Join Early Retirement Today
Reply
 
Thread Tools Display Modes
Question about a Prius (or an electric car)
Old 10-12-2011, 01:47 PM   #1
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
 
Join Date: May 2005
Posts: 17,203
Question about a Prius (or an electric car)

OK... today when driving to lunch I was sitting at a red light behind a Prius... now, my car is a manual and usually I just sit there without my foot on the brake.. but I noticed that the driver of the Prius had his foot on the brake... why?

IMO, and from the little I know, the engine does not even run while stopped.. so why would the car move at all if the person is not pushing on the 'go' pedal.... IOW, why would the car move at all if the driver does not want it to move... there should be no electricity going to the electric motor (that would seem to be a waste if it is)....

I have seen this before and have thought the same thing... why are they holding down the brake Does the car want to move if you do not hold down the brake If so, then why


Since I am on the subject of this car.... how is the AC unit Does the engine have to be on for it to work What about an all electric car? How much energy is expended on the AC unit.... and how does that affect your range of driving
Texas Proud is offline   Reply With Quote
Join the #1 Early Retirement and Financial Independence Forum Today - It's Totally Free!

Are you planning to be financially independent as early as possible so you can live life on your own terms? Discuss successful investing strategies, asset allocation models, tax strategies and other related topics in our online forum community. Our members range from young folks just starting their journey to financial independence, military retirees and even multimillionaires. No matter where you fit in you'll find that Early-Retirement.org is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with our members, see fewer ads, upload photographs, create a retirement blog, send private messages and so much, much more!

Old 10-12-2011, 02:01 PM   #2
gone traveling
 
Join Date: Apr 2009
Location: Eastern PA
Posts: 3,851
I had these same questions about the vehicle Fred Flintstone drove ...
rescueme is offline   Reply With Quote
Old 10-12-2011, 02:09 PM   #3
Thinks s/he gets paid by the post
MasterBlaster's Avatar
 
Join Date: Jun 2005
Posts: 4,391
Perhaps the Prius owner is worried that you could rear-end him and push him into traffic where he gets hit by a Hummer. Hence the foot on the brake.

Myself I wonder about and worry that the refrigerator light is still on whenever the door is closed.
MasterBlaster is offline   Reply With Quote
Old 10-12-2011, 02:45 PM   #4
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
Koolau's Avatar
 
Join Date: Jul 2008
Location: Leeward Oahu
Posts: 17,794
I'm with Master Blaster. Even though my mainland car was a manual, I typically took the car out of gear when stopping for a red light, but still kept my foot on the brake to lessen the chance of being pushed into an intersection by an errant driver from behind.

I too have wondered about the auxiliary equipment on a hybrid. How does the heater work if the engine hasn't warmed up? What runs the AC? What keeps the power brakes and steering active. Apparently, these are not significant issues as hybrids have taken over Oahu, but I'm still curious.

Since battery capacity is such a critical factor for hybrids (and all electrics) it would seem every effort would be made to minimize auxiliary electricity usage (e.g., probably use LEDs for every light source, maximum (legal) window tinting to limit AC usage, low-bypass recirculation of conditioned air, limited wattage of any standard sound system, etc. I once heard that standard headlamps (this was circa 1980) could cost 1 mpg.

I suppose I could Google for answers, but have wanted to ask a hybrid owner in person. I'm sure several on the forum own hybrids. My guess is many have become intimately familiar with the workings of their vehicles.
__________________
Ko'olau's Law -

Anything which can be used can be misused. Anything which can be misused will be.
Koolau is offline   Reply With Quote
Old 10-12-2011, 03:06 PM   #5
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
donheff's Avatar
 
Join Date: Feb 2006
Location: Washington, DC
Posts: 11,318
I don't have a Prius but I do have a hybrid (I won't say which for fear of being attacked as not sufficiently frugal). I hold my foot on the brake at red lights because I always have held my foot on the brake at red lights. I have no idea what would happen if I took it off -- if I remember to try it next time I drive the car drive I will report back. As for AC, I have sat waiting for DW for long periods and the A/C works. The internal combustion engine will come on periodically as needed.
__________________
Idleness is fatal only to the mediocre -- Albert Camus
donheff is offline   Reply With Quote
Old 10-12-2011, 03:30 PM   #6
Thinks s/he gets paid by the post
GregLee's Avatar
 
