I bought this for my daughter for XMAS. It's small and puts out 5v by 2.4amps x 2 ports (4.8amps total). Basically, can charge a new iPhone from dead like 7 times, or run a GPS all day long. And it's small in size. You'll need that 2.0+ amps for charging newer phones and tablets. The older USB chargers only put out about 0.5 amps
My daughter uses it when she is going to concerts or other places where access to either a 12v or 120v charging source is not available.
Perfect for those long car shows or travel in the Packard as well since the rear seat does not have a 12v source.
Probably the cheapest/longest power option I know of and has lots of other uses outside of the car. We have taken similar ones camping/hiking also and they are a godsend.
http://www.amazon.com/Compact-20000mAh-Portable-Anker-PowerCore/dp/B00X5RV14Y/ref=sr_1_1?ie=UTF8&qid=1454958046&sr=8-1&keywords=ankerThis Post was from: https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?post_id=171950