OK first off, I want to state that this was NOT an uncontrolled "runaway" episode, but it was something unusual. I was at a stoplight today and unexpectedly, I had a a very high surge in RPM's with no input from me. To add, the battery was full, and the car had been running for more then fifteen minutes in almost 70 degree weather. So, It was not the car "recharging" itself. It was way higher than usual for that. Also, I've had my Prius new off the lot since 2004, so I've gotten to know the cars little idiosyncrasies and this was a new one. Like I said before when it revved, I was at a stoplight. I even released pressure off the brake pedal out of curiosity and it didn't move. The whole episode lasted about 10 seconds and took about 3-5 seconds to come out of it. So what could have caused this? I have no concerns out of my curiosity, but it's just that. I'm curious.
When a Prius HV battery has a very high State of Charge (SoC), the Prius will work hard to bring the SoC back to more normal levels. If the Prius is standing still, it can't do much to help, so it burns of excess charge by spinning the engine with MG1. The engine is not running; it is used as an air pump to load MG1 and burn off charge. In this situation, generally the engine will race for a few seconds, stop, race again, stop, and so on until the SoC is reduced to an acceptable level. Tom
Tom, Your answer gave me another question. Being an '04, does this event say anything about the long term health of the battery? One would assume that if it holds a full charge and then some, that the battery is in great shape. But you know what they say about assuming.
it really doesn't say anything about the long term health of the battery, but, odds are, your battery is in excellent condition based on long term statistics.
This is normal behavior for a good battery, so we can't really infer anything from it. As bisco stated, HV battery problems are rare. Tom
Thanks again for the info guys. It's feedback from people like you that make it a pleasure to come to PriusChat.
