30 Replies Latest reply on Apr 20, 2017 11:54 PM by ntewinkel

# Battery Charging using DC Motor

I have been trying to wrap this idea around my head that I can successfully charge a battery by using a DC motor.  Here is the example:  You have let's say a 16,000mAh 6S Lipo Battery.  This battery is your primary energy source.  This battery will power a brush-less DC motor.  When the DC motor is creating high RPM's, this energy would be used to recharge the primary battery, while also powering other components within the device.  In this example, the device housing these components would be a cooling fan for a motor design I am working on.

Is this possible?

If it is, one thing I concern myself with, is that the battery designs of today, mostly only have one connection, which is used to plug into the charger or to plug into the device you wish to operate.  If this is in fact possible, I would like to speak further with you on perhaps helping me develop a solution.  Thanks!

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Sounds like those mythical 'free energy' ideas. If the battery is powering the motor, then a certain amount of energy is needed to do this. That energy came from the battery (due to a chemical reaction).

If you wish to use the motor to charge the battery then that energy comes from.. that's right, the battery itself.

So the answer is yes, it is possible (with a complex circuit since you're using a brushless motor) to charge a battery but won't result in anything useful since work is being done to put energy back into the battery (and that energy originally was supplied from the battery) and you have conversion losses at all stages. There are probably hundreds of such discussions on the Internet - for some reason it seems a popular thought. See here for some more discussion on it: https://www.physicsforums.com/threads/how-to-use-an-electric-motor-to-recharge-a-battery.535694/

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The motor would in fact be supplying cooling power, so it will absolutely be useful.  So I guess the better approach on this, is to determine what amps/volts, etc. are coming from the battery to the motor, and how many amp/volts are needed to continually run the motor?  I am not sure on the size of the motor as of yet, but I believe I will need at minimum 35,000 rpm's, which would be equivalent to approximately 6437 grams or 14.19 pounds of thrust, with a 8.5x5 fan blade.  According to research, this would be optimum for the size of the engine block, which is very small!  So this is where I would get stumped.  If the battery draw is let's say 12 volts (I am only guessing), then the motor needs to produce more volts to replenish?  It seems that this is possible from what you say, I think.  As for (complex circuitry), what would I need?  Can you give me a real world example, based off the minimal input that I have thus far?  Don't worry about going over or under on voltage, as I haven't even started on building this cooling fan yet.  I am just trying to get a grasp of one, whether the idea will work, and two, what would I need to make it work.  Thanks for your input.

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Just as I posted my last comment, it seems that I had some others come in.  Lord knows I can't lift myself into the air John.  Okay, so the overall ruling is that this is entirely impossible then.  Got it.  But that doesn't mean I am hanging up the idea.  Let's expand on that.  How about we have two batteries?  One battery supplies power to motor.  Motor provides charge to a second battery.  The second battery is being used to power lights.  Isn't there room for thought on that approach?  Or do I have to pull away from even designing a cooling fan for my motor?  Isn't there some sort of storage bank system to store unused energy?  I am throwing darts blindly.

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Hi Dan,

Example one: We have a battery that is supplying energy to a motor. The motor spins as a result of the conversion of electrical energy into mechanical energy. Heat is also produced in the process and this energy is lost to the environment and is not practically recoverable. Suppose for this example 80 joules of energy is going into spinning the motor and 20 joules of energy is being wasted as heat. This motor is said to be 80% efficient. Now let's assume that we have a crank on the motor and we can turn that crank very fast. We begin turning the crank with all our might and the chemical energy of our muscles is converted to the mechanical spin of the motor. At some point we will be spinning the motor fast enough so that it is no longer using energy from the battery. The crank is keeping the motor spinning and the electricity that is being made by the motor by our efforts on the crank exactly equals the energy supplied from the battery. At this point the system is in electrical equilibrium. If we want to charge the battery however we have to increase the energy and speed of the turning of the crank. Now the voltage that we are producing by turning the crank is greater than the voltage of the battery and energy starts to flow back into the battery and the battery recharges. In this direction we will not be as efficient and perhaps 50% of our effort will be lost to heat and will not be practically recoverable. Since electrical energy can only move one direction at a time we can not use the battery to spin the motor and use the spin of the motor to recharge the battery simultaneously at the same time. We also loose energy to heat in both directions.

