Hey all. .a couple weeks ago I was thinking "how can I charge my batteries while out & about " Thinking that I. Any put everything on the car. Phone, iPad, RC, batteries. Realized I have this Power Pack thing meant to Jump start a car, but also has an air compressor for tires AND- a 110 plug outlet as well as a USB port. Cool. So I started carrying it in the car and when I pull a battery (and let it cool) I can now charge it while flying my other batteries and lock up the car. It does work- but has its limitations. Doesn't like heat. On hot days can't close up the car & leave it. Not safe anyway. And I'm finding that when it gets to about 50% - after charging 3-4 P3 batteries, it stops charging and give off a warning alarm. So, long way around, but- are any of you using something better?? I know there are Inverter batteries designed to plug in professional camera strobes in the field. More robust than my $100 car jump start thing. What have you all come up with??