Yet another engine start condition!

It may not be actually running the engine, but rather just spinning it (no fuel & spark) to drain off the excess energy.

 

I think you are right. This happened to me once. I also go downhill over the first half mile of my drive. One time, the engine started. I wasnt using the heater and I am always careful not to start the engine through throttle input. However, when it happened that day, I figured I wasn't being careful and gave it too much throttle (even though I coast much of the way down the hill).

Your experience sounds like it explains my engine start last week that I couldn't explain. That may also explain why my EV range continues to drop each morning. It's possible it assumes I regen, on average, X amount, so it leaves a little buffer? I have my Kill-A-Watt on tonight. I'll check tomorrow to see if it's taking less charge than normal. I may be able to get a SoC % tomorrow morning via Torque. I'll report back tomorrow morning.

 

I can't answer your question, but, the more I learn about how the "Hybrid Synergy Drive" works, the more amazed I am at how complicated it is!

 

I don't think it would leave the battery slightly uncharged as a buffer. I think the EV range drops b/c it is counting all the electricity it regens going downhill and burns off using the engine as electricity consumed, so your watts/mile goes up, lowering your EV range.

 

Hmm.. I guess leaving a buffer wouldn't be the best thing to do from an technical/engineering standpoint. But I've only had the engine start on me once in this unexplained manner. However, my EV range has been going down almost every day. I still make it to work on all EV with anywhere between 0.6 and 1.4 EV miles though.

In any case, I'll post my Kill-A-Watt reading tomorrow. The one time I used Torque, my SoC on a full charge was 85.1%. So we can compare that to tomorrow's reading.

 

because its a plugin your leaving your home with a full battery..
so going downhill just after that you wil have no more room for energy storage.
its the same with the non plugin prius after a long downhill regen the ice wil bleed of energy

 

This is the same behavior with the regular noplug Prius. When the battery is full and the regen brake (MG2) continue to pump more electricity into it, MG1 will spin the gas engine to dump the excess electricity.

 

maybe you should leave home with a partially charged battery. then you can get some 'free' electricity.

 

This is a similar strategy that many Leaf owners use... If you don't need max range, then charge the Leaf's battery to just 80% (automatically) or 90% (manually end charging). This way you get the benefits of regen coasting and braking. If the car begins a trip with a 100% charge, then only the conventional brakes are used to slow the car when the brake pedal is pushed, and there is no little or no coasting regen. You lose the energy capture opportunity during this time, but it protects the battery. Once the state of charge drops down a bit, then you get the regen benefits again.

Note: A 100% battery charge on the Leaf really is a 100% state of charge. A "full" charge on a PiP may be less than 100%.

 

Last night's charge on the Kill-A-Watt was 3.11kWh. When I left my home, I was seeing 85.1% SoC. Its maybe a quarter mile out of my neighborhood, onto the street, then to the first stop sign. I watched the SoC but after dropping to somewhere around 83%, it was only able to regen back to 84.3%. I guess if I was really trying, I may be able to regen back to 85.1%? maybe more, triggering the ICE?

Anyway, on the way to work, I used Siri on my iPhone 4S to log EV range remaining and SoC (just tell Siri "take note 12.1 and 85.1" and it'll create a note with "12.1 and 85.1", pretty cool).

I'm not sure if this data is really applicable to anyone else since I don't know why my car shows 12.1 miles of a full charge versus 13.3 or even 11.1 for some other people (or even myself at other times).

EV Miles Remaining ... SoC

12.1 ... 85.1% (fresh charge)
10.3 ... 76.1%
10.2 ... 75.7%
9.7 ... 72.5%
9.0 ... 69.0%
8.0 ... 63.9%
7.0 ... 59.2%
6.0 ... 53.7%
5.8 ... 52.9%
4.8 ... 48.2%
4.1 ... 44.3%
3.0 ... 38.4%
2.2 ... 34.9%
2.0 ... 34.1% (parked car)

On a side note, I made it to work today with the most amount of EV miles remaining today, 2.0 (I usually see anywhere from 1.4 to 0.6).

This was all city, no freeway, maybe half 40-45 MPH and half 45-50 MPH. The last 4-5 miles of my drive were pretty smooth, not too many red lights, very little traffic. This also includes an elevation drop of about 400 feet (mostly within the first 6 miles, I would say). Total trip to work is 13.3 miles.

 

The depth of discharge is 52% (85.1 - 34.1). You went 13.3 miles with it. You are getting good with it.

The 3.11 kWh charge was to fill up yesterday's drive. It wouldn't be useful to apply it to this morning drive.

 

Hmm.. thats right.. I never gave it much thought. I'll try to plug my Kill-A-Watt in at work. My charge timer is set for 3PM so I have time to get out there.

 

Or you could try putting the car in "B" going down the hill. It is my understanding that "B" provides engine braking and less regen. I use it all the time for long down hill runs when I don't want to ride the brake.

 

B mode in demo PiP increased the level of regen without any throttle pedal applied. It did not run the ICE to do it.

 

Are you sure about this and how do you know the ICE isn't being used? My understanding is that the ICE isn't really "run"/burning gas when it is used for engine braking in B mode. Instead, the engine valves are just left closed like a regular ICE, so air pumping losses slow the engine rotation and cause it to brake.

Another possibility is that the Plug-in can brake harder with regenerative brakes since the battery can accept more power than a Liftback battery. In which case, it might be able to simulate engine braking with regen brakes, until the battery fills. If so, then once the battery is full, the Plug-in would have to switch to real engine braking. Was this test with a full battery?

 

Some owners who live on large mountains manually stop the charge even lower than 80% - 60-70% has been used by at least one owner.

"100%" on the LEAF is around 94% full. "80%" on the LEAF is around 75% full.

 

the thing is, if you fully charge, you're paying for the electricity. using b mode or any other method going downhill from your start isn't really giving you any advantage. once you figure out how much charge you're picking up on the down hill leg by experimentation, like oilfreedom and drees said, you'll know how much charge to put in it before leaving, saving yourself some dough and the grid a bit of juice.

 

My Kill-A-Watt read 2.77 kWh when I left work.

So that makes it 208 Wh/mile? I guess the 400 foot elevation drop helped a bit too, eh?

 

Does that include additional miles going out for lunch?