I recently bought a powerbank that has two USB outlets. It's great for charging my phone and iPad. Is it possible to charge my MacBook Air from the powerbank? If it's not possible to do this "out of the box", would it be possible to build or buy something that would enable me to do this?
Yes, The answer is positive. The power bank capable to charge a laptop needs to supply not only the USB standard charging port but also (or only) a DC output port, or a build-in power inverter with an AC outlet.
Here i collect some power bank that can charge laptop:
1.Anker® Astro Pro2 Multi-Voltage Portable Charger – 20000mAh Multi-Voltage 5V 12V 16V 19V for iPad Air, Mini, iPhone, Samsung Galaxy, Note, HP, Dell, Acer, Asus, Toshiba Netbooks
2.RAVPower® Xtreme 3-Port Portable External Battery Charger with Multi-Voltage 23000mAh Multi-Voltage 9V/12V/16V/19V/20V – for Apple Macbook, UltraBook, Digital Cameras, Surface Tablets,Asus Tablets and more
3.Poweradd™ Pilot Pro Monster Capacity Multi-Voltage Portable Charger – 32000mAh Multi-Voltage 5V 9V 12V 16V 19V 20V for Tablet PC, Netbooks, Notebooks, Laptops, Smart Phones
4.BiXPower 153 Wh (42500mAh) Super High Capacity 12V & 19V External Rechargeable Battery Pack – BiXPower BP160 Made with high quality Panasonic Li-ion battery cells. Compact size can easily fit into a laptop/notebook carry bag
5.Energizer XP18000AB Universal Power Adapter with External Battery for Tablets/Laptops/Netbooks/Smartphones
Energizer XP18000AB Universal Power Adapter with External Battery for Tablets/Laptops/Netbooks/Smartphones
6.Qi-Infinity™ Powergrid External Battery Pack/High Capacity Power Bank charger – 34200mAh For Laptops, Notebooks, Netbooks, Tablets and Smart Phones
7.Lizone® Extra Pro Super Capacity Portable External Battery Charger 40000mAh For Apple Books, HP, IBM Lenovo, Tablets, Smartphones and more
8.Intocircuit® Power Castle PC26000 External Battery Pack/High Capacity Power Bank charger – 26000mAh 12 Connectors for Laptops, 10 Connectors for Phones and Tablets, AC Adapter Included
There are power banks available with various plug in connectors for laptops, but they cost around 15,000. I have seen one on ebay india, and the ad says that they’ve even sold 29 units. These are not marketed by laptop manufacturers so I am not sure what your laptop warranty status will be if you purchase one of these banks and use it charge your laptop. Most laptops charges through its adapter only. Powerbanks on the other hand have only usb 2 output interface. Replacing laptop batteries with Extra cell batteries available in the market can help. One desi jugaad is using a UPS to charge a lappy but it wont make it handy and portable.
If your Powerbank has a output for 14.5 Volts (DC) then yes, you can use it with magsafe plug. But not if it has output of 5 Volt (typical output).
There are ways to do it, but would require 5-15 Volt converter including USB to magsafe cable and plug.
There are also car chargers for your MacBook.
Then there is this thing, but at ridiculous cost of $300 and up.
Depending on your GPS location you could consider one of those.
This looks like the best option for changing MBP and MBA at the moment (Aug 2015)
No. A powerbank is a battery device designed to charge small devices through the USB ports, but not provide the wattage necessary for charging a MacBook's battery.