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by Research groups are developing modification kits for hybrids such as the Toyota Prius to alter the computer's balance between the motors and combustion engine. Currently, the vehicles utilize the electric motors for low speed operations or to provide power assisting boosts while accelerating. At higher speeds, where combustion engines achieve better performance, the motors deactivate. By tweaking the transition period, researchers believe the hybrids will be able to utilize the electric motors at higher speeds to further improve the fuel efficiency up to 100mpg.
One side-effect of this will be an increase in electrical demands, such that a car will no longer be electrically self-sustaining and require stops to plug-in for a recharge. However, utilizing the existing power grid for recharging a car is estimated to cost an equivalent of 60 cents of electricity to match a gallon of fuel performance. Incorporating ultracapacitors and improved electric motors will make such recharging stops fewer and further between.
In light of recent cost/benefit analysis, hybrids may soon become financially viable as well.
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What I don't understand about changing your hybrid to require periodic recharging is: why not do away with the combustion engine altogether? If you're going to deal with the inconvenience of having to plug your car in overnight to use it, then why drive around with all the extra dead weight in the vehicle?
The PRIUS+ project from CalCars (link to PDF) adds extra batteries extending electric-only operation up to 34 MPH and providing extra (as compared to normal Prius battery pack) electric assist during normal hybrid drive. To get the improved "gas millage" (they also figure the cost of electricity used to recharge the batteries into this calculation) 300 lb. of batteries must be added. With lead-acid batteries used in early PRIUS+ model, this added weight gives you 10 electric-only miles. Anything past that is hybrid miles. Using Li-Ion batteries extends the all-electric millage to 35 miles. BTW, these miles also have to be at speed at or below 34 MPH.
Let's say that taking out the gas engine and supporting systems will reduce the car weight by 30%. With the same Li-Ion battery pack, the all-electric range increases to 45.5 miles (all driven at or below 34 MPH!) between recharge stops, which cripples the car's usefulness in my opinion.
To get beyond the 34 MPH limit, I image you'd need a bigger electric motor, which increases the weight. The current Prius electric motor delivers a tiny 26 HP.
Anyway, there's trade-offs and engineering compromises all over the place here depending on the expected use of the vehicle.
Trade-offs are fun. At least for Nerds. So will the evolution of the car eventually lead to user customization of the power plant? The driver could load a feul/perfomance profile into the vehicle's computer that optimized it for whatever conditions were needed. People are already doing this with mod chips that either increase horsepower or feul economy based on personal tastes.
This would be a far cry from the Henry Ford mass-production model!
Reasons for the internal combustion engine are 1. helps accelerate the car to higher speeds (where the electric engine becomes inefficient) and 2. allows for indefinate range (gas stations easy to find; place to plug your car in hard to find.
"...to further improve the fuel efficiency up to 100mpg.... One side-effect of this will be an increase in electrical demands, such that a car will no longer be electrically self-sustaining and require stops to plug-in for a recharge."
Does anyone else see the problem with calling this fuel efficiency?
No, if it gets more distance out of the gas, then it has better efficiency. It's not fuel convenient, though.
"No longer electrically self-sustaining" means that it is not getting all the extra distance out of the gas, it's getting it from the wall socket.
You've gone from a closed system, where you account for a certain amount of gas to go a certain distance, to an open system, where you have a specified amount of gas and an unspecified amount of grid-supplied electricity to go a specified distance. Under these conditions, the "100 MPG" claim is meaningless.
I'm not saying it's not a useful model for powering transportation, just that the mileage claims are spurious.
Ah, I see what you're saying now. That doesn't make sense to me either, but it seems they would be smart enough to avoid that mistake - so I investigated on EDrive's FAQ page. I didn't find a direct answer, but I found this:
Q12: How much does it cost to charge the car?
A: A full charge could take 9kWh of electricity from the wall socket, but on days when the car is driven less than 50 miles, the electricity needed to re-charge will be less. If your electricity cost $0.10/kWh (about average) then a full charge would be just under a dollar.
Thus, assuming their electricity costs to be correct, the price for a mile of commuting would be $0.02. To get the same cost from an ICE or hybrid, the price per gallon divided by the miles per gallon would need to equal this same amount. For example, given $2.50/gallon for gas, the fuel efficiency needed would be 125mpg to result in a cost of $0.02 per gallon. So, if the gas prices stay above $2.00, you'd still be paying less per mile than what you would with a car that gets 100mpg.
