Has anyone else experienced this? I was going down a long steep hill from Wayne PA to King of Prussia PA and got to the rare max battery charge possible. I was in eco mode. I accelerated from a complete stop using only the electric motor only, but the acceleration seemed much better than I've ever experienced using only the electric motor. I believe that I actually went past the line where the gas engine usually kicks in, but this time the gas engine didn't kick in and it was all electric motor.
It would have been warm from a full charge, and being fully charged it would have been (temporarily) a "higher" HV pack. It's like fresh batteries in a flashlight, brighter for awhile.
Normally the engine will kick in if the Hybrid Synergy Indicator bar goes past the median mark, no exceptions. But I've noticed once or twice, after coming down Mount Seymour, with the pack full-to-the-gills, it would keep the engine off, even though I was maybe 1/4" beyond that median on the display.
This. The prius doens't like having a "full" battery, and tries to discharge it to normal levels as fast as reasonably possible. So whereas you'll normally engage the ICE halfway up the eco bar of the HSI, in this situation, it will take even more acceleration before it switches off of battery power.
At that charge, or knowing ahead of time of a downhill, I always max out the AC so it doesn’t charge past 75% on techstream. Your battery pack has a greater chance to bulge at higher temps, avoid that.
On a "normal" hill you can't avoid it. In my experience it takes only 500 ft of descent and battery is full then you are left with engine braking and brakes. This kind of driving burns through the brakes rather quickly as the engine, even when annoyingly revving to the max, does not brake that much. I had to change my brakes at 75,000 miles. One other thing, if the battery temp goes past 50°C (122°F) it will not charge and discharge that aggressively, so sometimes even when the battery is at full 8 bars the car may not behave as OP describes. The worst you can do is to shut down the car immediately as battery gets to full 8 bars on nice hot summer day. I tried it once, and when after one hour I restarted the car it was working like there is no battery and battery temp was at 60° C
