For a long time I held off from getting a P3 or Inspire 1 due to having problems figuring out how to safely field charge their batteries without draining my car's battery due to the capacity of the flight LiPo batteries. I finally settled on the Goal Zero Yeti 400 and I can report that after a few months of use it is a great solution. http://www.amazon.com/Goal-Zero-230...=UTF8&qid=1439683464&sr=8-1&keywords=yeti+400 I use it with the P3 and 6 flight batteries plus the controller and the tablet; so far I have flown almost 8hrs straight and it has kept everything charged with no problems. I have yet to even crack 30% discharged in a days flying. I even use it now to top off my DSLR batteries, cell phone, laptop, and anything else I can throw at it. I hardly use my car's lighter sockets these days. My favorite feature is that it can also be recharged by your car's charging system so what I did was wired up a relay so that it does not charge when the car is off and automatically charges when the car is running. With this setup I can easily complete up to 10 jobs a day without running out of battery juice.