Assuming the power plant is running at a fuel/kWh efficiency greater than a hybrid vehicle (which is likely), the overall fuel efficiency probably fits the claimed trend.
It also sounds like this kit is a step toward blurring the lines on what type of hybrid you have. I read a Scientific American article years ago (sorry, no link) that defined a parallel hybrid as one that uses a combustion engine and electric power together to propel the vehicle (like hybrids on the market today). They also had what they called a series hybrid, in which the combustion engine powers the batteries, but does not propel the vehicle directly through a transmission.
Wikipedia seems to use different terminology: http://en.wikipedia.org/wiki/Hybrid_vehicle#Parallel
Howstuffworks had a pretty good definition of it as well: http://auto.howstuffworks.com/hybrid-car2.htm
The Prius+ package looks like it abstracts the parallel hybrid a bit by letting you use it in electric only mode like a series hybrid. This interests me because a series hybrid has some cool implications over the parallel IMO. Not just because using electricity off the grid is cheaper, as claimed by the Prius+ people, but because if the industry shifts even further to the series side they can make even better hybrids with even better mileage because series hybrids only use their combustion engines to recharge the batteries. By that, I don’t mean the temporary advantage from plugging in and not using the engine at all, but when you do go on long trips and the engine runs, the car can run the engine at its ideal and most efficient range of RPMs. Look at the torque and power curves for any engine out there and you will see the torque and power increase with rpm, but peak and start to decline. Run the engine powering a generator at that point and suck every watt the engine produces and you can handily improve the efficiency the Prius and other hybrids get now because their engines are doing most of the work when you drive and have to deal with the whole rpm regime.
My understanding of the parallel hybrids is that they, too, take advantage of a more optimal range of rpms. The electric motor runs at the low rpms, which is where the ICE is least efficient. As speed increases, the batteries are supplemented by the ICE in its optimal range. I'm not sure what this range is, though, and it's possible that it could be narrowed even further to squeeze out some efficiency.
The whole idea of electric cars is just so much better than combustion engines. If you were designing a car from scratch with the technology available today and neglecting all environment or existing infrastructure concerns, there is no way you would pick an ICE over an electric motor. Why have a million tiny power plants running with all of the problems and maintenance that come along with them when you can have ONE stationary large power plant running at optimal levels 24/7?
Of course the issue now is more complicated because you have those environment and infrastructure concerns - but part of me thinks that if I was making the decisions I would rather make a new infrastructure than coddle the existing defective one.
The problem is batteries and their power to weight ratio. And expense.
I forgot to mention another reason I am keen on the whole series hybrid concept. Performance. The original GM electric car had pancake electric motors to propel it that were in the wheel. Around the same timeframe I first heard about this stuff, all wheel drive was becoming really popular for performance cars (around 1990), like the Porsche 959, the Audis, Eagle Talon, etc. Back then I was imagining what you could do if you made a series hybrid with one electric motor per wheel... The problem with conventional all wheel drive is the weight, mechanical complexity and poor efficiency. With all electric drive, you can do it by routing a power cable. Electric motors have high torque at low speeds, so you could really launch off the line--oh, by the way, without really denting your efficiency unless you have tire slip.
Lotus also was working on Active Suspension back then too, but it was all hydraulic. Add an active suspension using linear electric motors and you could build a really killer car which would behave and get good economy.
It's funny that you mention pancake electric motors. My senior year at Texas A&M University as a Mechanical Engineering student, our senior design class project was to design a Mars Rover - and we powered it with pancake electric motors, one inside each wheel. I don't see any reason why that wouldn't work on Earth-bound vehicles. There would still need to be some secondary systems (A/C, suspension, etc.), but the design as a whole would be a lot simpler - no transmission, very short drive trains, etc.
One of the major issues restricting the range on the hybrid and electric only vehicles is that manufacturers are still using a 12V system. When you take the energy demands of current vehicles: electric locks, windows, A/C, stereos, lighting and instrumentation that 12 volts will only go so far. Toyota, Honda, Ford and GM are all looking at increase the voltage sytsem in vehicles but with that is the increased cost of new accessory systems as well and the replacement parts. Though it is cost efficient in the long run, the initial cost has hindered the implementation of a 60 volt system.
If a higher voltage system was implemented and a deeper cycling batter system, the electric side could be used longer. Once the battery charge had dropped below it's efficient threshhold, it could be shut down allowing a passive charging system within the drivetrain for recharging. With the addition of a small but efficient wind powered generator using ducted air from the underbody not only could you increase the vehicle's stability at higher speeds but depending on design would also minimally impact drag.
