Self Sustained Power?

Discussion in 'Off-topic Zone' started by Deadman_ny, Jun 16, 2008.

  1. Deadman_ny

    Deadman_ny Spaceman

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    A few years ago when I was 14 or so I bought a small power inverter. It was only 120 watts and I never really had a use for it until one day during a snow storm our power went out. Bord I remembered the little inverter and thought... I hooked it up to an old car battery that was in the Gage and was able to run a lamp with a 40 Watt bulb and my TV and was able to watch television for a couple of hours before the car battery lost power.

    About four years ago I was stuck on a job site with no power. I had 18v Dewalt cordless drills so I was able to work but eventually after a few hours the batteries would die and I would have no way to drill holes for the wiring I was running for the house. And since the job site was well over an hour from my home I wanted to get as many hours in every day to make the trip worth while and I had a deadline to meet so the other crews could do their work. When at Walmart I walked passed the car care isle. I picked up a small 700 watt power inverter and went to the local junk yard and picked up a couple of salvaged car batteries. I brought the batteries home and charged them. The following Monday after lugging the batteries up the four flights of stairs and hooking the batteries in series (hopefully so they'd last longer) I connected the inverter up and plugged the Dewalt charger in to recharge the first 18v battery that went dead. It was sweet. I was able to work from dawn to dusk and keep the batteries charged as I worked and even attach a work light and a radio up to help with the boredom.

    Since them I bought a 5,500 watt gas generator and it worked great, but it wasn't always practical to lug it along all the time for short jobs. I then purchased a 3,000 watt power inverter for such things as running a jackhammer or floodlights and was more then pleased. I'd often just run it right off my truck battery for these short jobs. I'd have to either leave the car running or start the truck when I heard the warning chirp from the inverter warning me that the voltage was dropping too low to start my car... Great feature otherwise I'd be stranded.

    It's late and I'm bored but I was wondering. Is it possible to set up an alternator to a small motor. Most modern alternators have built in power regulators to prevent overcharging the battery.
    Allot of you guys come from different walks and I admit that I suck at math and pulleys and such are out of my scope. I'm not sure if it would be more efficient to run the motor off the inverter or the battery. My thought would be it would be difficult to find a strong enough and reliable enough 12v motor. So I'm thinking a 1/2 HP motor running off 120v would be more reliable though I'm going to lose a few watts off the inverter. And if you adjust the size of the pulleys the motor won't have to work as hard to turn the alternator and produce power. And if the alternator is working hard to keep the batteries charged it's going to require more torque and at the same time run at high enough rpm.

    Next is an alternator. I need to find one strong enough to keep the battery charged even if I'm drawing the full 3,000 watts off the inverter. I'm not sure of what the requirements are. Though there is a formula for figuring out how many volts/amps are needed from the battery supply depending on how much draw you are using on the inverter.

    Can you see what I'm trying to do here? The inverter in general wouldn't be practical for long term home use since it doesn't produce a "pure sign" and the inverter itself would produce interference. But for a job site or just out camping, power failure or whatnot it's nice to have. Extended use (days on end) I'd imagine would burn the inverter out.

    I don't want to go out and just buy a motor and alternator. I'm looking for ideas on how big of a motor and alternator along with the what size pulleys to use on the alternator and motor to make it efficient. And since the size pulleys can determine the rpm's... It's a bit confusing to me to say the least and this idea has been rattling around in my head for over a year now.

    Advice would be cool. :) Here's a pic of a similar power inverter. [​IMG]
     
  2. Andrewas

    Andrewas Rear Admiral

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    Heres the problem - every energy conversion is less than 100% efficient. Turn electricity into kinetic with the motor, and you get less energy out than you put in. Turn kinetic into electric with the alternator, and again, you get less out than in. Just run your tools off the battery or generator and you will get more life out of them than trying to use a motor to run an alternator to charge the battery that powers the motor.
     
  3. Frosty

    Frosty a full fledged GF

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    I've read your post four times and I have no idea what you're asking, but I'm going to follow Andrewas' cue and assume you're attempting to break the second law of thermodynamics. Stop trying now.

    You can't rig up a contraption that will effectively recharge the battery that powers it, and you never will. The addition of energy from outside the system is constantly necessary and defeats the purpose of having tried in the first place.

    The best solution to working away from available grid power is simply to have the most efficient generator you can find and run it on the cheapest fuel you've got locally. If there was a better way, everybody would already be doing it.


    If your question was about something else you'll have to clarify it, since I can't be sure what you're asking right now.

    Also: automotive batteries aren't really meant to be deep-cycled, and it probably shortens their life considerably to run them until the voltage buzzer alerts you. I wouldn't do it to a battery I still needed to use for one of my cars. On the other hand, the alternator can probably handle it when you let the car run, but in such cases it seems like that would be more expensive in terms of fuel than it necessarily has to be.
     
