I have been using the zippy lipos from hobby king with great luck, I use them on my Profile scale B-29 which has four of the 4S, 3000 mah lipos on board. i had to find a reasonable source since I use four batteries per flight. I got the 20C version since I am not pushing lots of amps for cl scale in profile scale.
I did have two zippy batteries give me problems with dead cell or did not charge properly, but the cost is well within reason and didn't mind having one or two batteri go bad.
I will be ordering more zippy batteries from hobby king
Fred Cronenwett