I drive the NC mountains fairly often. Whenever coming down I usually use "B" to slow the car rather than using the brake constantly (still have to brake fairly often). These are usually very long, steep declines (some curvey by NC mountain standards). Almost every time I have noticed my computer image showing a blank spot:



My "battery" shows it is constantly full and I can hear a difference in the engine when it seems to be "over full". Am I doing any damage to the battery or any other component (eg. computer) of the car.

 

No worries -- that's normal behavior. I've encountered it several times descending the mountains of Virginia and West Virginia. It's almost a paradox: When you let off the go-pedal, the ICE (internal combustion engine) lights and runs at an RPM that's higher than idle; the car is using the ICE to help slow itself instead of allowing more regenerative charging. When you hit a flat or uphill stretch and give it some pedal, the ICE cuts off as it tries to use the surplus charge.

Just for giggles, next time you're comin' down the mountain, take it out of B after the battery fills. I bet you'll find that once the battery gets high enough, the car will do the same thing, effectively keeping itself in B. It's all part of the car's sophisticated battery management algorithm, keeping the battery from overcharging.

The empty bar on your display is from consuming no fuel. It apparently figures that "X" miles divided by 0 gallons = 0 MPG. For some reason they changed that in 2006 (I think). In my car I'll see full bars for segments with zero fuel consumption: X/0 = ∞.