 2.4A, while the other handles…
