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Question on hybrid cars
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#11
 
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Re: Question on hybrid cars -
12-09-2005
, 08:46 PM
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Andrew Stephenson wrote: The Prius does a good job of emulating a conventional automatic gearshift car. On the dashboard is a button which has the same effect as shifting the lever to Park. It locks the transaxle as usual and is strong enough for level ground. The knob to select [R]everse/[N]eutral/[D]rive (and new [b]attery-recharge option) is just below this button, with functions lined up in the same sequence as on a standard gear lever: imagine the arc which your hand moves through during operation of a standard shift; the same arc is followed in a Prius, just higher up at dashboard level. The B position is an engine braking function. Seems to me its only purpose is to help in long downhill runs, simulating a stick shift car using the engine to back down a little. |
to the car to charge the battery using regenerative braking. The
driver will be in a better position to know the road ahead so can
tell the car to recharge (and, incidentally, slow down). Most of
the time, I find this function of little use; but it's nice to be
able to choose. As it happens, I do employ it most to apply some
e-braking where foot-braking is not essential; but that certainly
is not its primary function. Start relying on it and one day you
may find the battery can't take more charge -- then braking won't
be as hard as hoped and you suddenly have to f-brake anyhow. <g>
At least, all of the above is based on recollections of a tedious
trawl through the handbook, as well as general Toyota propaganda.
--
Andrew Stephenson
#12
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Not to be picky, actually it is touted as an optional instruction to the car to charge the battery using regenerative braking. The driver will be in a better position to know the road ahead so can tell the car to recharge (and, incidentally, slow down). Most of the time, I find this function of little use; but it's nice to be able to choose. As it happens, I do employ it most to apply some e-braking where foot-braking is not essential; but that certainly is not its primary function. Start relying on it and one day you may find the battery can't take more charge -- then braking won't be as hard as hoped and you suddenly have to f-brake anyhow. <g |
whenever you back off the accelerator. The book also mentions that the B
function shouldn't be used as a practice, because it will get poorer gas
mileage. I see the only purpose as engine braking, but then I am a new
owner (a week or so).
Gary Eickmeier
#13
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The Prius subsystem which handles braking is a blend of electric regenerative and conventional hydraulic technology. As you tread on the brake pedal the system notes how you did so: how hard; and how suddenly. From this, it works out (very fast) what braking force is required. As much of this as possible is provided by regenerative braking; the rest of done by hydraulic braking (with the usual brake pads and such). There are several useful benefits from this. (a) If either of the available braking methods fails, the other continues to provide some kind of slowing force. If the electric side fails, I infer the hydraulic provides all of what's needed. |
references of your own or Toyota's. As I said above, I think there will
be engine braking only when you are using the B function of the shift lever.
Gary Eickmeier
#14
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Andrew Stephenson wrote: Not to be picky, actually it is touted as an optional instruction to the car to charge the battery using regenerative braking. The driver will be in a better position to know the road ahead so can tell the car to recharge (and, incidentally, slow down). Most of the time, I find this function of little use; but it's nice to be able to choose. As it happens, I do employ it most to apply some e-braking where foot-braking is not essential; but that certainly is not its primary function. Start relying on it and one day you may find the battery can't take more charge -- then braking won't be as hard as hoped and you suddenly have to f-brake anyhow. <g That can't be right. |
Quote:
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We all know that the Prius regenerates power whenever you back off the accelerator. |
very (NB) light touch on the brake, as well as by a similar touch
on the accelerator. Mostly the car decides for itself whether or
not to insist on charging the battery, or not doing so. Keep in
mind, you are not the boss where such matters are involved. Have
you noticed how many gauges are not provided in a Prius? (Such
as engine rpm and temperature.)
Quote:
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The book also mentions that the B function shouldn't be used as a practice, because it will get poorer gas mileage. |
then recovering the charge to drive the electric motor is smaller
than the efficiency of driving the wheels more directly: either
by the petrol (US:gas) engine alone or by the petrol engine via
the generator driving the electric motor -- which happens more
often than some people imagine.
I have a theory, yet to be tested, that one could actually obtain
better mileage by the judicious application of a bit of welly: by
forcing the car to drive directly from the petrol engine and/or
"engine-->generator-->motor", one could cut from the loop the
comparatively lossy battery. But that _is_ still just a theory.
Quote:
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I see the only purpose as engine braking, but then I am a new owner (a week or so). |
end, use it in whichever way works for you. Later versions of
the technology will, I expect, enforce whichever practices have
been found to be best.
Tip, FWIW: the rear lower storage area (ie, beneath the fold-up
panels, where the spare tyre lives) can be made more useful by
placing the (separate purchase) optional Toyota rubber mat over
the spare. You can fold up the rearmost section of the panelling
and sit small/medium coolboxs (up to tall enough for 2-litre soft
drinks bottles) securely in the "slot".
--
Andrew Stephenson
#15
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Andrew Stephenson wrote: [explanation of the Prius subsystem which handles braking and how it affects the [b] function] I question this explanation, and hope you can back it up with further references of your own or Toyota's. As I said above, I think there will be engine braking only when you are using the B function of the shift lever. |
have seen I mentioned asking Toyota UK for technical data. They
provided lavish documentation with diagrams, which prompted my
synopsis and inferential explanation. If you have another, I'd
be interested to hear it. If your objections are simply that you
prefer not to believe (or you are trolling), I can't help you.
--
Andrew Stephenson
#16
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Andrew Stephenson wrote: Not to be picky, actually it is touted as an optional instruction to the car to charge the battery using regenerative braking. The driver will be in a better position to know the road ahead so can tell the car to recharge (and, incidentally, slow down). Most of the time, I find this function of little use; but it's nice to be able to choose. As it happens, I do employ it most to apply some e-braking where foot-braking is not essential; but that certainly is not its primary function. Start relying on it and one day you may find the battery can't take more charge -- then braking won't be as hard as hoped and you suddenly have to f-brake anyhow. <g That can't be right. We all know that the Prius regenerates power whenever you back off the accelerator. The book also mentions that the B function shouldn't be used as a practice, because it will get poorer gas mileage. I see the only purpose as engine braking, but then I am a new owner (a week or so). |
In hilly terrain I use the B setting in lieu of braking on steep
downslopes. Else, I leave it alone. The problem with using B for
slowing in traffic is that it doesn't trigger the brake lights.
The hypnotic energy-transfer animation shows that even on level ground
the gas engine periodically charges the main battery. The book's advice
against using B applies to travel on level ground where indeed the
practice does reduce the gas mileage.
Brent
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