Join Date: Oct 2010
Location: Waimanalo, HI
Posts: 1,881
My wife always takes our manual shift car into neutral and rides the brake at stop lights. She says it hurts her foot to keep it extended pressing the clutch down, since her legs are short. And if you're not using your right foot for the clutch, it seems natural to use it for the brake, to keep the car from drifting. But this has nothing to do with electric cars, so it's probably not relevant.
__________________
Greg (retired in 2010 at age 68, state pension)
GregLee is offline   Reply With Quote
Old 10-12-2011, 03:41 PM   #7
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
Koolau's Avatar
 
Join Date: Jul 2008
Location: Leeward Oahu
Posts: 17,794
Quote:
Originally Posted by GregLee View Post
My wife always takes our manual shift car into neutral and rides the brake at stop lights. She says it hurts her foot to keep it extended pressing the clutch down, since her legs are short. And if you're not using your right foot for the clutch, it seems natural to use it for the brake, to keep the car from drifting. But this has nothing to do with electric cars, so it's probably not relevant.
Her technique limits throw-out bearing wear. Always did it this way and never replaced a throw-out bearing (or a clutch). But, YMMV.
__________________
Ko'olau's Law -

Anything which can be used can be misused. Anything which can be misused will be.
Koolau is offline   Reply With Quote
Old 10-12-2011, 03:45 PM   #8
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
travelover's Avatar
 
Join Date: Mar 2007
Posts: 14,328
My Escape hybrid will creep if you take your foot off the brake. It was designed that way to make it feel like a regular automatic transmission car.
travelover is offline   Reply With Quote
Old 10-12-2011, 03:52 PM   #9
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
 
Join Date: May 2005
Posts: 17,203
Quote:
Originally Posted by Koolau View Post
Her technique limits throw-out bearing wear. Always did it this way and never replaced a throw-out bearing (or a clutch). But, YMMV.
Our just put the car in neutral and not touch the clutch or the brake... as long as not on an incline you just sit...
Texas Proud is offline   Reply With Quote
Old 10-12-2011, 03:54 PM   #10
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
 
Join Date: May 2005
Posts: 17,203
Quote:
Originally Posted by travelover View Post
My Escape hybrid will creep if you take your foot off the brake. It was designed that way to make it feel like a regular automatic transmission car.

That seems strange as I would think that they have to have electricity going to the motor all the time to be able to creep... maybe it is so little it is a 'who cares' except for an electric only car...
Texas Proud is offline   Reply With Quote
Old 10-12-2011, 03:55 PM   #11
Thinks s/he gets paid by the post
BigMoneyJim's Avatar
 
Join Date: Feb 2003
Location: Nomadic in the Rockies
Posts: 2,720
The A/C compressor is electric. There is no "neutral" in the sense of a normal transmission. The wheels, electric motor/generator and gas motor I think are all mechanically linked to the planetary gear system, and the computer manipulates the planetary gear system depending on which force is going to drive another. (Regenerative braking, electric motor drives wheels, gas motor charges batteries by driving the electric motor, gas motor powers wheels.)

You stay on the brake or put the little joystick in "Park" to let the computer know you want to stay in place. The computer mimics the behavior of an automatic transmission. I'm not sure, but I think they put artificial gear-shift bumps in there and possibly affect how the car accelerates to make it "feel" like driving a normal car.

There are a bunch of batteries, and if they run low enough the engine will start to charge the batteries. This can happen whether the car is moving, sitting at a stoplight or in park. There is no "normal" starter in the car; the electric motor spins the gas motor on nearly instantly.

Edit: This post specifically refers to a Prius Hybrid Synergy drive system. Other hybrid drive systems may be completely different.
BigMoneyJim is offline   Reply With Quote
Old 10-12-2011, 04:09 PM   #12
Moderator
MBAustin's Avatar
 
Join Date: Jul 2010
Posts: 7,925
For those of you interested in Prius details - technical and otherwise - check out PriusChat. Also has info on hybrids in general.

