Is there a way to tell when the battery is actually at 100% I recently acquired an HTC Desire Z / G2, and installed Cyanogenmod 7 onto it. Something I've noticed though is that sometimes the battery drains very quickly, and sometimes it does not. Since I have a tendency to charge the battery very often, even when it has not discharged much, I get the feeling that the battery stats are not correct.

As I recall, before resetting battery stats, I should make sure the battery is at 100%. My question to that is, how can I tell if my battery is at 100%? Is it when the LED power indicator is constantly green? When Android reports as 100%?
"100%" isn't as straightforward a concept as you might think on Android. Have a read of this:

http://phandroid.com/2010/12/25/your-smartphones-battery-gauge-is-lying-to-you-and-its-not-such-a-bad-thing/