Example two: We have a battery spinning a motor and at the same time we have a battery of a lower voltage connected across the circuit. In this case energy from the higher voltage battery spins the motor as before. Energy from the higher voltage battery will also flow to the lower voltage battery and recharge it. However the energy we loose from the big battery will be much greater than what is gained in the smaller battery. All the while we are doing this the motor will run use the same energy as before and contribute nothing.

There are no circuits no matter how sophisticated that can get around the fact that we can not create energy. We can convert energy from one form to another but always with a cost of loss of some of the energy that is converted. It is like pouring water from one container to another using leaky pipes. We will always have less after the process than we began with. Check out the Second Law of Thermodynamics.

I hope this clarifies a bit.

John

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Hello John,

I enjoyed reading your post on thermal dynamics. When I was younger and did not have the training I have now. I too had the dream of making a perpetual motion device too. But since then, and with the advancements in the field of electronics its getting closer to that dream of coming true. Lets break  your explanation of thermodynamics down to its basic form. electrical energy - turns the motor and trans forms to mechanical energy - as a result of friction the mechanical energy produce heat which until now was unrecoverable. which results in energy loss. Just suppose there was a way to recover the heat loss and transform it back into electrical energy. I understand that we will not be able to totally recover all of the heat, but if enough was recovered and turned back into electrical energy. This was an Ideal I had but getting and understanding the same explanation you gave I let it go until I seen on inscrutables an article on how they are converting heat back into electrical energy. here is the link   Recycled Energy - \$7.50 Generator! - ThermoElectric Generator. They use this generator to charge cell phones and tablets with a candle. I also understand that in small scale this Ideal is useless. But what about large scale like hydroelectric generators, or electric pole generators where a lot of heat is expelled?

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Hi Douglas,

Recovering energy from heat generated by the motor in its normal activity is not the same as using a motor to drive a generator, which was the question the original poster asked.

The original poster had a battery supplying power to a motor which was performing some useful purpose (not mentioned - lets say perhaps driving a fan). In addition the original poster wanted to use the motor to also drive a generator to charge the battery back up. This actually would have resulted in less operational time before the battery needed a recharge,because of additional inefficiencies - therefore would have actually been worse than just using the battery to drive the motor to drive the fan in the first place.

Regarding your point, yes if there are inefficiencies resulting in heat then that could be collected to allow the battery to run longer. Another option is to make the motor more efficient, e.g. with better bearings and better commutation. In some cases DC motors can be very efficient (more than 90%) so the motor would at best run for under 10% longer.

For large scale generators I think they may already perform heat recovery. Businesses can also do things to recover this energy. There is a useful website here.

I too had the dream of making a perpetual motion device too. But since then, and with the advancements in the field of electronics its getting closer to that dream of coming true.

It isn't. There are no advancements in the field of electronics that could achieve this.

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your right, I was just was just trying to break down the laws in which John had explained so well. To try to reclaim the heat loss and convert it back into a useable power source. and the only way I know to make a motor more efficient is to get rid of the friction created from the motor turning and the bearing rubbing on the two surfaces. one method would be super cooling or placing the motor in a vacuum. but for DC purposes are not feasible. so without finding a way to reclaim the heat loss or get rid of the friction, no there is no way at present recharge the battery with the motor as it is. I was just thinking outside the box.

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Hi Douglas,

Thinking outside the box is good. shabaz did a good job of summarizing and expanding my post. Certainly some energy can be recovered if there is a need for the energy and if it is economically justifiable. In most cases the cost of the harvesting or recovery technology is more than the value of the return. By the way I think most of the heat loss in a motor comes from resistive and inductive losses rather than friction. 2AM here and time for me to shut down for the night.

John

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Lord  knows I can't lift myself into the air John

Absolute classic! i just burst out laughing for no apparent reason as far as the people round me are concerned hah!

On a serious note... like others have already said, the energy that turns the charging motor must come from somewhere, heres another example; Your car battery keeps its charge because of the alternator motor that spins from the cars engine.

Its easy to believe that this energy is free because the engine is already running but in reality causes a small amount of drag, and wastes some energy through heat, light and sound. This results in the engine consuming more fuel, but its considered a worthwhile system cost to keep the battery topped up.

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This is the second principle of the thermodynamics.

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Hi Enrico,

Sorry I was still typing my post when you mentioned the second law of Thermodynamics so I didn't see that you had already mentioned it until after my post.

