Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 07-20-2012, 10:57 AM   #31
Member
 
Join Date: Apr 2012
Location: NY
Posts: 92
Rewards Points: 75
Default

Pre-wiring Electric Vehicle charger


If we take the Tesla Roadster as an example and use the information in Wikipedia (http://en.wikipedia.org/wiki/Tesla_Roadster#Recharging):

@ 15A 120V, it takes 48 hours for a full recharge
@ 90A 240V, it takes 4 hours for a full recharge

By my calculations:
@ 2880A 240V (or 90A 7.7kV), it will take 8 minutes for a full recharge.

WOW! I don't see that happening at home.

sixspeed is offline   Reply With Quote
Old 07-20-2012, 08:07 PM   #32
Licensed Electrical Cont.
 
Speedy Petey's Avatar
 
Join Date: Feb 2004
Location: NY State
Posts: 6,864
Rewards Points: 2,032
Default

Pre-wiring Electric Vehicle charger


Quote:
Originally Posted by sixspeed View Post
WOW! I don't see that happening at home.
It sure would be fun to try though.
__________________
Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.
Answers based on the 2008 & 2011 NEC.
Speedy Petey is offline   Reply With Quote
Old 07-20-2012, 09:01 PM   #33
Member
 
Join Date: Jan 2012
Posts: 210
Rewards Points: 150
Default

Pre-wiring Electric Vehicle charger


Let me throw some more interesting information into the debate...An ICE engine is only about 25% efficient for gasoline, and 35% efficient for a diesel. Why is it so low? Well, ICE engines throw away just about all the heat energy made by the combustion of the fuel, and only use the mechanical expansion of the gases when they explode for energy.

Fossil fuel Power plants however can approach 50% efficiency ratios. This is because they use the heat energy, IE steam. The typical fossil-fuel (and nuclear) plants use the heat energy produced to superheat steam, and that's what turns the generators. Some modern natural gas turbine plants actually approach 65% efficiency. These are called "Dual conversion" They first burn the natural gas in a ICE turbine engine which gives about 25% efficiency. The hot exhaust gasses are then used to boil steam and turn a second turbine, thus recovering another 40% or so of the heat energy in the fuel.

So, why cant this technology be used in an automobile? Well, it would simply be too bulky. Power plants do not need to move, like an automobile does, nor do they need to operate at different speeds and load conditions, different temperatures, etc. The next best thing is an electric vehicle. Yes, there are transmission losses, and an electric vehicle is not 100% efficient either...they are more like 90% efficient. So, it is really a wash, because electric vehicles from beginning to end are about the same...25% efificient once everything is all added up.

Here's some other facts to think about too. In normal driving ranges, most gasoline engines are only producing about 1/4 their rated power. This is the reason why such powerful engines are needed in typical automobiles when compared to the HP ratings of electric vehicles. The maximum power produced by an automobile engine is produced at very small RPM range at the top of their maximum speed range. You may not need 200 horsepower to move your sedan down the highway, but you do need 50 horsepower, and that's all that's available at 2000 RPM All 200HP does not come into play unless you rev the engine up to 5000 RPM. Electric engines however operate in the exact opposite range. The maximum torque an electric motor can produce is available at ZERO RPM. Torque in an electric motor falls off as the motor speeds up. Electric vehicles have EXCELLENT acceleration because of this, but their maximum speed is limited, because the motor runs out of torque at high speeds. This however is where a gasoline motor kicks in, and this is why hybrid automobiles are so efficient NOT really because they recover power in stop and to driving, but because they have two propulsion sources that operate with completely opposite efficiency and power curves!

Last edited by av-geek; 07-20-2012 at 09:09 PM.
av-geek is offline   Reply With Quote
Old 07-21-2012, 06:05 AM   #34
Licensed Electrical Cont.
 