Well, voltage shouldn't be too much of a problem if the vehicle used AC because you could just have a transformer to boost the voltage for the components that require it as they gradually transition to the higher voltage components. Boosting DC system voltage would be a little more complicated unless you connect a bunch of batteries together. The electrical components in most cars are DC.
I'm not so sure voltage is really the issue here, but power. You can still get the same power with 12V, but you have to push more amps to do it. If one battery won't do the trick, maybe you could have an auxiliary deep cycle battery to run accessories and have the regular battery solely for starting the engine, lights, etc. Or you could have a pack of deep cycle batteries to get the 60 volts you want (or a purpose built 60 volt battery, which gets you the same results as a pack of regular batteries, batteries are nothing but a pack of cells).
Deep cycle batteries have longer, shallower discharge curves than regular car batteries. For example, my boat has a deep cycle for the trolling motor, but a regular battery to start the engine. The deep cycle doesn't have the amps to push out in a short time to feed the starter, but it can push out a lot of amps over a longer time than the starter battery does and can tolerate being discharged and carry a load further without damaging it. The only trick here would be to safeguard the alternator from overloading when recharging the batteries. The electronics to monitor the battery and the altenator and control the charge accordingly.
I think regenerative braking would be a good source for the charging, but I don't really like the idea of the wind turbine. The wind is generated by work performed by the engine anyway, so why not link directly to the engine? Braking converts the car's kinetic energy into heat and wastes it anyway, so recovering that loss is one of the easiest ways to improve automotive efficiency and is probably the primary way hybrids make their gains. How much of the time does the average person drive their cars at speeds high enough to make something like a wind turbine to work? If you make it to work at low speeds, how do you keep it from getting torn up at higher speeds? This is a real problem with wind turbine operators, who have to shut their turbines down if the wind speed is above the tolerances for their turbine and is one of the design tradeoffs that they have to live with. Design it too robust, and it will be too bulky and have too much inertia to catch low speed wind and sap performance at the average wind speed, design it too light, and it will catch the faint winds and average winds well, but get torn up at higher than average wind speeds.
Yes, you are correct. People don’t realize the impact full hybrids have on how cars are build. These are electric cars with gas engine supports. In this case, the Heater, A/C and power steering are all electric. This allows these modules to be placed anywhere in the car, and in any brand car. Since they are high power devices, they cannot use 12V. I am sure companies like Bosch are working on much higher voltage systems, since hybrids open the market to standardize all car appliances. So will it be AC or DC? Why not 240V 50 Hz? As an electrical engineer, I would like to see 2Khz at around 250V. My Highlander already uses 580V 3 phase motors, and a 240V battery. I don’t know what the A/C–Heater uses, but it is a large red cable, indicating > 48VDC.
Urs
I'm curious why you would like to see 2KHz and 250V. I'm more on the mechanical side of things and don't recall the frequency of the AC or even the voltage being as important as the wattage (P=V*A). I know that higher voltages and lower amps has more efficiency over long transmission distances. We really didn't get into electric motors as much as I would've liked, so I am keen to see what you have to say on the matter to enlighten me on this.
Hi
In a car, we want to minimize weight, and reduce energy losses on source, the transmission and user side. On the transmission side, we would like lots of voltage with very little current, which will keep the copper down to a minimum. The limit there is the insulation (safety), and interconnections. On the user side, we have users requiring low V and high A such as glass heaters, and high V with low A such as HID lights (discharge). Most other users such as small AC motors, A/C and other electronics, if re-designed, would also benefit from high V and low A. Traditionally we used transformers for this. They used iron to couple the magnetic flux between the winding, limiting the frequency to below 70hz. Having much better magnetic materials, we build DC/DC converters. These devices, ‘chop’ the incoming voltage into the highest frequency the transformer is rated for, reducing its size and weight by many times while having an even better efficiency vs. a line transformer. Using 2Khz we could use again a simple transformer directly to drive low V high A applications. On the generation side, we always convert mechanical rotation energy into electrical energy. This produces a multi phase variable frequency signal. This then must be rectified and regulated. There are no additional losses to regulate this to a constant frequency and voltage signal.
All these new power concepts, invasion one common always-powered ring line, servicing all energy users on a car. This path must be able to carry around 10kW to 50kW. To make this work, there is also a broadband data path communicating with each user, telling him to how to behave. The last word is not written yet, if this path is physically the same as the power path, or a separate control line.