I have a 2010 Prius IV and absolutely love it - never thought I would say that about a mode of transportation.
__________________
"One of the funny things about the stock market is that every time one person buys, another sells, and both think they are astute." William Feather
----------------------------------
ER'd Oct. 2010 at 53. Life is good.
MBAustin is offline   Reply With Quote
Old 10-12-2011, 04:15 PM   #13
Thinks s/he gets paid by the post
BigMoneyJim's Avatar
 
Join Date: Feb 2003
Location: Nomadic in the Rockies
Posts: 2,720
Here is an interactive model of the planetary gear system. EDIT: I mean the graphic if you scroll down on the page. Hover over the components and it will tell you what the gear is mechanically linked to.



This page has some photos of the system and a whole bunch of info I haven't even tried to skim.
BigMoneyJim is offline   Reply With Quote
Old 10-12-2011, 04:28 PM   #14
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
travelover's Avatar
 
Join Date: Mar 2007
Posts: 14,328
Quote:
Originally Posted by Texas Proud View Post
That seems strange as I would think that they have to have electricity going to the motor all the time to be able to creep... maybe it is so little it is a 'who cares' except for an electric only car...
It is sophisticated enough that it doesn't put electric power to the motor if the brake is on.
travelover is offline   Reply With Quote
Old 10-12-2011, 04:35 PM   #15
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
travelover's Avatar
 
Join Date: Mar 2007
Posts: 14,328
Quote:
Originally Posted by Texas Proud View Post
..........
Since I am on the subject of this car.... how is the AC unit Does the engine have to be on for it to work What about an all electric car? How much energy is expended on the AC unit.... and how does that affect your range of driving
On the original Escape hybrid, the engine had to be running to power the AC compressor. On the newer ones and the Fusion hybrid, there is an electric AC compressor. All-electric cars have electric AC compressors and resistance heaters. They take a big bite out of driving range.
travelover is offline   Reply With Quote
Old 10-12-2011, 08:16 PM   #16
Thinks s/he gets paid by the post
kyounge1956's Avatar
 
Join Date: Sep 2008
Posts: 2,171
Quote:
Originally Posted by donheff View Post
I don't have a Prius but I do have a hybrid (I won't say which for fear of being attacked as not sufficiently frugal). I hold my foot on the brake at red lights because I always have held my foot on the brake at red lights. I have no idea what would happen if I took it off -- if I remember to try it next time I drive the car drive I will report back. As for AC, I have sat waiting for DW for long periods and the A/C works. The internal combustion engine will come on periodically as needed.
I have a Prius, and I also keep my foot on the brake at red lights because that's what I've always done. You have to step on the brake to bring the moving car to a halt, and I doubt that I'd ever form a new habit of taking my foot off the brake once the car stopped, unless there was some specific reason to do so. Now that I'm thinking about it, I wonder—if you let up on the brake pedal of a hybrid once the car has come to a stop, do the brake lights stay lit or not? If I remember to try it next time I go for a drive, I too will report back.
kyounge1956 is offline   Reply With Quote
Old 10-12-2011, 08:58 PM   #17
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
 
Join Date: Jul 2006
Posts: 11,401
So the answer is psychology rather than physics. Interesting!
Meadbh is offline   Reply With Quote
Old 10-12-2011, 09:14 PM   #18
Full time employment: Posting here.
JakeBrake's Avatar
 
Join Date: Sep 2008
Location: Southeast USA
Posts: 548
I don't know anything about hybrids, but I do know that if you're old and absent-minded like me, it's possible for your vehicle to creep foward or backward when it's supposed to be stopped and you not be aware of it. So, IMHO, it's a good idea to have the habit of keeping your foot on the brake when stopped until you shift into park on an automatic or apply the hand brake on a manual.
JakeBrake is offline   Reply With Quote
Old 10-12-2011, 10:01 PM   #19
Moderator Emeritus
Nords's Avatar
 
Join Date: Dec 2002
Location: Oahu
Posts: 26,856
Quote:
Originally Posted by Texas Proud View Post
OK... today when driving to lunch I was sitting at a red light behind a Prius... now, my car is a manual and usually I just sit there without my foot on the brake.. but I noticed that the driver of the Prius had his foot on the brake... why?
IMO, and from the little I know, the engine does not even run while stopped.. so why would the car move at all if the person is not pushing on the 'go' pedal.... IOW, why would the car move at all if the driver does not want it to move... there should be no electricity going to the electric motor (that would seem to be a waste if it is)....
I have seen this before and have thought the same thing... why are they holding down the brake Does the car want to move if you do not hold down the brake If so, then why
The Prius will crawl at 1-2 MPH when your foot's off the gas (and off the brake) just like an automatic-transmission car. I don't know why the Prius does that.

