I am curious: I have never seen the battery indicator of the hybrid batter at 100%. It appears to be at about 80% is that normal? When or how can it reach the 100% mark?

 

I've read the battery does not fully charge or discharge to extend battery life. I've seen the bars all the way at the top of the scale after descending a long grade but never on flat ground.

 

Mine has had the indicators at 100% two times that I have noticed...both coming down the Santa Cruz (CA) freeway to San Jose. It was basically a steady long downhill slope after having a good change at the top of the hill so the regenerative braking had a lot of fun those days.

 

For good reason you only see 100% charged on the scale after a period of extended brake regeneration. If the ICE was always charging the battery to (scale) max, then regenerative braking would not be useful very often.

 

As TheDosDog mentioned, the battery SOC(state of charge) is well controlled with in a certain level to extend battery life.
Please note that it is still about 80% SOC when you see 8 full battery bars, not 100% SOC.
Following chart is derived from very good Toyota Hybrid System presentation...
http://john1701a.com/prius/presentat...ntation_01.htm

Ken@Japan