John

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Repetita juvant friend ! But this seems having no effect on a lot of free energy inventors

My general question is - how is it possible that someone tried to propose energy solutions, ANY kind of energy solution, without knowing the minimal, essential, laws that roles our part of universe? This is the real mystery ...

Enrico

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how is it possible that someone tried to propose energy solutions

What amazes me more is that it wasn't thought of before ....

Enrico ....Didn't you know you can find all the answers on the internet...they might not be right, but because they are there they must be.

I think the fundamental understanding about energy is that it is always converted into something ...it's never lost just converted.

Because there are no free lunches ... some is always lost ... usually to heat, hence nothing will ever be 100% efficient, there will always be losses.

Mark

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I think that we should make an Arduino project demonstrating the Carnot cycle with sensors it's not difficult to see the disperse entropy and why adiabatics are not straight lines ...

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Hi Enrico,

I have found that people who use their imaginations to try to come up with new ideas, even when they do not have an in depth background in the science, are often the source of new and innovative things. This is because they have not yet been taught what is impossible and they are free to go beyond the bounds of this restriction. I hope that Dan doesn't get discouraged as he asked his question in a very well written way and he did a good job instigating this discussion. If you proceed to use the Arduino to demonstrate the Carnot cycle it will be a very interesting project but you will have to give Dan some of the credit for the inspiration.

John

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in my opinion, you are true and not true (something like a shroedinger reality). Over the top irony should be always welcome, in my opinion.

The idea was not to discourage you (Dan) as I spent months of my life when I was child to understand why what you have asked was not possible. Until someone has not shown me the illumination of the entropy principle. The point is that as far as what I see in a self-teaching path (I trust much in this approach, personally) it is best practice to search and acquire first what are - if any - the scientific rules beside something that is not simple to understand.

I wrote:

My general question is - how is it possible that someone tried to propose energy solutions, ANY kind of energy solution, without knowing the minimal, essential, laws that roles our part of universe?

This does NOT mean "you should know before asking" but "be curious and search to see what is the point". I agree with mcb1

Didn't you know you can find all the answers on the internet...they might not be right, but because they are there they must be.

That is the sense of the question.

Enrico

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Hi Dan,

shabaz is correct. If you make a motor spin with a battery the energy comes from the battery and is converted to mechanical energy and heat in the motor. In order to charge a battery with a motor it is necessary to use mechanical energy to spin the motor and the energy then comes from the source of how you are spinning the motor and goes to the battery where it is converted to chemical potential energy and heat. There is no way to use a battery to spin a motor and use the same motor to charge a battery at the same time. This would be like reaching down and grabbing your own ankles and lifting yourself into the air. There are a lot of snake oil sales people trying to sell these ideas but there is no free lunch when it comes to energy.

John

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I just love the analogy

Peter

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Of course you can charge a battery from a dc motor, that's how generators work.  You just can't do it at the same time you're powering the motor.

Look up regenerative brake "https://en.wikipedia.org/wiki/Regenerative_brake"

Keep thinking,

Scott

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it is possible and i have seen such

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I am quite sure that you have NOT seen any such thing but it may be that some freak circumstances or clever tricks have deceived you.

If you could describe what you have seen and better still offer pictures or links I'm sure that plenty of E14 people will be very happy to explain what you might have seen - and why it doesn't do what it seems.

MK

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I suppose if you had two sets of armature coils you could technically "charge" the battery from one set of coils and discharge the battery from the other set of coils.  Although arguably you couldn't say you were charging the battery because the net flow of current would be out of the battery not into it.  It would be more of a Rube Goldberg experiment than anything else.

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Look up regenerative brake

But the power from regenerative braking comes from slowing down the vehicle. It takes much more energy to get that vehicle moving than you get out of regen braking. Except when going down a hill, but eventually you'll have to get back up that hill.

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I wanted to add one thing to this discuss:

Conservation of Energy.

Once you understand that you will understand everything

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Seems to me, that if you generate 120 volts from say an alternator. Then you can plug in a battery charger and fans and everyone is happy. I'm working on a similar project.

i need to charge my trolling motor battery. I'm trying to create more power than I use . A 12 volt motor makes 120 . This in turn powers2 battery chargers. I got to say , it hasn't happend yet. But I won't give up.

