Electric & Alt Fuel Vehicles, Part 3

[dukeleto]

Slightly OT, but just intrigued:

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idleprocess said:

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

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<ul type="square">[*] changes in direction (takes energy to change direction - energy that can't be recovered)
[/list]


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Are you sure of that? I would have thought it requires a force, but not necessarily energy:
if you apply a force perpendicular to your direction of motion you should change the direction, but since it's perpendicular to your motion, the power is 0 (I think)

 

[Orion]

Wow. I guess I am just a little clueless on the whole physics of it. It SEEMS logical to my mind, barring the laws of physics, . . . . . . . I guess I'm simple in the way I look at it. Take, for instance, a cordless drill. While using the one battery, the other charges, so that when the first runs low, you switch out the battery with the fresh one and let the drained battery charge. I guess when it comes to doing this in a vehicle, charging the drained battery takes more energy.

How about this. Now please bare with me/entertain the notion/amuse me/be kind regardless of my ignorance /ubbthreads/images/graemlins/smile.gif. Rather than using regenerative braking to charge the second battery, you have a very small ICE [like from a scooter or something]. Something that gets like 100 mpg. Let IT charge the battery using a series of generators. Similar to the Hybrid [in a very small way], but all the power comes from the electric motor.

Yeah, I'm reaching. I just wish they'd increase the distance between charges. The distance currently would be fine for in town, but going on a long trip on vacation would be problematic, especially given our current energy setup.

I'm with you all on this. I wish we would quit relying on foreign oil [heck, even domestic oil] and start using more environmentally friendly means to power things.

This is a great topic, by the way!! /ubbthreads/images/graemlins/smile.gif

 

[jtr1962]

[ QUOTE ]
idleprocess said:
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.

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Actually, there's a serious proposal to build one of these running across the Atlantic Ocean. It would travel at speeds of up to 2300 mph and make the trip in only a bit over 1.5 hours. Compare this to the eight or nine it takes by plane now once you count the journey to the airports. Actually, we'll probably have to travel long distances like this once the oil runs low for the simple reason that planes have no alternative to fossil fuel whereas electricity to power maglevs can come from plenty of non-fossil fuel sources. This isn't a perpetual motion machine be any stretch, but if you recapture most of the kinetic energy while braking it will use far less energy per passenger mile than any other form of transport. Maglevs do have a magnetic drag of sorts, but this is only a pound or two per ton of mass.

 

[Darell]

[ QUOTE ]
idleprocess said:
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.

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Yes... as Daniel points out, this is already being done. I am aware of two separate groups who are seriously trying to market a viable "Plug in" kit for the Prius. Tests so far are revealing 100-120mpg with appropriate control and about 3x the battery. And of course short trips are pure BEV. THAT's the second car I need! Would have been so simple for Toyota to make it that way in the first place, but what're ya gonna do? Do it yourself, that's what!

 

[jtr1962]

[ QUOTE ]
Orion said:
Yeah, I'm reaching. I just wish they'd increase the distance between charges. The distance currently would be fine for in town, but going on a long trip on vacation would be problematic, especially given our current energy setup.


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To answer your earlier question, yes it does take energy to change direction even though you're going the same speed. This extra energy manifests itself in the form of increased resistance on curves. It exists because a change of direction is in fact an acceleration, and acceleration takes energy.

Now you talk about increasing range and I agree. Let's start with the basic equation for land vehicles, R (resistance) = A + B*speed + C*speed². The first term is static rolling resistance. The second term, which is proportional to velocity, is a combination of laminar air drag, tire flexing, and bearing drag. The third term is aerodynamic drag.

For a car if we want the resistance in pounds the equation is R = 0.01*weight + 0.0001*weight*speed + 0.0024*Cd*frontal area*speed². Frontal area is in square feet and weight is in pounds. Low-rolling resistance tires might cut the first two terms by up to 50%, but as you can see the heart of the problem is the third term. For a 2 ton car at 75 mph the sum of the first two terms is 70 pounds. However, let's look at that third term. For a large, boxy SUV we might have a frontal area of 35 ft² and a Cd of maybe 0.6. This gives us an aerodynamic drag of 283.5 pounds at 75 mph, over four times the magnitude of the tire drag. Total drag is 353.5 pounds and we need 353.5*75/375 or 70.7 HP to maintain a constant 75 mph. Now let's take Darell's former EV1. It probably has low rolling resistance tires and weighs 3000 pounds. Therefore, the first two terms might be ~37 pounds at 75 mph (let's assume the tires cut rolling resistance by 30% over regular tires). The frontal area is much smaller, maybe 22 ft², and I think he said the drag coefficient was 0.15. Therefore we have aero drag of 44.6 lbs at 75 mph and total drag of 81.6 pounds, only 23% of what is needed by the SUV. Total HP needed is only 16.3 instead of 70.7. Bingo, for a given battery pack you have over four times the range.

