http://www.hobbyking.com/hobbyking/s...age_Meter.html

something like this. I cant find the one that i use, but really the same thing. Tells you how buch current, amps, bat. voltage..... You really should have one if you start trying different props. If the ESC is only good to 25 A. then you obviously dont want to pull more than say 20 A to be safe. Also, Dont pull more than what the discharge rating is on your battery. It will heat up and puff if you do. Hope this helps.