Electric & Alt Fuel Vehicles, Part 3

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Darell

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Welcome to EV and AF part THREE! The

This is a continuation of Part 2 of the same thread. Diesel Dave will be thrilled to see that we now earned a Part 3. /ubbthreads/images/graemlins/smile.gif

So, my welder arrived today, but no tank of inert gas, and no plasma cutter yet. Can't weld until I can first cut that little Kewet all up!
 

Brock

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[ QUOTE ]
I'll lock this one before we surpass the 200-post threshold, and start a new one.

[/ QUOTE ]

ummm, Darell a little premature don't ya think? We were only at 148 /ubbthreads/images/graemlins/hahaha.gif Sorry I just couldn't resist.

Back on topic, the bad part I see about the Kewet is it does look like a glorified golf cart. Not that it is a bad thing, but you know that is what people think of when you say an electric car.

Having said that it would be perfect for me to go to and from work, 45mph max, 20 miles each way.
 

Darell

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[ QUOTE ]
Brock said:
[ QUOTE ]
I'll lock this one before we surpass the 200-post threshold, and start a new one.

[/ QUOTE ]

ummm, Darell a little premature don't ya think? We were only at 148 /ubbthreads/images/graemlins/hahaha.gif Sorry I just couldn't resist.

[/ QUOTE ]
Yeah... I figured if we could go a full day without a post, it was a good chance to make the break before I forgot.

[ QUOTE ]
Back on topic, the bad part I see about the Kewet is it does look like a glorified golf cart. Not that it is a bad thing, but you know that is what people think of when you say an electric car.

[/ QUOTE ]
I totally agree. Way above a GEM in all ways, but I fully relize the problem here!
 

Saaby

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Sweet on the Kewet! Maybe if you strip all the "Electric Vehicle" decals off of it and stick a fog generator in the thing you can make people think it's a poor running ICE /ubbthreads/images/graemlins/grinser2.gif
 

Darell

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If we can get this thing to burn rubber, as I think we will, then we should silence at least some of the laughter. /ubbthreads/images/graemlins/smile.gif
 

Darell

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.... but we'll never power BIG vehicles with batteries...

How often do I hear that? Most of us know about the serial hybrid switching locomotives that work better than the full diesel jobbies... but what about closer to home? A 72 passenger schoolbus! With 100+ mile range and fast charging...

Napa Valley Unified School District Case Study

>
> The Ovonic NiMH battery systems have a proven track record,
> delivering record-breaking range in a number of vehicles. Our
> battery systems hold the world record at 373 miles on a single
> charge set during the Tour de Sol competition in 1997. Our battery
> systems are beginning to be used in heavy-duty transit vehicles. An
> example is the all-electric 72-passenger school bus that carries
> students to and from school at the Napa Valley Unified School
> District in California. The 30,000+ pound prototype school bus is
> powered by a robust, energy-dense NiMH battery system with >100 kilo-
> watt hours (kWh) of energy storage that provides >100 mile range.
> Our NiMH battery systems provide about 25% greater range, 50%
> reduction in weight, and improved safety, life, and reliability over
> the lead-acid version. At mid-day, the Blue Bird electric bus is
> capable of rapid-charging via a 60 kilo-watt (kW) fast-charger
> provided by AeroVironment, who collaborated with our team on the
> advanced battery management system. Our NiMH battery systems that
> powered the school bus was developed through partial funding from
> the Defense Advanced Research Project Agency (DARPA), the California
> Energy Commission (CEC), and the Sacramento Municipal Utility
> District (SMUD).

http://www.cobasys.com/solutions/featured_solutions.htm
 

Orion

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Okay, . . .am I all wet on my thinking here?

Earlier [in part 2 /ubbthreads/images/graemlins/wink.gif], someone mentioned having a backup battery in the car of a BEV. Isn't there a way to have a backup battery that you can switch back and forth between [the primary and secondary] and while one battery is being used, regenerative braking and whatever else could be charging the other battery, and the driver would switch back and forth between the two. And as the one battery reaches depleation, the other battery would be charged up, the driver switches to that battery, and the depleated one then gets charged. Wouldn't that work? Seems to me it should. Regenerative braking charges the battery in a Hybrid car, why can't it charge two batteries as I laid out above?

By the way, the next car we get will probably be the Prius because it is about the most 'green' car I can get in my city.
 

