edit: just discovered the bitcoin tip bot.. next time.
I'm in a weird mood and bought him gold. It's a fair question... and the reason I'm willing to do it.
ulterior motive is I recognize this account has no history on these board and I'm a BTC newb and thought I'd offer what I have (Amazon Prime) to exchange into some BTC.
(PS - if anyone's looking to be a guinea pig feel free to test with a micro usb cable or something that can only be shipped free with Prime)
I have just finished replacing all my chargers with Anker chargers. I have the Anker two port car charger (http://www.amazon.com/dp/B00D82O68Y/) the four port wall charger (http://www.amazon.com/dp/B00L40YJ8O/) and the 9600mAh external battery charger (http://www.amazon.com/dp/B00DMWV3EU/).
I have also replaced every single micro USB cable with Mediabridge cables (http://www.amazon.com/dp/B004GF8TIK/).
Buy a powergen charger, I own one and its amazing. USB does NOT charge the same AC. If you see USB under battery settings you're drawing a much more limited amount of power then versus AC (plugging in a PC vs plugging in a wall). The powergen outputs much more then needed for the nexus 4, although the nexus 4 will only draw as much as needed, and make sure to get a good USB cable this one: Check this out on AMZN:
Mediabridge Hi-Speed USB 2.0 - (6 Feet) - A-Male to Micro-B Cable http://www.amazon.com/dp/B004GF8TIK/ref=cm_sw_r_an_am_ap_am_us?ie=UTF8
Not all micro USB cables are made the same, most work well, but if you buy a 99ยข one, you're going to get what you paid for (some don't even allow AC charging).
Btw, don't worry about any power problems with high mAh chargers/AMP ones. If the nexus 4 suddenly took more power then needed, it would probably explode and that would be some pretty horrible design.
Edit: another good thing about this charger is that its universal and it will split the power amount! So if you plug in two devices it will simultaneously charge them both at AC power.
edit: yes the powergen charger is considered AC charging by the nexus 4 either single or with two devices (I use mine with either the cable that came with the nexus 4 or the one I linked to)