My 2001 Prius makes this sound when the engine is running. All the battery lights are on all the time, I think it needs a new HV battery but I'm not sure if it's worth it. Perhaps the other battery is faulty I really don't know. All the engine lights are on and if the brake light comes on it starts shaking or the power steering fails or it just completely shuts off on the road no lights no power steering nothing. When that happens I use a battery booster that I keep in my trunk to get it going again but it's really dangerous to drive now.
Anyone had this issue or know what the trouble is exactly? Everytime I take it to a mechanic or HV specialist they have a different conclusion.