im from the philippines and i usually run in an outdoor parking lot track. we are only allowed to use electricity on big races. if i can get away with it, i always bring an extension cord and plug in an available socket, and then yank it out when the roving security guards pass by
but it is easier for me to use deans plugs and corally type connectors. for charging, i use my car battery. i park just beside the track so it is as convenient as having available AC power. this way, i dont have to lug around my heavy power supply and extension cords. plus if my car battery dies down, i have plenty of rc buddies who can jump start it
we have other great indoor and outdoor tracks that have available AC power. but i still prefer the convenience of plugs.