If you want to stop that then you can put the car in neutral or in park, but to go back to drive you have to remember to put your foot on the brake while you're moving the paddle shifter. So most people leave it in drive and leave their foot on the brake.

The car's computer will keep running all the auxiliaries, and it'll start the engine as necessary to recharge the main battery. That's all separate from propulsion.

Quote:
Originally Posted by Texas Proud View Post
Since I am on the subject of this car.... how is the AC unit Does the engine have to be on for it to work What about an all electric car? How much energy is expended on the AC unit.... and how does that affect your range of driving
Quote:
Originally Posted by Koolau View Post
I too have wondered about the auxiliary equipment on a hybrid. How does the heater work if the engine hasn't warmed up? What runs the AC? What keeps the power brakes and steering active. Apparently, these are not significant issues as hybrids have taken over Oahu, but I'm still curious.
They're all powered through a DC-AC inverter. The heater has resistive strips (ours are probably thickly coated with dust) and the A/C makes the inverter work hard to keep cold air flowing. As the inverter discharges the main battery, the Prius' computer(s) turn on the internal combustion engine to recharge the battery.

Same deal with the rest of the car's aux equipment. That inverter is almost as critical to the car's operation as the main battery is to its propulsion, but they're both pretty reliable.

I have some old habits that are no longer relevant but are still emotional triggers. For example when the Prius is turned on, after a few seconds the internal-combustion engine fires up for about 45 seconds and charges the battery. It has nothing to do with anything in the battery or the ICE-- it's just to warm up the catalytic converter (with ICE exhaust) so that the car qualifies for its EPA rating as a "practically zero emissions vehicle".

I know this. But when my daughter turns on the car and then starts fiddling with her iPod while the ICE burns gas, it drives me nuts. I can still hear my mother from 1976 screeching "Stop wasting gas!!" Yet no gas is being "wasted" other than as designed.
__________________
*

Co-author (with my daughter) of “Raising Your Money-Savvy Family For Next Generation Financial Independence.”
Author of the book written on E-R.org: "The Military Guide to Financial Independence and Retirement."

I don't spend much time here— please send a PM.
Nords is offline   Reply With Quote
Old 10-13-2011, 06:51 AM   #20
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
RunningBum's Avatar
 
Join Date: Jun 2007
Posts: 13,202
I'd guess that the Prius rolls a bit with the brake off to make for a more gentle acceleration. You take your foot off, the car edges forward, so when you hit the gas pedal (do they call it that?), it's a smoother transition from 2 mph than from 0 mph.

I agree with the safety reasons for keeping your foot on the brake too. It's what I do in my manual at a stop. I put it in neutral, so it would not roll unless I'm on a hill. But I don't want to get bumped into an intersection, and I want the brake lights on so that a car coming up from behind me knows that I'm stopped. Finally, it's not always obvious if I'm on enough of a hill that I'd roll ahead or back, so if I always use the brake I'm not going to misjudge ground that looks flat.
RunningBum is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
So which car should I let my kid drive? hakuna matata Other topics 48 08-31-2011 06:35 PM
BBB Arbitration Agreement for new car purchase? ERD50 FIRE and Money 7 07-27-2011 03:34 PM
Should I buy a second car? mickeyd Other topics 40 07-12-2011 08:10 PM
Buying a car for the first time and need one quickly plex Other topics 14 06-30-2011 07:16 PM
Help for DD#2 - neighbor and damaged car MichaelB Other topics 32 06-26-2011 07:20 AM

» Quick Links

 
All times are GMT -6. The time now is 08:02 PM.
 
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.