Strange Engine Cycle on a Hill

Very normal. The engine is being cycled on-off by the electric motor to use up excess charge from your downhill. Smart car, but it does do 'weird' things, all to keep that battery in a narrow range of charge, allowing an 8-year/100,000 mile warranty (longer in some stricter emissions states).

Enjoy!

Curt.

 

<div class='quotetop'>QUOTE(BK_14 @ Apr 11 2006, 05:26 PM) [snapback]238221[/snapback]</div>

This is apparently normal. It has been reported by many people here. Current theory is that the car is trying to drain off excess charge from the battery. I bet your Energy screen shows all green bars on the battery icon when this happens.

The Prius tries to keep the battery state of charge (SOC) between 20% and 80% of capacity. Regenerative braking down long steep hill most likely charges the battery beyond 80% and the car repeated starts the engine to drain off the excess charge.

That's the opinion here anyhow.

 

My guess is that spinning up the engine is the only way the car can bleed off excess power if you're not going to start moving. The car has no way of knowing how long you'll stay stopped, so it has to do something.

I suspect they can't simply spin it without feeding it fuel, otherwise they'd do so.

Hey...maybe the car should just turn the radio up full blast to use up some power!

 

That's what I was curious about - would it take gas then I assume when the engine engages? Not use the excess electricity? Either way I don't think it affects it too much...

<div class='quotetop'>QUOTE(Rick Auricchio @ Apr 11 2006, 03:43 PM) [snapback]238268[/snapback]</div>

 

Now that I think of it, the car may be spinning the engine without fuel. That would burn off the power, and the engine often can spin without fuel (as when we're over 42mph and running on electricity alone).

When it happens again, check whether the display shows any fuel use (even though it isn't instantaneous, it'll show 99.9mpg if there's no fuel being used.)