engine revs at odd times

I've noticed two cases when my ICE revs up when I wouldn't necessarily expect it to.

Case 1: Every morning I descend about 1,400' in 5 miles, meaning I often "peg" the battery meter with full green bars toward the bottom of the hill. As I'm coasting (usually around 50-55 mph), as soon as the last green battery bar lights up, I notice the engine seems to "kick on" and rev up a little. The MFD doesn't show any arrows for the ICE - just the usual blue arrows showing the battery charging. But I feel a little "lurch" and can faintly hear the engine rev up a bit. Seems like a odd time for that?

Case 2: Today I noticed that in a similar situation - coasting downhill around 50 mph - but without a full battery, just the usual blue bars somewhere in the middle. When I press the A/C button to turn it on, immediately I hear what sounds like the engine revving up. Again, no change on the MFD (blue arrows charging battery), and my foot was off the throttle.

Is this normal? If so, what's going on (just curious)? I can see maybe the ICE revving up to help out with the A/C, but I thought I remember hearing that the A/C runs off the battery. And in Case 1, why would the ICE kick up when the MFD shows a full battery?

Thanks,
Sean

 

<div class='quotetop'>QUOTE(john1701a @ Jun 15 2007, 04:18 PM) [snapback]462617[/snapback]</div>

Ah, thanks - that does make sense. What about the A/C case? Is that just a scenario where the ICE needs to help out to provide the extra juice to run the A/C?

Thanks,
Sean