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Discussion Starter #1
The other day I was trying to explain to my wife how to read the display, when is the battery moving the wheels, when is the ICE charging the battery, etc, when I noticed a combination that does not make sense (to me): I often see the pink (salmon?) lines from the ICE both to the wheels and to the electric motor, and at the same time there are yellow (orange?) lines from the electric motor to the wheels. And there are no lines at all to and from the battery.
That means that the ICE is powering the wheels and the electric motor, and that the electric motor is also powering the wheels :!:

Is that a bug or a feature :?:

Is seems wasteful to me :!:
 

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Thanks to the plantary gears it is possible for both tht ICE and electric motor to power the wheels at the same time. Also, the ICE can power the motor directly without the battery.
 

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There is a very good description at Graham's site:

http://home.earthlink.net/~graham1/MyToyotaPrius/PriusFrames.htm

ICE Power Only
Occasionally (in my experience), the display at right appears showing no power flowing either to or from the battery and all power from the ICE being used to move the car. Orange arrows represent mechanical power flowing from the ICE both directly to the wheels and to the motor/generators via the PSD. One motor/generator (MG1?) converts mechanical energy into electrical energy which is used by the other motor/generator (MG2?) to help drive the wheels. Mechanical power from the motor/generator to the wheels is represented by the third orange arrow. It seems to me that this display shows up during moderate acceleration after electric boost ends and before a stable "cruising" display appears.
This is not wasteful at all, IMHO. In fact, this is how to keep the ICE running at it's most efficient range.

When the load is low, eg. descending a slope or cruising, the surplus power from the ICE can be used by the Generator to provide electric power to the Motor to drive the car or/and to charge the battery at the same time.

When the load is high, eg. climbing a slope or passing, if the torque demand is greater than what ICE can provide, the battery joins in to assist.

In this way, the ICE can be operated at it's most efficient range and not be affected by load variations.

Vincent[/b]
 

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No activity to or from the battery-pack is an inherit requirement of the design. The PSD must rotate the generator to both keep internal pressure balanced and to be able to rapidly take advantage of discharging & recharging opportunities. So it does. And at times, you will see exactly that on the Multi-Display. Rather than a seemingly wasteful activity, it is actually gainful.

In fact, it is a strength that the mild hybrids envy. The upcoming Accord-Hybrid will offer the ability for low-demand A/C to run using only electricity. That sounds great... until you question where that electricity will actually come from. Unlike Prius having two motors, that system only has just one. That means it cannot supply electricity constantly like you see with Prius. When you observe a CVT Civic-Hybrid, you'll see that battery-pack (which has a much lower energy density than the HSD system) is managed rather well... avoiding forced recharging (which really hurts its MPG) by relying almost entirely on regenerative braking, yet still being able to take advantage of the charge-level available. That works well. But certainly doesn't leave much for the A/C to use.

Watch the Energy-Monitor screen. You'll be delighted with how responsive the flow of electricity is, rapidly changing for just a moment to seize a brief efficiency benefit. It's surprising smart and impressively responsive. But it couldn't be that way if that smaller motor wasn't used as a generator at the same time (while the engine is providing thrust to the wheels).

Cool, eh?

That original Toyota slogan of "Prius Genius" comes to mind.
 

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The display simplifies things a bit. The one motor in the picture is really two motor/generators. To avoid the need for an inefficient, complex automatic transmission that tends to wear out quickly and expensively, the engine spins one motor/generator to generate electricity for the other motor/generator to apply torque to the wheels. This is the primary means for getting torque to the wheels at low speed (up to about 60 MPH). The generator to motor electric path is about 90 - 95% efficient, slightly better than the best automatic transmission designs, but not quite as good as a manual transmission.

For a much more in-depth explanation, see Graham's site, mentioned above. It really is excellent.
 

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Discussion Starter #6
Thanks for all the replys :!:

I visited Graham's site, and a (simplified) explanation (that I can try to sell to my wife :lol: ) is that since the ICE always sends 72% of its torque to the wheels and 28% to the MG, if the MG does not need to charge the battery, it will send its output also to the wheels.

Did I get that right :?:

This is pretty complicated and tricky stuff :!:

No wonder Ford decided to pay Toyota for the technology for the Escape, instead of trying to figure it out themselves :!:
 

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Actually, it is a reduction of complexity compared to a traditional vehicle. Just take a look at an automatic transmission sometime.

Tweaking it, to squeeze out highest possible efficiency, does take some work though. Fortunately, Toyota is on year #8 already. So it's working pretty sweet at this point.

And Ford didn't actually use Toyota's technology. They "designed" their own. But to avoid a potential patent-infridgement lawsuit due to the similarity, they decided to strike a deal with Toyota by providing "good will" money.
 

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It's definitely a feature. The fact that it looks bizarre and complicated comes mostly from our knowledge of "conventional" transmissions, which are purely mechanical. Even if electronics controls the operation of a conventional automatic transmission, engine power is transmitted to the wheels in a purely mechanical way. This is in contrast to Prius transmission, which is of an "electro-mechanical" type, in other words, the power is transmitted partially mechanically and partially electrically. This is not a new idea : if you look at the USPTO website and search for patent number 3,732,751 (may 15, 1973) you will find a very detailed description of a Prius-like drivetrain... :shock:

Some people may be wrong when they're right too long before others ! :(
 
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