We can do even better than the EV1 in terms of Cd and rolling resistance. Perhaps we can design vehicles needing only 7 or 8 HP to maintain 75 mph. That's the key here. We need to get away large and especially boxy vehicles regardless of power source if we want to deliver better energy efficiency. Maybe it's just me but it seems Detroit forgot whatever lessons they learned about aerodynamics in the last ten years. Maybe we need legislation mandating maximum drag coefficients rather than just fuel economy. Or better yet, measure efficiency in terms of KW-hr per mile regardless of power source.

 

[Darell]

[ QUOTE ]
gadget_lover said:
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.

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We've found that the only real limitation on the existing controller is that you can't drive in pure BEV mode faster than 35mph. Several reasons for this, apparently, but most are due to the small battery size... Tough one to get around, apparently. /ubbthreads/images/graemlins/frown.gif

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http://www.wind.sannet.ne.jp/m_matsu/prius/ThsSimu/index_i18n.html

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This thing is GREAT! I've seen similar ones before, but now ones that let me drive it manually.


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

[/ QUOTE ]Hey, I know how I often come off sounding like doing it MY WAY is the only way. I'm usually so focussed on getting a specific message across, that I forget to cheer for everybody else who's on the same team. We're all here because we care, and I think that's awesome. Besides driving less, driving a small diesel, a hybrid or an underpowered little ICE - there are few other choices we have to save burning fossil fuels for our transportation needs. Hybrid drivers are doing what they can with the resources availble to them. And I have nothing but respect for that. It only saddnes me that we have no other choice but ICE vehicles in this country.

As Bindi pointed out above, there is certainly more that can be done with existing ICE/hybrid technology to improve our situation... and we seem to be moving at a snail's pace. Why we don't have plug-in hybrids is simply beyond me. I mean, they're spending money to advertise the fact that we can't plug them in, when it would benefit everybody if we could... with the added situation where you would never actually HAVE to plug it in, if you were silly enough to think that going to the fueling station was more convenient than plugging it in. /ubbthreads/images/graemlins/icon23.gif

OK, so back to my point - I sometimes forget to stop and appreciate what others are doing toward the same goal that I have.

 

[Darell]

[ QUOTE ]
Orion said:
Wow. I guess I am just a little clueless on the whole physics of it.

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Hey, I'm just happy that you're interested enough to keep plugging away at it, and to not get discouraged or to tell the rest of the population that it isn't thinking right! /ubbthreads/images/graemlins/smile.gif

OK, I'll take another stab at this one...

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Take, for instance, a cordless drill. While using the one battery, the other charges, so that when the first runs low, you switch out the battery with the fresh one and let the drained battery charge. I guess when it comes to doing this in a vehicle, charging the drained battery takes more energy.

[/ QUOTE ]
What you're saying *could* happen with an EV. The battery charges OFF the vehicle. To put it in your terms, pretend your drill has one battery in place to power the drill, and the other is rubber-banded onto the side of the thing. How is that second battery helping you? How are you charging it while you use the other battery? The only way it is getting charged is when it sits in the charger. Let's say the drill had regen brakes - it would still make more sense to put that power BACK into the pack that is snapped in instead of figure a way to get that power out to the second battery that is flapping in the breeze. I'll expand on this a bit more after the next comment...

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How about this. Now please bare with me/entertain the notion/amuse me/be kind regardless of my ignorance /ubbthreads/images/graemlins/smile.gif. Rather than using regenerative braking to charge the second battery, you have a very small ICE [like from a scooter or something]. Something that gets like 100 mpg. Let IT charge the battery using a series of generators. Similar to the Hybrid [in a very small way], but all the power comes from the electric motor.

Yeah, I'm reaching. I just wish they'd increase the distance between charges. The distance currently would be fine for in town, but going on a long trip on vacation would be problematic, especially given our current energy setup.