Speedy Petey's Avatar
 
Join Date: Feb 2004
Location: NY State
Posts: 6,864
Rewards Points: 2,032
Default

Pre-wiring Electric Vehicle charger


Quote:
Originally Posted by av-geek View Post
..........., and this is why hybrid automobiles are so efficient ...........
If hybrids are SO efficient, then I REALLY need you to explain to me why the average Prius only gets 45-55 MPG, when most small diesels get the same if not more.
__________________
Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.
Answers based on the 2008 & 2011 NEC.
Speedy Petey is offline   Reply With Quote
Old 07-21-2012, 08:06 AM   #35
Member
 
Join Date: Jan 2012
Posts: 210
Rewards Points: 150
Default

Pre-wiring Electric Vehicle charger


The extra 10 percent of efficiency that a diesel engine has over a gasoline engine is nothing to sneeze at, and that is where your extra fuel mileage comes from. Diesel engines are more efficient because they have a higher compression ratio. There are other advantages that the diesel offers too, for instance, the fuel produces more BTU's per gallon than gasoline. Also, diesel engines have a much wider power range (even though their maximum RPM is lower) and are both more useful and efficient over a wider RPM range than a gasoline engine.

All of these factors make diesel engines much more efficient than a gasoline engine especially on the open road where I imagine you are getting most of your driving, and good mileage figures (and also the reason why long haul big trucks use them too!) A hybrid however shines in around-town travel, where most people do their traveling...You know, those trips to the grocery store or other shopping where you are scheping down the main thorofare in town with all those out of phase traffic signals starting and stopping. In big cities too, where the highways stay clogged with heavy traffic, the hybrid shines too, and where another advantage of them shows up...the engine can shut completely off when stopped. Over here on the east coast, many people are getting some amazing numbers out of their Priuses getting to work and back!

On the open road, a hybrid is really like no other gasoline vehicle. The mileage of a Prius of 40-45MPG is really nothing to laugh about though...it is a mid-size car capable of carrying 5 grown adults in comfort (I rode to florida with the in-laws family in one) That is something most mid-size gasoline powered vehicles cannot come close to, but most of this good highway mileage is attributed to good design, like aerodynamics and such. The Prius really shines around town in stop-n-go stuff, where it's mileage can get well above 50 MPG's. There are also different degrees of Hybrids too. The hybrids by Honda are very mild and use an ordinary transmission (the Prius uses a CVT) GM also builds hybrids for their pickup trucks too, but they only are capable of stopping the engine when the vehicle stops and the electric side does not power the vehicle while moving.

What I would really like to see though is a hybrid diesel! I'm not sure why the auto makers are shunning this, but it's probably way too efficient!
av-geek is offline   Reply With Quote
Old 07-21-2012, 09:39 AM   #36
Member
 
Join Date: Dec 2011
Location: Livermore, California
Posts: 265
Rewards Points: 250
Default

Pre-wiring Electric Vehicle charger


Speedy Peety,
I've never really paid attention to the small diesels. Could you point me at some of the models that are getting in the 50 MPG range? Looking at the US 2012 car lineup (http://cargasmileagecomparisons.net/...y-comparisons/), I'm seeing 31 (city) / 43 (highway) as the best diesel, 36/37 and 30/40 competing for the best gas, and 53/46 for a hybrid. Now the non-hybrid numbers feel a bit low to me, so I'm wondering if there's a better source.

As a side note, if the models you've been seeing with better gas mileage are European, remember that they have laxer safety standards. Which in turn allow their cars to be lighter and get better gas mileage.

av-geek,
Remember that diesels are heavier. And once you add up all the direct & indirect weight additions (such as crumple zones), an initial diesel hybrid may actually be less efficient than a gasoline one. Looking at the numbers on the sight above, I was actually quite surprised that diesel didn't have more of an advantage.

Also you do have to account for human irrationality when it comes to choosing vehicles. How many folks do you know willing to drive a mile or two to get gas that's a few cents cheaper per gallon, and thus blow all their savings in the cost of fuel to get to the station? Until we find a way around that mentality, many folks with see the higher price of diesel and rule out the possibility of a diesel car without even looking enough to see the higher MPG.
a_lost_shadow is offline   Reply With Quote
Old 07-21-2012, 10:24 AM   #37
Licensed Electrical Cont.
 