Brock

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Splitting the battery bank in to two mean each one can only be charged at half the rate. So say when you break you put out 100amps. Now the main normal pack can only absorb 50 amps. So you are already throwing out 50 amps of heat to the conventional brakes because the battery pack can't take all the breaking power back in. Now if you are using two packs at 25 amps each you can only absorb 25 amps on which ever pack your using and loose 75 amps. Even if you had 2 of the larger packs you can still only grab 50 amps. So the best thing to do is double the size of the main pack and be able to put all 100 amps in at once loosing less to actual break heating. But as Darell pointed out, the larger the pack the more weight and the more power generated during braking and the more power needed to get the thing moving again. So at some point you have to stop adding batteries to catch all the power and choose a happy medium

these numbers are just used as an example, I have no idea how many amps are really pushed back in to the battery bank during breaking on the Rav 4 or any of the HEV's
 

Darell

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I think Brock answered it right. /ubbthreads/images/graemlins/smile.gif

Short answer: There is no reason to have two packs - any regenerative braking puts power back into the main pack anyway. There is NOT benefit to discharging one battery and charging the other. Why not discharge and charge the same one? Discharge and charge never happens at the same time, EDIT: and even if power were coming in (in the case of having solar panels on the roof) at the same time power was being consumed, the incoming power would simply offset the discharge by being consumed directly by the traction motor and not first taking a stop in the battery. So again, no benefit to having two batteries.

Make sense? It is a somewhat common misperception that you can charge an EV while under propulsion. I'm often asked, "why just charge while you're braking - why not also charge while you're rolling?" The simple answer - can't break the laws of physics. At this point, if it worked effectively, you'd be talking about a perpetual motion machine.
 

gadget_lover

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The swappable battery pack idea is to allow you to pull the bus into a maintenance bay after it's first 100 miles, swap batterys and do a second 100 miles while the first pack is being recharged.

The Prius HEV can (and does) charge it's battery while accelerating and while holding steady speed as well as while breaking. It does this by using excess energy from the ICE.

Unless I've totally misunderstood my electronics training, the electrons that make up electrical flow only go one direction at a time. Charging the battery moves the elctrons one direction, and running a device from the battery moves them the other way. You can't push electrons into the battery while also drawing them out.

It's neat that Napa has an electric bus. I'd like to see more of this tech, especially for runs within the city. I hate the smell of diesel.

Daniel

Daniel
 

Darell

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[ QUOTE ]
gadget_lover said:
The Prius HEV can (and does) charge it's battery while accelerating and while holding steady speed as well as while breaking. It does this by using excess energy from the ICE.

[/ QUOTE ]
Quite true... but this was in response to a BEV situation. Certainly today's HEV's get all of their electrical power originally from gasoline (since even braking regen is using the kinetic energy produced with gasoline). HEVs charge while they drive because a) they can, and b) they don't have too many other options! I think we agree that a pure BEV cannot do this, right? Or at least that it would NEVER make sense. I'm not sure I'm completely signed up with "using excess ICE energy, though. ICEs waste a LOT of energy, but there isn't any "excess" that you can really capture - with the exception of heat for the cabin. To charge the batteries, the ICE simply must work harder, and burn slightly more fuel, than it otherwise would. Otherwise, we might as well ONLY use excess ICE energy and get a free ride!

[ QUOTE ]
Unless I've totally misunderstood my electronics training, the electrons that make up electrical flow only go one direction at a time. Charging the battery moves the elctrons one direction, and running a device from the battery moves them the other way. You can't push electrons into the battery while also drawing them out.

[/ QUOTE ]
Not sure where we lost contact. We agree here completely. Did I say otherwise? EDIT: Ah, I see where the confusion was. I spoke of charging/discharging at the same time with solar - I meant using power at the same time power was coming into the system. Sorry for the confusion... you didn't really think I meant otherwise did you?! /ubbthreads/images/graemlins/eek.gif) In an EV, if you use power, the electons go one way. If you create power, the electrons move the other. They won't go both ways. But if I have solar power enter the equation, and I'm a net consumer of power, then the solar power goes directly to traction, not into the pack. If I am a net generator (say coasting or braking) then the power goes into the pack. I'm pretty sure we're all on the same page here!
 

gadget_lover

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Darell, I was not contradicting your statement, simply clarifying it for those that might have mis-understood it. I knew what you meant. /ubbthreads/images/graemlins/smile.gif

Now for the other part;
The concept of "excess" power in a ICE is an interesting one that I believe is valid.

Given:
1) An ICE produces a given amount of power at a given RPM.
2) The power by an ICE produced may be more than is needed at the moment to move a vehicle given a specific gear train.

Example; a certain fictional 350 cubic inch V8 running at 3000 RPM produces 200 HP. The engine is connected via a 3 speed transmission. When the engine is running at 3000 RPM, the car moves at 20 MPH in first gear, 40 in second and 70 in third gear.

So lets say the car is driving at 40MPH on a city street.

The car in question does not need 200 HP to maintain 40MPH on a level street, it only needs about 60HP, so it's wasting a large part of that 200 HP, right? So it upshifts to third gear and drops the engine speed to 1700 RPM, where the engine is making 110 HP. All it really needs is 60HP to overcome rolling resistance and wind resistance, but to produce a power level that low with the 350 cubic inch V8 will require an RPM down around 500.

