I have all three of the Anker batteries, 5600mah, 8400mah and their 10000mah.

Of all three of those, personally I like the 8400 the best. It is a compromise between the larger and heavier 10000mah and the more limited 5600mah. Don't get me wrong, the 5600mah is not a bad unit at all. I use that to charge my MiFi hotspot verizon pack when there is limted coverage from ATT on my Samsung Note2 phablet. The thing I do not like about the 5600mah pack is that it only has one usb port and sometimes it is nice to be able to charge two device at the same time. Another limiting factor is the fact that it is only a 1A rating. I am not so sure what the Nexua draws when the GPS and screen is on but the 1A from the 5600mah might just might be borderline to charge your phone when you are using the gps and screen, but it might be able to maintain and conserve the internal battery.

I use a Note2 phablet a lot while at work. We do a lot of cellphone communication when we are away from the desk. It is also our only means of communication with the workers in shipping and production out on the floor. I also use a bluetooth headset that is constanly streaming MP3 music when I am not talking on the phone. So that pretty much means lots of battery usage. I wear a fanny pack with the 8400 mah pack and carry a micro usb for charging when my phone gets low instead of having to plug it into a wall and be phoneless while waiting. My note2 does requires a 2amp wall charger when the GPS, bluetooth, and display are running. The 2amp output port from the Anker 8400mah pack is capable of charging it while those apps are running.

The second 1amp usb port from the 8400mah pack is nice. I can be charging my phone while also charge my bluetooth headset at the same time. I like to stream my music from my phone to the blutooth headset during my commute back home so having a second port for me to give some kind of charge to my headset before leaving work.

So far I have yet to have any problems with any of the Anker batteries.....(knock on wood)