Hello all! I have a 2008 Prius, and lately I've been noticing that when I go down hills, or when I start braking from above 60kph, the car sounds like a helicopter. When going downhill at speeds above 60kph, the sound stays until you start accelerating, but when braking, it is only there for a second or two and then is gone. I'm thus assuming that it has something to do with regen braking. I tried hard braking, and it helped for a couple minutes, but then it came back again. I've searched all over trying to find answers, but with no luck. Any ideas on what it could be?
Weird sounds and how people describe them on here are near impossible to diagnose. Even worse when they try to make a recording of it. Let's focus on way easier stuff: Is anything wrong with your Prius other than the noise? How many miles? How is the MPG? Is regen data on your screen different than usual? Are you using original battery? Are you using original brakes?
Hard braking uses your hydraulic brakes; normal braking uses regen to turn the transaxle's motor generator to slow you. Hydraulic braking takes over from regen when moving slower than ~6 mph. If your hybrid battery has low capacity it is conceivable that it maxs out quickly and the hybrid system goes to engine braking which is much louder. Watching the state of charge and amps into the hv battery would help diagnose.