Still with me? Does this make sense? The car is creating power that it is not using simply because it does not have a gear that will match the car's speed with the the engine's speed at the required power output. (Boy that sounded bad. Let me try again.) The lack of an appropriate gear means the engine always runs faster than it really needs to.

Enter the CVT combined with a way to split the power output between the wheels and the generator. The CVT allows a gear ratio that's close to perfect for the current conditions. The power split allows you siphon off extra power if the engine would be too inefficient at a lower speed or if you just wanted to top off the batteries.

Here's the part I'm not sure of... I'm not sure how the Prius figures out the RPM at which it wants to run the ICE. The CVT allows it to run in a wide range of speeds. It would seem to be difficult to determine the exact HP requirement at any particular moment since you can change the gearing or the engine speed or both.

What I think is happening is that the Prius chooses an engine speed that's efficient, and uses the power splitter to turn the generator at the same time as the ICE is turning the wheels. The splitter would allow the wheels to turn at the proper speed for 40MPH while the generator would turn at whatever speed it needed.

The end result? The engine effciently produces (for instance) 55 HP, where 40 goes into moving the car and 14 goes into charging the battery and 1 is wasted somewhere. When the battery is fully charged (or close enough) it shuts off the ICE and moves the car using only the battery power for a while, then starts the cycle all over again.


Why not just slow the engine so that only 40 HP is produced? I'm not sure, but I suspect that it would not be as efficient or would be more difficult to control.

Please note that this post is based on my understanding of what I see happening when I drive the Prius combined with what I've read and a small bit of guesswork about the Prius designer's thinking. I could be 100% wrong.

Daniel
 

Orion

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Okay, placing the laws of physics aside for a moment, . . . .

You have an EV that will go 100 miles on a charge [charged up that night]. The regenerative braking [and whereever else the second battery pack is being charged from] is charging the other battery during the 100 miles, while the first battery is taking the car the 100 miles on the charge the night before. Not splitting up the charging between the two, but only the one not currently being used to drive the vehicle is where I'm having a problem with seeing how it wouldn't work. Sure, more weight, but how much do these battery packs weigh, and if it is significant, will THIS technology be possible if/when they create lighter battery packs?

If the idea worked, you could drive continuously, switching out charged batteries. . . . . .

Okay, back to our precious laws of physics now. /ubbthreads/images/graemlins/blush.gif
 

Brock

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[ QUOTE ]
I'm not sure I'm completely signed up with "using excess ICE energy, though. ICEs waste a LOT of energy, but there isn't any "excess" that you can really capture - with the exception of heat for the cabin.

[/ QUOTE ]

I think what we are talking about is running the ICE as efficiently as possible. If the "sweet spot" on the ICE is 40hp at 1800rpm, and you only need 30 hp to move, then your better off using that extra 10 to charge to the batteries for later use rather then run it at 30hp where it might consume darn near the same amount of fuel.

And, yes Darell, I know on an electric motor, every RMP is the sweet spot /ubbthreads/images/graemlins/wink.gif so it makes no difference what the RPM is, heck it is even perfect for starting up huge amazingly heavy trains from a dead stop.

Orion, you understand why that doesn't make sense right? You can't possibly recapture all the power you expend. That would be like putting a wind generator on the front of your car. The drag it would create would consume about 4 to 8 times the power you would gain back in generation. It is the same sort of thing with a tire dragging to generate power. Again think of the generator on a bike it's slows you down and you have to pedal a bit more to make up for it. Using a bit more power from the first battery bank to charge the second one doesn't work.
 

gadget_lover

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Nicely said, Brock.

Back to Orion's plan...

The regen braking only captures a small amount of the energy used to get the bus rolling. The rest of the energy is used up as wind resistance, rolling resistance and other inefficiencies.

When you say "and whereever else the second battery pack is being charged from" you imply an on board generator. The generator could just as easily refresh the the first battery pack. If you are drawing power from the battery the generator's output would supplement the battety, meaning that less energy woudl be drawn from the battery.

There's no need for a second battery if you have an on board generator. A second battery would be helpful if you could swing by a maintenance center to swap it in. Look around Costco the next time you are in. Our's has a section in the back of the store where they have a spare battery on charge for the fork lift. It's huge, and has a quick connect on it.

Daniel

Daniel
 

idleprocess

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[ QUOTE ]
Orion said:
Okay, placing the laws of physics aside for a moment, . . . .

You have an EV that will go 100 miles on a charge [charged up that night]. The regenerative braking [and whereever else the second battery pack is being charged from] is charging the other battery during the 100 miles, while the first battery is taking the car the 100 miles on the charge the night before. Not splitting up the charging between the two, but only the one not currently being used to drive the vehicle is where I'm having a problem with seeing how it wouldn't work. Sure, more weight, but how much do these battery packs weigh, and if it is significant, will THIS technology be possible if/when they create lighter battery packs?

