guver's tables are very useful. Don't let the slight differences between the three charts concern you. In reality, all three are telling you the same thing, which is that you can tell the state of charge of a lipo by simply measuring its voltage.

4.2V per cell = fully charged
3.5V-3.7V per cell = fully DIScharged

And if it isn't obvious by now, a wattmeter is an essential tool for electric pilots.

- Jeff