Small suggestion:
When you look for a field charger, try to get one that has both the normal crocodile connections (to connect straight to a 12v battery) but also try to get one cable for it that have a cigarette lighter plug.
I have a Futaba C-2000 charger and it's perfect to hook up the radio + plane to the charger and then plug it into the cigarette lighter outlet inside the car.
This way I charge my stuff while driving to the field and never have to "pop the hood" to access the car 12v battery...Very convinient!