[/ QUOTE ]
OK, let's try this way, and hope it makes some sense. You want a second battery to recapture whatever charge you may have. You see the first battery as offering 100 miles of range, and then once you've added a bit of charge to the second battery, you could drive some more miles by switching to it. We on the same page so far? Here comes the secret - why you don't need that second battery. While you drive along, draining your first 100 mile battery, you are leaving room in that battery to accept more charge. So after you've driven 50 miles, you have half your charge in that first battery. We still together? Now the secret: You've driven 50 miles without ever braking (so no charging has happened, even to the theoretical second battery) - but now you go down a huge hill, and use the regen. What happens now, is you put charge BACK into the primary battery. You fill it back up. Let's say you fill it up 25% from your braking adventure. Now, that very same primary pack will take you the 50% it had before braking, plus the extra 25% that you just added to it! Now your range has increased from 100 miles to a total of 125! Extra battery pack NOT NEEDED! Sure, you COULD have stuffed the regen into a second pack, but there is absolutely no reason to do so. You simply discharge and recharge the same pack as you drive. The ONLY time this does not work is if you want regen when the pack is 100% full. But just drive a few miles, and you've left enough room to capture quite a bit of braking, trust me! It has been considered to swap charged packs out at service stations like in your drill example. But you still only carry one pack at a time. You drive until you deplete your pack, and then swap for a charged one, just like the drill. But the ONLY way two packs in the car make sense is if you start with both of them charged - as if you had one pack twice the size. The ONE pack is all you need to recapture any regeneration that comes your way.

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I'm with you all on this. I wish we would quit relying on foreign oil [heck, even domestic oil] and start using more environmentally friendly means to power things.

This is a great topic, by the way!! /ubbthreads/images/graemlins/smile.gif

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Here, here!

 

[evan9162]

[ QUOTE ]
Darell said:
[ QUOTE ]
idleprocess said:
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.

[/ QUOTE ]
Yes... as Daniel points out, this is already being done. I am aware of two separate groups who are seriously trying to market a viable "Plug in" kit for the Prius. Tests so far are revealing 100-120mpg with appropriate control and about 3x the battery. And of course short trips are pure BEV. THAT's the second car I need! Would have been so simple for Toyota to make it that way in the first place, but what're ya gonna do? Do it yourself, that's what!

[/ QUOTE ]

I was thinking about this the other day. My bet is that Toyota had to balance the size of the battery with gains in fuel economy, size/weight of the pack, cost of the pack, and availablility of the pack. It would be nice if they offered an option of doubling the battery size.

Maybe they didn't due to physical design constraints (i.e. where to put the second one), and availability (I order a double pack in a Prius, and supplies are tight, then that's one less Prius that can be delivered somewhere else).

 

[Darell]

[ QUOTE ]
evan9162 said:
I was thinking about this the other day. My bet is that Toyota had to balance the size of the battery with gains in fuel economy, size/weight of the pack, cost of the pack, and availablility of the pack. It would be nice if they offered an option of doubling the battery size.

[/ QUOTE ]I'll bet those are all strong contenders for the decision. Toyota seems dead-set against having people grid-charge these things, so there's really no reason for a bigger battery at this point. The bigger question in my mind, is why doesn't Toyota want us to grid-charge them? We call that "gas optional" and I see no downside - even with the existing size of the battery pack!

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Maybe they didn't due to physical design constraints (i.e. where to put the second one)

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Yeah, I'm not buying this one. We're finding plenty of places for extra batteries in the existing configuration. If larger batteries were designed in, it would be even easier. There is even an empty shelf that fits a second battery right under the trunk floor already. Availability and price, maybe. Physical constraints, not so much.

 

[evan9162]

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Darell said:
I'll bet those are all strong contenders for the decision. Toyota seems dead-set against having people grid-charge these things, so there's really no reason for a bigger battery at this point. The bigger question in my mind, is why doesn't Toyota want us to grid-charge them? We call that "gas optional" and I see no downside - even with the existing size of the battery pack!


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I wonder if the Prius could be considered by some to be an EV at that point (by a stretch of the definition) - at which point they'd be under the gun for getting licensing to use NiMH batteries in an EV from Texaco. I could see that happening - people have stretched the definition of their IP more than that before.

 

[Darell]

[ QUOTE ]
evan9162 said:
I wonder if the Prius could be considered by some to be an EV at that point (by a stretch of the definition) - at which point they'd be under the gun for getting licensing to use NiMH batteries in an EV from Texaco. I could see that happening - people have stretched the definition of their IP more than that before.

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Yup... that's sort of what I was getting at without wanting to sound like a conspiracy nut...

The general assumption is that automobiles are designed to be the best they can be - give the buyers what they want and all that. Turns out that it's a wee bit more complicated than that!

 

[Orion]

Stepping in to say thanks to Darell and all else who helped me try to understand why my thinking wouldn't really work. I guess that's what I get when I don't take any physics classes. /ubbthreads/images/graemlins/blush.gif . . . . . Of course, I am still going to *attempt* to build a perpetual motion machine, though the laws of physics are against me. I will TRY!!!. . . . . .