  4. Deadman_ny

    Deadman_ny Spaceman

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    I see what you mean Andrewas. And you make a very good point.

    As for the type of battery used Frosty. Aside from when I bought those batteries from the junk yard I only use deep cycle Marine batteries in my cars. Since as you said a typical battery would simply be ruined after continued draw down and recharge (zero point). Even with the best battery charger out there. Marine batteries IMHO are much more reliable in the weather conditions of upstate New York though they can cost a little more.

    Most jobs I used my gas powered generator. But the reason I invested in 3,000 watt inverters was it wasn't worth the trouble allot of times to lug a large generator around when a power supply was only needed for short periods such as using a gas powered demolition saw to cut a concrete slab and then the 30 minutes it would take to use an electric jackhammer to break it out for trenching. Or when putting modular homes together. Using an electric impact gun to take the tongue, tires, and axles off or put them on. In cases like that you don't have to leave the truck running since the draw off the battery isn't as great.

    The noise factor from the gas generator is there too. My generators are great for long term use since 5 gallons would last 12 hours or so depending on draw. But as I said before if it was a long term job I would bring a gas generator along with a tool trailer since leaving a car running is very inefficient and it's added wear and tear on your vehicle.

    It's been rattling inside my head for some time now and I was curios if t was at all possible. Not for long term use mind you but for simple things as camping and small jobs. I have talked to truck drivers and they have told me that inverters can be very useful. My second inverter I bought at truck stop. Those are tractor trailers however. Solar panels I've seen can charge the system, but that's not meant for constant use since you have to give the panels time to charge the batteries. My friend uses a similar solar/inverter system at his cabin for lights. But the energy requirements of running a few light bulbs and equipment that draws several amps... He gets allot more time off of his system for obvious reasons.

    I guess the question now is if the motor draw was small enough and the pulley's sized rite would the time of use for the inverter be increased? My "thinking" was this Andrewas; all the lights and ignition systems on a car run mainly off the alternator and not the battery. Aside from the the initial crank needed for the starter. The alternator supplies enough power to run the electronics and keep the battery charged at the same time, but the engine is an external power source. We've all jumped someone with a dead battery (with 3 sisters I've done this a bit) and you can hear your engines idle change to provide more torque to the alternator when you connect the cables. So the motor, no matter how well geared to the alternator would have to be working hard and drawing power from the inverter and in turn the battery/batteries to sustain it's own load let alone a second or third load on the inverter and in turn the battery. So the alternators output would have to have a high enough output to sustain this alone but because there isn't an external the battery would eventually lose voltage even if just powering the motor/alternator. There would be a steady drop in the initial power source regardless until the voltage drooped enough where the entire system failed. Once the battery amps/volts drops below what is required to start a car is met the inverter will turn off. Even if the alternator is able to sustain this minimal level any additional load would cause failure.

    Makes sense but would this system increase the available run time of the inverter at least? Since the alternator would be able to (in theory) supply some volts/amps to sustain the system and instead of just drawing directly off the battery the decline of power wouldn't be nearly as sudden.
     
  5. ELTEE

    ELTEE Rear Admiral

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    No, no, no, here's what to do. I think you should go and rescue 4,325 hampsters. Then, go to the junkyard and get a bunck of beat up bicycle rims. Use an old car battery to shock those critters into running real fast, and install some friction motors with the rims. No noise, no fuel, but definitely some entertainment on the job site!

    If I was all forum and tech savvy, I'd go ahead and post some pictures of hamsters below for reference, to ensure the proper equipment is acquired.
     
  6. Nomad Terror

    Nomad Terror Rear Admiral

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    I'm pretty confused here, too.

    A car alternator can keep the car's electrical system working and the battery charged because it is being turned by the engine. The engine is being powered by internal fuel combustion, not by the electrical system.

    Let's take the simplest perpetual machine concept. A battery that powers a DC motor which spins an alternator which sends current back into the battery. The first law of thermodynamics states that in any process, the total sum of energy remains the same. No matter how efficient you make your machine, there will be energy lost. Wires are inefficient conductors and have some degree of insulation (energy will be lost as heat), the DC motor has spinning components which have friction (energy will be lost as heat), the chain, belt or shaft which will turn the alternator will suffer friction (energy will be lost as heat) and the spinning mechanism of the alternator will suffer friction (energy will be lost as heat).

    It is impossible for an isolated system to produce more energy than is put into it, and with all this energy being lost as heat, less and less energy cycles through the system until eventually the battery is no longer able to power the machine and the machine stops.

