I noted on the last trip to Phoenix that while in cruise going down hill, holding the lever down (cost/set) that the battery was getting a large charge, just as though you had your foot on the brake. Didn't see anything in the OM about it.
That happens any time you coast, and the higher the speed, the higher the amount of charge.
To simulate "engine drag" that you would find in a conventional car, the regenerative brakes activate slightly any time you coast. The solution to this is to gently press on the gas pedal just enough to eliminate the HSI showing a line in either the REGEN region or the ECO region.