R
Roy
- Jan 1, 1970
- 0
From: bud
krw says...
John Gilmer wrote:
But with an electric car you can use the motor as a generator and do
regenerative braking converting most of the kinetic energy back to
electrical energy in the battery.
True. But the energy gained is, IMO, somewhat exagerated. In true
"stop & go" driving when you want to "stop" you want to STOP and you
don't want to screw around with "slowing down" with regenerative braking
first. Regeneration would work best on a long downhill stretch (without
STOPPING) after a long uphill stretch.
In my normal driving I don't make many fast stops. Prius has smaller
than normal brakes because of regenerative braking. And the city mpg
(stop and go)is better than highway. Regeneration must be quite
effective.
There is no benefit to a hybrid at highway speeds because the engine has
to run anyway. .,..and you're lugging the weight of the batteries along
for no benefit.
You can use a smaller engine, with battery/electric motor added for when
you need more power - acceleration, ascent. (For a very long fast ascent
where battery assistance is required you can run out of battery.) The
smaller engine operates at a more efficient point. The benefit - around
44 mpg highway for a Prius.
And with a conventional car you are lugging the weight of the higher
horsepower of the engine that is not being used most of the time.
In a Prius, at higher speeds the engine - through the transmission -
does not turn the wheels fast enough. One of the 2 electric motors is
used as a generator feeding the 2nd motor. That operates through a
planetary drive to increase the wheel speed. [See Hybrid Synergy Drive
in Wikipedia.]
The engine, by the way, is a variation that uses an Atkinson cycle
(which I had never heard of).
A hybrid has many of the same advantages although unless the power
management is somewhat predictive the cells might already be at 100%
charge when the regenerative braking is call upon.
I read Prius wants to keep battery charge between 40 and 60% of capacity
because it gives longer battery life (NiMH). I suspect on a long descent
they would run it up to 100%.
I would seem to be a *LONG* descent charge .4C or the batteries are too
small to be of much use.
Design of anything is a series of trade-offs.
----------
Roy responds: I agree., specially designing something as systemic as a
car., Therfor Quality Control is essential I believe this is where
product support came to play for product longevity.
Amazing what a beer or two does to refresh & calm me };-)
" Have a Great Weekend "
Roy Q.T. ~ US/NCU ~ E.E. Technician
[have tools, will travel]
krw says...
John Gilmer wrote:
But with an electric car you can use the motor as a generator and do
regenerative braking converting most of the kinetic energy back to
electrical energy in the battery.
True. But the energy gained is, IMO, somewhat exagerated. In true
"stop & go" driving when you want to "stop" you want to STOP and you
don't want to screw around with "slowing down" with regenerative braking
first. Regeneration would work best on a long downhill stretch (without
STOPPING) after a long uphill stretch.
In my normal driving I don't make many fast stops. Prius has smaller
than normal brakes because of regenerative braking. And the city mpg
(stop and go)is better than highway. Regeneration must be quite
effective.
There is no benefit to a hybrid at highway speeds because the engine has
to run anyway. .,..and you're lugging the weight of the batteries along
for no benefit.
You can use a smaller engine, with battery/electric motor added for when
you need more power - acceleration, ascent. (For a very long fast ascent
where battery assistance is required you can run out of battery.) The
smaller engine operates at a more efficient point. The benefit - around
44 mpg highway for a Prius.
And with a conventional car you are lugging the weight of the higher
horsepower of the engine that is not being used most of the time.
In a Prius, at higher speeds the engine - through the transmission -
does not turn the wheels fast enough. One of the 2 electric motors is
used as a generator feeding the 2nd motor. That operates through a
planetary drive to increase the wheel speed. [See Hybrid Synergy Drive
in Wikipedia.]
The engine, by the way, is a variation that uses an Atkinson cycle
(which I had never heard of).
A hybrid has many of the same advantages although unless the power
management is somewhat predictive the cells might already be at 100%
charge when the regenerative braking is call upon.
I read Prius wants to keep battery charge between 40 and 60% of capacity
because it gives longer battery life (NiMH). I suspect on a long descent
they would run it up to 100%.
I would seem to be a *LONG* descent charge .4C or the batteries are too
small to be of much use.
Design of anything is a series of trade-offs.
----------
Roy responds: I agree., specially designing something as systemic as a
car., Therfor Quality Control is essential I believe this is where
product support came to play for product longevity.
Amazing what a beer or two does to refresh & calm me };-)
" Have a Great Weekend "
Roy Q.T. ~ US/NCU ~ E.E. Technician
[have tools, will travel]