    The best way to make your set up more energy efficient is to remove the whole alternator concept unless you plan for the alternator to be driven by some external power source. For instance, you can hook it up to an exercise bicycle and occasionally pedal some to supply more juice to the battery. Or every once in a while you can run some jumper cables to your truck and crank it up and let it run for a few minutes to recharge your isolated system.

    You need an external power source.
     
  7. Deadman_ny

    Deadman_ny Spaceman

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    Foregoing the hampster idea. ;)
    I'm am gong to give this idea a try. If I didn't it would be one of those things that would bother me. I'm hoping if anything to increase the run-time of the inverter off a battery as was my original hope in all of this. I did a simple drawing of the setup I'm looking to create.

    I have a 1/2 HP 120 volt motor. I'll have to see the RPM's and draw but it's dark out... I'm going to the car junk yard in afternoon before they close to look for an alternator; preferably from a full size pickup or larger with a built in voltage regulator. The pully size is what I need help on because if the alternator isn't being spun at high enough RPM's it won't charge properly if at all.
     

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  8. Frosty

    Frosty a full fledged GF

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    This is only going to run your battery down faster than if you didn't do it. Current that isn't used isn't created in the first place, and since the motor and the alternator and all the lines are less than 100% efficient, you're just going to spend a little extra current to run the thing that wouldn't have been spent in the first place, thereby running down the battery at an accelerated rate.

    You're not going to make a perpetual motion machine; you're not even going to slightly extend battery life. No one can escape the basic laws that govern the functioning of the universe. In the system you have drawn, current will only flow if that process increases the total entropy of the system, in other words: if it drains the battery. If the flow of current can not serve that end, then you'll have no electricity, plain and simple.

    The only way to extend the length of operation of your battery by any measure is through the addition of energy from outside, be it you turning a crank, or a solar panel or a little internal combustion motor or whatever, but at that point it's no longer an isolated system as you have diagramed, and it utterly defeats the purpose of the electric motor and alternator.

    Also, this just occurred to me: we're talking about a batter here - that's DC. You wouldn't want an alternator; you'd want a generator.
     
  9. Jetlag

    Jetlag Rear Admiral

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    The alternator is very slow at what you're proposing, connecting a wire from one side of the battery to the other is much faster.
     
  10. Andrewas

    Andrewas Rear Admiral

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    Yeah, thats what I thought you were on about. Trust me, it wont work. Second Law of Thermodynamics.
     
  11. Frosty

    Frosty a full fledged GF

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  12. Max Gene

    Max Gene Spaceman

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    You should try selling that to despair- I laughed.
     
  13. privfan

    privfan Commodore

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    I laughed too, but it should specify what law. as is it the wording seems to mean he didn't go to law school
     
  14. privfan

    privfan Commodore

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    just throw a transformer into the mix ;)
     
  15. Andrewas

    Andrewas Rear Admiral

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    A bridge rectifier is what you want here.
     
  16. Nomad Terror

    Nomad Terror Rear Admiral

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    This doesn't violate the second law of thermodynamics because it doesn't attempt to convert thermal energy into mechanical energy. It violates the first law of thermodynamics because it attempts to have a closed system produce more energy than is already in it.
     
  17. Frosty

    Frosty a full fledged GF

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    Both, actually.
     
  18. Frosty

    Frosty a full fledged GF

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    So, Professor, how did your ground-breaking project work out? Have you revolutionized the way we use electricity? Have you solved all of Earth's energy questions?

    Do tell. I'm sure we're all very excited to hear of your glorious success.
     
  19. Mjr. Whoopass

    Mjr. Whoopass <FONT color=lightblue><B>I was going to say someth

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    "I have not failed, I've just found 10,000 ways that won't work."
    Thomas Edison's response to the idea that he had failed after 10,000 experiments to develop a storage battery, as quoted in The World Book Encyclopedia (1993) Vol. E, p. 78

    Good job on trying something deadman_ny. Even if your experiment didn't work, I'm sure you learned things from it. I had a freshman year High School science project where I had my own failed attempt at perpetual motion. It's one thing to read about the laws of thermodynamics, but actually trying something is the best way to learn and understand it at a deeper experiential level.
     
  20. Frosty

    Frosty a full fledged GF

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    You're such a jackass.
    No, he didn't try anything. Don't complement him on his second-grade perpetual motion machine unless you want everyone to think you're a stupid retard as well.
    It wasn't an experiment; it was fucking around. Furthermore, he shouldn't have had to learn anything from it at all. This is the sort of completely elementary thing that people tell you so you can skip chasing your tail. It's written down in books. No learning should have come from it, because he should have already known the outcome.
    You're pathetic. This is all really simple stuff a person should have figured out before middle school. There is no deeper experiential level. You either understand it or you don't, and the nature of the understanding is very simple: this does not work.
     

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