This Anker black Astro E1 ultra compact portable charger is down to $13.19 on Amazon. It normally sells around $17 and the other colors are selling for $20 right now.

This charger is the size of a candy bar but has 6700mAh, which means it's got enough power to fully charge a Galaxy S8.

Features include:

  • Exclusive PowerIQ Technology: Detects your device to deliver its fastest possible charge speed up to 2 amps. Does not support Qualcomm Quick Charge.
  • Add over two full charges to an iPhone 7 or 6s or at least one full charge to a 7 Plus, Galaxy S8, Nexus 5 or other smartphone
  • Fits perfectly in your pocket. Recharges in 5.5 hours with a 1A adapter (not included) and the included Micro USB cable.

It has an 18-month warranty from Anker. Users give it 4.5 stars based on 539 reviews.

You can use the included micro USB cable or upgrade to a 3-foot cable from Anker for $5.

See on Amazon