RAVPower has a pretty sweet 20,100mAh battery on sale today. It sports almost every charging technology you could ask for and is very highly rated on Amazon. It charges in just 4.5 hours thanks to its QC 3.0 compatibility and boasts a USB Type-C, QC 3.0, and a 2.4A charging port. The Type-C port will charge other devices at a rate of up to 5V/3A, meaning it's capable of rapidly charging the new generation of Nexus devices. You can also use it to recharge any computer that charges with USB Type-C – like an Apple MacBook.
The power pack sells on Amazon for $59.99, but you can pick one up today for $10 less with coupon code 759XIH8U. Keep in mind you will need to supply your own USB Type-C cables and a QC 3.0 charger if you want to get the most out of the power bank. I haven't tested any of RAVPower's devices yet, but reviewers are very happy with the device, awarding it a 4.8 star rating. Pick one up for yourself by following the link below.