When traveling long distance it's always handy having extra phone battery without having to plug your phone into a wall electrical socket using a multiport wall charger. Extra charge is particularly useful  if you're a heavy phone user or want to help others charge their phones.
If your smartphone doesn't hold charge for very long carrying a powerbank is certainly the best way to extend the life of your phone!
Of course, all powerbanks are not created equal so it's worth looking for a fast charging power bank like the upgraded version of the Anker PowerCore Speed 20000 that can increase your recharge speed charging capacity.
To give you an idea of how much storage capacity the PowerCore Speed's 20000mAh battery holds, it can recharge a Samsung Galaxy Note 8 phone three times over, an Amazon Kindle e-reader three times over and an LG G7 phone two times over.
The Anker PowerCore Speed 20000 has a grip, ergonomic finish that makes holding it in the hand comfortable. The power button has an led clock-like design that shows the battery level per led.
While the Anker PowerCore Speed 20000 is heavier and bulkier (369 grams) than the PowerCore II 10,000mAh powerbank,  the PowerCore Speed 20000 does provide twice the battery storage as well as a 12W (5V/2.4A) output port and an 18W PowerIQ 2.0 output port that supports Qualcomm 3.0 quick charge (5-8V/3A, 8-10V/2.4A and 10-12V/2A) port so you can charge two devices at the same time.
Having a Qualcomm quick charge port is neat but keep in mind that non quick charge compatible devices will charge at normal speed via the Qualcomm quick charge port. The PowerCore Speed 20000 measures 17cm, 6.2cm wide and 2.2cm thick.
 It's also worth keeping in mind whether your phone supports Qualcomm quick charge because the Anker PowerCore Speed 20000 does not provide fast charging for the Zenfone 3 (ZE552KL).
 Many people believe the Zenfone 3 supports Qualcomm quick charge when in fact the Zenfone 3 does not support Qualcomm quick charge even though its chipset supports it. The deluxe version, Zenfone 3 Deluxe does support Qualcomm quick charge.
Neither the Nexus 6P and Nexus 5X support fast charging standard, so you won't get fast recharging speeds using the Anker PowerCore Speed 20000. Both the Nexus 6P and Nexus 5X use the new USB-C standard to charge at a rate of 15W (equivalent to 5V x 3A). Also, keep in mind that the Anker PowerCore Speed 20000 does nor provide charge for low input devices below 50mA.
The upgraded version of the Anker PowerCore Speed 20000 uses a 18W PowerIQ input port that supports Quick Charge 3.0 (5V/ 2A, 9V/2A and 12V/1.5A) as opposed to the 30W Power Delivery input/output fitted to the standard PowerCore Speed 20000 that makes charging and recharging  extremely fast (only 4 hours to recharge when using a 30W wall charger).
The upgraded version of the PowerCore Speed 20000 takes 6 hours to recharge and also gains an extra USB-A output.
Bear in mind though, that you have to use a quick-charge compatible wall charger with the upgraded version of the Anker PowerCore Speed 20000 otherwise recharging the powerbank takes 10 hours.