How to get prius to shut engine off more often (use battery to propel)?

Are you doing it when the car is fully warmed up? Unless your HV battery State of Charge is really low, the engine should shut off when you let off the accelerator going to a stop (unless you're doing highway speeds).

 

If the ICE isn’t shutting down on coast after you have been driving for about 10-15 min, come to a complete stop (where convenient and safe) leaving the car in READY and wait 10 seconds. The hybrid control then stops the ICE. After this, the ICE should stop running when coasting to a stop.

Try that and see how it goes.

 

What is causing this?

 

It is not caused by anything, it is just what it does. Goes from stage 3a/3b -> stage 4.

See the 5 stages of Prius warm up link in my sig for full details.

I should add, if you are using heat/AC, it can also keep the ICE running until the car is fully warmed up.

 

I mean, why would shutting down change it?

 

Ops issue is probably his hybrid battery is getting tired. Mine started doing that not shutting off along with quick tank to purple before I Prolonged it. Back to normal now.

Op should start watching his battery behavior on the mfd closely. He may be in Stage 1 of battery death.

 

how many miles on the '08? ed is probably right. 12 volt could also be an issue.

 

Sorry if I was not clear, the car itself is not powered off, it stays in READY. You just wait for the ICE to stop after the car is at a complete halt.

As to why waiting for the car to stop the ICE, the only explanation I have read is that the control system does some kind of calibration and until it does this calibration, it can't ran as economically as it is possible.

If the ICE still does not shut down of its own accord, then the next guess would be as edthefox5 guessed, a tired HV battery. Especially if the SoC meter goes down to purple and back up to green very quickly.

[EDIT] Re-worded post #3 to try and be a bit more clear.

 

OP should read about the warm-up stages in @dolj post.
You have to come to a full stop to get into the last stage.

 

you mean if you start a cold prius and go out on the highway on a summer day, and get off the highway, the engine won't shut off until you come to a stop?

 

I believe that is correct, but I just drive the vehicle.

 

huh, i've never noticed it in 14 years, but i can be oblivious.

 

For some reason, when a Prius is new, you don't notice it so much. Seems to be quieter and smoother shutoff. I had my Prius for a few years, before I noticed it, then thought something was wrong with it until I found out about the 5 stages.

It's like that scratch that is there that you never notice, then when you notice it, you can't not see it.