Anyway, about the Prius, until they come out with a production EV, I guess the Prius is on top of the green vehicles.

 

[Brock]

What are the D and B on the Prius? I assume the D is drive, taking a stab at the B, battery mode, but what exactly is that and what does it do differently? More aggressive generator braking? The more I learn about this car the more I like it. Again my commute is 42mph for 20 miles with 1 stop sign, so the regen wouldn't do me much good on my trip, now triple the battery pack and let it run even 40mph on battery with the ability to grid charge and I am good to go.

 

[Darell]

[ QUOTE ]
Brock said:
What are the D and B on the Prius? I assume the D is drive, taking a stab at the B, battery mode, but what exactly is that and what does it do differently? More aggressive generator braking?

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As far as I know, the B is the same as it is on the Rav4EV. It is regenerative braking. If you want to slow down, or hold the car back going down a long hill, you use B and it is pure regen with no friction brakes.

Seen in the Rav here, just below D: http://www.darelldd.com/ev/images/rav/rav_mods/rav_wheelskin.jpg

 

[evan9162]

From what I understand, B means engine breaking, it keeps the engine running so you can use the engine to hold you back as you travel down a very long hill. Normally the Prius shuts off the engine when coasting or slowing down, and B mode prevents that from happening.

 

[Brock]

Ok, but why would you not use B all the time? As soon as you let up on the go pedal it would start to slow down and generate. Is there a down side to that?

So the "D" more or less "free wheels it" when you let up on the go pedal and the "B" slows it down via generation depending on how much you let up on the go pedal?

Daniel what do you run it in and why?

Darell what do you run the RAV in?

 

[Orion]

I think the B is used when you are going down hill. Acts as an engine brake, like downshifting a conventional transmission.

 

[Darell]

[ QUOTE ]
Brock said:
Ok, but why would you not use B all the time? As soon as you let up on the go pedal it would start to slow down and generate. Is there a down side to that?

[/ QUOTE ]
Yes! You don't always want to slow down ever time you come off the go pedal. Coasting is a wonderful thing that EVs do better than any other vehicle. The goal is a consistent speed, so always accelerating or slowing is not desirable. Think about how often you come off the go pedal without wanting to actively brake.

[ QUOTE ]
Darell what do you run the RAV in?

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Always in D, and shift into B when I need it, then back to D for normal driving. I have two levels of regen in the Rav. The light regen is on the shifter, the heavy regen is B. The light is to mimic how a gas car slows under engine compression. Using the two judiciously can mean almost never having to use the brakes.

 

[Darell]

[ QUOTE ]
evan9162 said:
From what I understand, B means engine breaking, it keeps the engine running so you can use the engine to hold you back as you travel down a very long hill. Normally the Prius shuts off the engine when coasting or slowing down, and B mode prevents that from happening.

[/ QUOTE ]
Man, I sure hope not. If this vehicle specifically uses the ICE to throw away kinetic energy, I'll eat my shorts. The whole point of having the battery is to recapture the kinetic energy from braking, and reuse it to accelerate. If the ICE is spun under compression to throw it all away, it is time to start over. /ubbthreads/images/graemlins/frown.gif

 

[evan9162]

[ QUOTE ]
Darell said:
[ QUOTE ]
evan9162 said:
From what I understand, B means engine breaking, it keeps the engine running so you can use the engine to hold you back as you travel down a very long hill. Normally the Prius shuts off the engine when coasting or slowing down, and B mode prevents that from happening.

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Man, I sure hope not. If this vehicle specifically uses the ICE to throw away kinetic energy, I'll eat my shorts. The whole point of having the battery is to recapture the kinetic energy from braking, and reuse it to accelerate. If the ICE is spun under compression to throw it all away, it is time to start over. /ubbthreads/images/graemlins/frown.gif

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This is from John1701a, probably the web's biggest advocate of the Prius, from his prius users' guide:

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The "B" mode works like a "Jake-Brake" on a large truck (except, it's totally silent). The engine is used to slow down the vehicle, allowing you to reduce reliance on the regular brakes. So for steep declines, like driving down a mountain, it's a great way to avoid overheating caused by friction from the brake drums & shoes. You can engage or disengage engine-braking at anytime while driving. There is no charging benefit over regular braking. Avoid using this mode unless absolutely necessary, since it will cause MPG to drop.


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Better have some good soup with your shorts.

Besides...once the battery is completely charged, you're just burning up the extra energy as heat anyways.