RAVPower 16750mAh Power Pack
Source
I have had a lot of USB charging packs over the years. Most of them loose their charge fairly quickly and have to be replaced. I needed a new charger as my old ones no longer held a charge and ended up throwing them both out.
This time around I wanted one with smart charging. Smart charging allows it to automatically adjust and optimize it's charging current based on the device connected. I also wanted a charge that can charge an iPhone and iPad at full speed in both ports at the same time. The RavPower charge can do up to 2.4A per port, high enough to fully speed charge any iPad device.
16,750mAh can charge an iPhone about 5-6 times and can do a full charge on an iPad.
The device is a little larger than a deck of cards and is easy to carry around in your pocket or purse.
I am very happy with it, and would get another if it loses it charge, which tends to happen after a few years.