I'd take them back where you bought them - thats not right. I have a EFlite MCX heli and I've used the lipo thatcame with it 100s of times. I'm just getting started with CX2, but its lipo has already been charged over 10times.

Take the charger with you, have them check it out - it could be charger is bad.

You should be getting a lot more charges than what you're seeing.