It's always good to have battery back ups

. I particularly like the smaller one so they're either hold. And can fit in a purse or your briefcase/laptop bag. This one also has an LED light two quick clicks turns it on and off. It comes with a universal charging cord that is not for iPhones, so if you have an iPhone you may want to put a charging cord with it. 
These are also great to have when you're traveling you never know when you're not gonna be around an outlet plug