I am sure we are only 3 to 5 years away, from cars with no wiring harness. I am sure, integrated power / control devices for this, will be the next ‘big thing’ in the electronic industry. In addition, the current proprietary firmware will be elevated to user-friendly software with many vendors (Microsoft) mingling.
Urs
Thank you for the concise and informative run down. I am glad to tell you I learned some valuable things from that and it gave me some things to think about.
One of my little dreams is to build my own vehicle from scratch (well, from parts--I'm not going to forge connecting rods or design and create my own integrated circuits or anything!). My dream is to make the drive train and everything electrically driven, like a serial hybrid. My reasons are basically that you can get fantastic performance with great efficiency. For example, four wheel drive or all wheel drive today is mechanically and energetically costly. Having electric motors independantly driving each wheel would be a great way to do it. You could also do tricks you can't with a car, like pivot turns in place.
I hadn't thought about insulation being a factor, or some of the other reasons you mentioned for high voltage/low current being desireable, nor why the frequency was so important. Great explanation!
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Warranties and Batteries by PowerPointSamurai :: NR7 :: on 16 November 2005
IIRC, CNN had something on people doing this a while back and Toyota and Honda strongly discouraged it. That is to say, they will probably void your warranty. I agree with the people doing it, but the one thing I would worry about is that it will cut the life of the batteries (which will not be covered by warranty now) and I will have to pony up for a new car or battery replacements prematurely.
RE: Warranties and Batteries by Brandon :: NR9 :: on 16 November 2005
I've also read about this before. I found a concept Prius plug-in online that is supposed to get 125 mpg. There's a company in California that is going to start doing the conversions - it also claims over 100mpg for the converted Prius+.
Taking a look at my hybrid article, given this increase in gas mileage, the ~110mpg converted Prius would need to be cheaper than $14,800 to save you more money than the leading economy car, assuming gas prices stay at about $2.50. If they go up to $3.00, it would need to be cheaper than about $15,200. Dang, that graph is handy.
RE: Warranties and Batteries by PowerPointSamurai :: NR7 :: on 16 November 2005
Yeah, I read your article both here and the commentary it generated on Slashdot. In typical Slashdot fashion, the responses ranged from constructive and insightful from well informed people to crazy rants from self-righteous wanna be's that think they are smart. Anyway, I think the hybrid upgrades are cool as hell in their own right from an engineering standpoint even if it doesn't meet the cost analysis, which is exacerbated by the battery issue if you cut your battery life and have to prematurely replace them. Still, there is something to be said for saving energy even if it doesn't save you money right this second.
RE: Warranties and Batteries by Brandon :: NR9 :: on 16 November 2005
Right, the issue is much more complicated than just my what my article covers, but at least I now have one good resource to use when looking at the hybrid/no-hybrid enigma - something I can realistically see myself doing over and over as gas prices, hybrid prices, and fuel efficiency continue to change.
Look at me, tooting my own horn... It must be backlash from reading some of those "crazy rants from self-righteous wannabes that think they are smart." :)
RE: Warranties and Batteries by TMKelley :: NR0 :: on 17 November 2005
Which is worse for the environment? The miniscule extra amount of pollutants that would have been released into the atmosphere by choosing a Toyota Camry over Prius, or the 300 pounds of batteries that will eventually end up in a landfill?
RE: Warranties and Batteries by Brandon :: NR9 :: on 17 November 2005
I'm not sure where this comment came from, but I've heard the point before. I wonder, though, how certain are you that the batteries are landfill bound? If they were, what would be the severity of the environmental impact? Until I get some hard data, I'm not going to pull a skeptic and "suspend judgement."
RE: Warranties and Batteries by PowerPointSamurai :: NR7 :: on 17 November 2005
This came up several times on the Slashdot discussion on this article and was repeatedly put to bed with two points. 1) The batteries on the Prius are NiMH, not lead acid batteries. These batteries are far less damaging to the environment if you chuck them in a landfill than NiCd or lead acid batteries, and moreover, are easily recyclable and have mineral components that make them well worth recycling. 2) That Toyota offers something like a $200 bounty for used Prius batteries for recycling, which suggests that they really are worth recycling and they want them back, or at least Toyota realizes that their customers are concerned about the environment (because they bought the hybrid in the first place) and are savvy enough to assauge their concerns about the batteries being an environmental hazard.