Speedy Petey's Avatar
 
Join Date: Feb 2004
Location: NY State
Posts: 6,864
Rewards Points: 2,032
Default

Pre-wiring Electric Vehicle charger


Quote:
Originally Posted by a_lost_shadow View Post
Speedy Peety,
I've never really paid attention to the small diesels. Could you point me at some of the models that are getting in the 50 MPG range? Looking at the US 2012 car lineup (http://cargasmileagecomparisons.net/...y-comparisons/), I'm seeing 31 (city) / 43 (highway) as the best diesel, 36/37 and 30/40 competing for the best gas, and 53/46 for a hybrid. Now the non-hybrid numbers feel a bit low to me, so I'm wondering if there's a better source.
I don't go by published numbers. IMO none of them are accurate. Hell, even the in-car computer in Priuses are known to be skewed in favor of higher numbers than actual. Something about taking into account wind resistance or some other BS.

I ask actual folks what their actual numbers are. Even many car shows do MUCH better real-world tests than the numbers on window stickers tell.

I know a man with a 90-something Jetta diesel, with almost 300k on the clock. Now keeping in mind he is an older really calm gentleman, he gets 50-60mpg.....on average.
Like I said earlier, Top Gear UK did a real world test on a VW Lupo (tiny little thing) and got 80mpg highway only.

There are a TON of Priuses around here. Most folks I have talked to are getting under 50mpg daily. Some even reported 35-40 around town.
__________________
Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.
Answers based on the 2008 & 2011 NEC.
Speedy Petey is offline   Reply With Quote
Old 07-21-2012, 04:21 PM   #38
Member
 
Join Date: Dec 2011
Location: Livermore, California
Posts: 265
Rewards Points: 250
Default

Pre-wiring Electric Vehicle charger


Most of my friends have cars older than 5+ years, thus I really only have published numbers to fall back on if I want to include the efficiency gains of the last few years. For my driving habits with non-hybrid cars in the US, I've found them to be pretty accurate (+/- 2 MPG). For hybrid cars, I take them with a grain of salt. I know a few years ago the car companies were fighting with the EPA to allow them to advertise hybrid mileages lower than the EPA estimates. At the time the EPA test was skewed so it artificially inflated the hybrid mileages. Thus the car companies wanted to report something closer to what consumers could expect. Still the few Prius owners that I've talked to say they get around the advertised mileage if they don't drive aggressively. If they do drive aggressively, then the mileage plummets. Also, I believe that on all but the latest model of Prius having the AC on kept the engine on and thus also caused a big hit to mileage.

Thank you for the information on the Lupo. It's interesting to see what VW did to improve gas mileage (no power steering, no ac, reduced emissions filtering, etc.).
a_lost_shadow is offline   Reply With Quote
Old 07-21-2012, 11:37 PM   #39
Member
 
Join Date: Jul 2012
Posts: 119
Rewards Points: 75
Default

Pre-wiring Electric Vehicle charger


Quote:
Originally Posted by Speedy Petey View Post
I don't go by published numbers. IMO none of them are accurate. Hell, even the in-car computer in Priuses are known to be skewed in favor of higher numbers than actual. Something about taking into account wind resistance or some other BS.

I ask actual folks what their actual numbers are. Even many car shows do MUCH better real-world tests than the numbers on window stickers tell.

I know a man with a 90-something Jetta diesel, with almost 300k on the clock. Now keeping in mind he is an older really calm gentleman, he gets 50-60mpg.....on average.
Like I said earlier, Top Gear UK did a real world test on a VW Lupo (tiny little thing) and got 80mpg highway only.

There are a TON of Priuses around here. Most folks I have talked to are getting under 50mpg daily. Some even reported 35-40 around town.
You're writing your own reviews - but worse, when you read them...you believe them. As you said, "IMO". You have no facts to back most of what you say here... It's all just...hot air.
kontoose is offline   Reply With Quote
Old 07-21-2012, 11:46 PM   #40
Member
 
Join Date: Jul 2012
Posts: 119
Rewards Points: 75
Default

Pre-wiring Electric Vehicle charger


My grandmother had a steam car. It never went anywhere...but her skin was without blemish.

kontoose is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
Electric cooktop wiring issues kbrookst Electrical 17 04-13-2012 01:36 PM
Wiring Electric Range Ringo2 Electrical 6 05-23-2011 05:49 PM
90 amp electric car charger! The future... Billy_Bob Electrical 16 02-16-2010 02:01 PM
Wiring from electric motor subman Electrical 1 06-24-2005 10:37 PM
Wiring from electric motor Submarineman Electrical 1 06-17-2005 12:50 AM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.