First time I experience the engine rpms hanging and not coming down as fast as they should. (As if it was in B mode but not regen braking) Today was really hot and I could tell the hybrid battery was hot since the fan was running. This only lasted for a few minutes then went back to normal. I never really experienced this but it was quite hot today and I was pushing the car more than usual since I was late.
If you had a scan tool, it would be interesting to know if it showed the engine twirling without fuel. When that happens, it's being used to twirl off a bit of excess energy. The energy involved is just wasted, of course, so this is less efficient than just keeping the energy in the battery and using it, say, for your next acceleration. So the car needs a pretty good reason to do this. Extra-high battery temperature could be a good reason. I think I have read that the NiMH discharge reaction is endothermic: using some energy out of the battery actually cools it from the inside. (There's a limit, of course, because a high-enough current likely heats the battery more than the endothermic reaction cools it, but Toyota may have worked out a usable window of lower currents where the cooling effect might predominate.) I don't think I have ever caught my 2010 doing this exact thing, but there have been other posts here reporting it.
That's what I'm thinking. The car was sitting in the sun, the battery was almost full and I accelerated pretty hard a few moments after starting it. With the hot outside temperatures, I think these were all contributing factors and the computer was trying to discharge the battery somehow but I just scanned it with my Techstream and health report was fine.
The health report is going to be fine unless there is some problem. The car normally doing what it's programmed to normally do in a certain situation usually isn't reported as a problem.
It is also possible the battery was so hot the system reduced its ability to supply power causing your engine to rev higher to move the car. It would also keep the engine running even when slowing to instantly supply engine power. I have had the opposite situation when the battery becomes overcharged due to an overnight change in the weather followed by my normal one mile downhill regen. In those cases the car will accelerate hard on battery alone and stay on battery to 35 or 40 without effort.
