Prius seldom runs on batteries alone?

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wrote:


That's another thing. The minimum speed thing on CC. Why not let it start at 10 MPH or so? I use it a lot when the speed limit is, say, 40MPH. It prevents me from accidentally going faster, which I can so easily do. But I cannot use it for a speed limit of 30, which we have around here on windy rural back roads. I would really like to set it at 33 and just let it go, but alas I cannot. I perceive this as another flaw. (The Jeep is the same way, engages at about 35). Tomes
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<snipped>

IIRC, the minimum speed to set cruise control on a Toyota is around 25 MPH, below which, the CC will not set and the memory clears. I can set the CC on our 3 Toyotas at 30 MPH, which I do in areas where the police often sit ;-)
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     rokigawaATtristarassociatesDOTcom "Ray O" writes:

Have to break the habit of a lifetime and agree with Ray. <g> My Prius definitely allows me to set 30mph. Haven't tried any lower (except maybe 29mph).
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Andrew Stephenson


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On Feb 18, 10:56 pm, "Ray O" <rokigawaATtristarassociatesDOTcom> wrote:

US 2004 Owner's Manual, section 2-6 "Operation of Instruments and Controls, "POWER switch, transmission, and parking brake," "Cruise Control," page 141: "The cruise control allows you to cruise the vehicle at a desired speed over 40 km/h (25 mph) even with your foot off the accelerator pedal."
Myself, I've been able to set the cruise control at 24mph, so I'd guess that the kph is the more important trigger there...
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"Ray O" <rokigawaATtristarassociatesDOTcom> wrote in message

Yeah, I just looked it up and it is supposed to be 24 MPH on the Prius. That's better than I thought. But still, I would like to see a minimum of 'already engaged in forward motion' rather than any minimum. Tomes
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<snipped>

The minimum speed for cruise control has been 25 MPH since cruise control first appeared on Toyotas. My guess is that speed was chosen to prevent someone trying to use it in stop-and-go driving.
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Interesting advice -- I'll have to try this.

The B transmission setting is my favored way of doing this. I believe it saves the brake pads, and it does not bother my passengers.
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I recommend just using the brakes - they don't normally use friction above 12 mph or so. The brakes on my 106K mile Prius are nearly at original thickness.
"B" mode is somewhat less efficient than using the brakes, because it reduces regeneration. That doesn't make a huge difference, but just braking is easier, too. "B" mode is useful on long downhills, especially if the drop is more than 2000 ft. When the battery is fully charged the friction brakes start getting wear.
Mike
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OK, I know I have read this, and what I have read has not always been the same thing. In your words, what exactly does 'B' mode do and how? Thanks. Tomes
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<snipped>>

According to the faq section at www.toyota.com: "B" is the position for engine braking. Engine braking assists the brakes in slowing the vehicle. It serves a similar function to downshifting on an automatic transmission. This position is intended for going down long declines, and utilizes the electric motor to slow the vehicle and regenerate electricity. For more information please reference Section 2 of your Owner's Manual.
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"Ray O" wrote ...

OK, that's what I thought. It uses the electric motor in reverse to generate electricity stored in the batteries. The IC engine remains out of the picture. Now my next question is does it generate more or less than in normal mode? Tomes
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I think that's backward - it dumps energy into turning the engine rather than into the battery. Maybe MRV can explain it more clearly. She does that sort of thing so well :-) People who have monitored the battery current with the Ecrostech Miniscanner (http://tinyurl.com/2yvbrx ) report less regeneration in "B." I've never actually checked myself, but if you want numbers I can do that.
Mike
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Thanks, interesting reading there. So now I am re-understanding this as follows: In B mode it spins the IC engine without starting the engine, wasting off excess energy in that spinning. What is not explained to me yet (his section of How B Mode Works was truncated off) is does it generate electricity in this engine spinning (the reverse of how it starts the engine up all the time)?
I think that I gleaned from this stuff that it makes less electricity in B mode due to the spinning waste. Tomes
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OK I found this other link that actually explains it pretty well, if anyone cares :-). http://www.techno-fandom.org/~hobbit/cars/b-mode.html Here is a bit copied out of that: .....Enter "B" mode. As in, "trucks use lower gear". By forcing the wheels to spin the engine and pump air, a good deal of that energy can be turned to heating the air going through the engine instead of heating the brake parts. Since fresh air is always coming into the engine, having it leave as much warmer air provides a convenient place to dump excess energy. In a conventional car the wheels push the engine around through the transmission, but the Prius needs to help that process out a little bit by actually having its combination of electric motors spin the engine. In this case, the valve-timing in the Prius engine is advanced to increase the amount of air taken in and the suction against the throttle flap -- which uses much more energy than the coasting-in-"D" scenario above......
There is a lot more there that I have not copied here, but in addition to capturing some of the energy, it is spinning it off in B mode.
Bottom line is to not use it in the hopes of saving more energy. Tomes
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On Sun, 18 Feb 2007 18:42:01 -0700, "Michael Pardee"

More critically, the brakes will overheat and fail if used to control speed on a long/steep descent.
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wrote:

Possibly. The brakes are not especially big, and here in the States the rear brakes are drum type. I understand in Europe they are 4-wheel disks. Anyway, use "B" for long descents.
Mike
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Are you sure about this 12 mph or so? It sounds like I'm hearing pad friction at higher speeds.

How do you know it reduces regeneration using B instead of braking? Do you mean braking is more radical (more force) yielding more regenerated power? Guess I'm used to manual transmission and want something to do. But I see the battery charging quickly when the Prius is in B.

I wonder if the US Touring model also has 4-wheel disk brakes?
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wrote:

Bill - read this link regarding what it does in B Mode: http://www.techno-fandom.org/~hobbit/cars/b-mode.html It answered a bunch of questions for me about 5 minutes ago. Basically, B mode wastes off excess energy by spinning the IC engine. Read on.... Tomes
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Thanks Tomes! That was illuminating and contained many surprises, e.g. "When accelerating... D and B produce the same behavior."
Do you know about "the Great Database Fire" that took out Priuschat? A similar thing happened to one of the chat sites I visit, BoaterTalk. That's one big downside of chat websites versus group (Usenet) news. OTOH I suppose Google could discontinue groups so we wouldn't be able to search back posts any longer.
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wrote:

You are welcome, glad to be able to actually contribute something other than opinion. It is a pretty good read, I just hope it is all correct :-).
What is this Priuschat? Or is the question what _was_ Priuschat? Tomes
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