Lipo deals with 3 voltages - 3.7v/cell which is called the 'nominal' voltage - its the voltage you always see mentioned. Fully charged voltage od 4.2v/cell which is what you see with a proper lipo capable charger. The last voltage is the minimum voltage of 3.0v/cell which you should not discharge your lipo below, overdischarging can damage a lipo (swells or puffs) and make it unsafe to use anymore.


Here's a reference on lipo - http://www.rchelicopterfun.com/rc-lipo-batteries.html