If the idea worked, you could drive continuously, switching out charged batteries. . . . . .

Okay, back to our precious laws of physics now. /ubbthreads/images/graemlins/blush.gif

[/ QUOTE ]
<ul type="square">
Here are juts a few losses in the average BEV:
[*] electrical resistance
[*] rolling resistance
[*] driveshaft friction
[*] wind resistance
[*] imperfect regenerative braking
[*] changes in direction (takes energy to change direction - energy that can't be recovered)
[*] bumps in the road
[*] ..etc...
[/list]

There have been experiments to the ends you're proposing, and they're usually referred to as perpetual motion machines. There is one concept I've heard of that has a slight chance of working... sort of.

Take a magnetic levitation sled. Put it on a perfect maglev track in a vacuum. Accelerate it on a straight section of track then decelerate it and re-capture the energy somehow. Now the only losses in the system are the acceleration system, magnetic frction, and the re-capture mechanism for deceleration... but they're losses nonetheless.
 

Darell

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[ QUOTE ]
Brock said:
[ QUOTE ]
I'm not sure I'm completely signed up with "using excess ICE energy, though. ICEs waste a LOT of energy, but there isn't any "excess" that you can really capture - with the exception of heat for the cabin.

[/ QUOTE ]

I think what we are talking about is running the ICE as efficiently as possible. If the "sweet spot" on the ICE is 40hp at 1800rpm, and you only need 30 hp to move, then your better off using that extra 10 to charge to the batteries for later use rather then run it at 30hp where it might consume darn near the same amount of fuel.

[/ QUOTE ]
Yup - gonna have to go with Brock on this one... I think. /ubbthreads/images/graemlins/smile.gif A CVT allows the ICE to run at the optimum RPM for the task at hand. I still have trouble thinking of the power used for battery charging as "excess power" but it is some gray area in there where the ICE is allowed to function at the most efficient power/RPM, and some battery charging can happen. I still say that if the battery charging never happened, that the ICE would consume less fuel overall. But if you need to charge the batteries with the ICE anyway, you might as well do it when the ICE can benefit from expending a bit more power. But hey, I'm just guessing here as well.

There is no question in my mind that the Prius does the power management better than any other ICE vehicle on the road. The Prius is a marvel of efficient engineering. I love the way the power split works mechanically and automagically. At this point, the only thing that could make the system an order of magnitude more efficient is to allow grid charging of a larger battery pack!
 

bindibadgi

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And to make the ICE a diesel so you could use some renewable fuel in it. /ubbthreads/images/graemlins/smile.gif
 

idleprocess

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[ QUOTE ]
Darell said:
There is no question in my mind that the Prius does the power management better than any other ICE vehicle on the road. The Prius is a marvel of efficient engineering. I love the way the power split works mechanically and automagically. At this point, the only thing that could make the system an order of magnitude more efficient is to allow grid charging of a larger battery pack!

[/ QUOTE ]

Given how relatively tiny that the battery pack is, I imagine that it wouldn't be that much of a challenge to substantilly increase its capacity... at the expense of warranty support and no small amount of time tinkering with the electronics/firmware, no doubt.
 

gadget_lover

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Actually, very little need be done to add a second battery pack. One person did it by adding a relay to isolate the second pack during the start-up selfcheck. The rest of the electronics and firware did fine.

I suspect that it's not easy to select the perfect RPM (and thus power outout) simply because the wind, pavement, incline and many other things change from moment to moment. If you had exactly the right HP being generated (no more, no less), the slightest breeze would slow you down. You see this with a simple cruise control and mild inclines. The speed drops as you start to climb a gentle hill, and then it overshoots as it tries to bring the revs back up again.
I'm just guessing here. I'm not a mechanical engineer.

* * * SPOILER * * *

Here's a secret about the power splitter; the CVT in the Prius is electric. Yup. The "generator" goes into motor mode to spin the planetary gear on occasion to cancel out the rotation of the ICE, effetively changing the gear ratio and even simulating neutral. At other times it exerts a known load on the planetary gear, causing the gear to rotate slower so the ratio of ICE revs to Engine revs changes. This action is why you sometimes see the ICE is running the generator to feed the electric motor.

Verrrrrry clever, No? You can see a neat demo of the concept with a java enabled browser at
http://www.wind.sannet.ne.jp/m_matsu/prius/ThsSimu/index_i18n.html



Now if they can figure out how to do this without needing to use the generator as a motor, the efficiency goes up yet again.

BTW, Darell, That's quite a complement to the Prius, coming from a guy with your dedication to enviroment friendly devices.

Daniel
 
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