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i have a local self charge power generator. am yet to come up with reasonable scientific explaination. until then do not doubt the imposible cuz it is already there in nature

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Wow, it is very simple and a few good engineers have already tried to explain

There is no free lunch, there is no system that is 100% efficient, never mind over 100%, there are some very lab science research specific examples that are close to 100% but still less than 100%

Due to friction, Heat, Resistance, etc you will NEVER get out what you put in. Conservation of energy is real and a fact.

Do you really believe that if I connect a motor to a battery, the motor will get to the point where it is not drawing power from the battery and in fact can reverse the flow and start charging the battery instead, this would mean that the motor (Lets say it takes 100W to turn it) it is generating over 100W internally + any heat loss, friction loss and resistance loss, then in addition, it is generating enough to also re-charge the battery, this would mean it is generating in excess of perhaps 120W on its own. therefore if you could simply start the motor spinning without a battery (Perhaps a lawn mower starter cord) you could have it power a 20W light bulb and itself forever, now that would sell right. but it is impossible.

This goes right along with Water Seer Wind-powered Water Seer pulls 11 gallons of clean drinking water from thin air | Inhabitat - Green Design, Innovation, A…

and the like. Actually both the roadways and the water seer will actually partially work at least, given just the right circumstances, just won't be returning any investment in the next 10,000 years or so... and are so far from meeting even part of their claims it's not funny

When you get a bunch of really good engineers telling you the same thing, perhaps they have a point?

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Due to friction, Heat, Resistance, etc you will NEVER get out what you put in. Conservation of energy is real and a fact.

Agreed - the only way to get more energy than you put in is to steal it from somewhere else.

For example, heat pumps are considered more than 100% efficient (compared to direct use of electrical energy through a resistor for heat) because they move warmth from outside of the house to inside. But the "free" energy is obtained from the heat in the outside air.

I don't see how the Wind-powered water generator and solar roadways pertain to this free energy question.

I might be reading it wrong, but that wind-powered water maker seems to use wind power to push moist warm air down into an underground reservoir which I presume is cooler and causes the water to condense out. Seems legit. I'd never use it here in my temperate rainforest, but I suspect certain desert areas could benefit. Although like you said, might not be worth the investment, especially if drilling a well (where possible) takes less energy to begin with.

The solar roadways use solar panels to generate electricity. Solar panels are already proven legit. Not sure if it's financially worth it, but I guess part of the claim is that those roadways will last longer than regular tar-based pavement. Might work well in places like California where there's plenty of sun and it's never covered by snow. Maybe using those panels just for cross-walk and other special danger areas could be worth it for the safety factor.

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Water Generator... Claims to generate water 7*24*365.

No Wind, No Water

No Moisture in the air, no water (Desert Regions)

you need to dump heat to get the water to condense, this heat goes into the surrounding soil and heats it up, we're talking kilowatts of power based on the claimed water output !!!!!, warm soil = no condensation

Day and Night... nigh it gets colder, usually colder than the soil, so no condensation

if there is wind and low humidity, all the wind over the water in the container will evaporate it

anyway, its a complete scam, the physics does not add up, same for solar roadways, same for using the motor to charge the battery is is running from.

There similar because there all examples of where people try to demonstrate breaking the laws of thermoDynamics, Conservation of energy and other fundamentally sound engineering facts by quoting all sorts of fancy terms that have no foundation in true research and appear to just be scamming money from gullible folks who dont know better.

In this case the poster is convinced by the apparent output (Greater than unity gain of input to output ) but does not have the background to know it is not possible

Even your example of the geothermal, if you just stick to energy in vs out rather than money in vs product out, it is still not 100% efficient and certainly not greater than 100%. yes you're providing less PAID for energy that you get out, but that other energy is coming from the surrounding ground

anyway, I digress.

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Ah ok I understand, I didn't even think of those details. And yeah I have no idea how soil temperature works in deserts. Here it's generally cooler, but we're relatively quite far North, and I think there's a ground-water factor. The over the top claims especially are where it falls apart (I didn't read those details). Not the first time someone has taken something that's theoretically possible and then added a "marketing spin" to make a buck. It would probably output that amount of water where I live, if you add the rainfall

And right, thermodynamically speaking heatpumps are definitely not that efficient. It's based on financial and applied-energy efficiency for heating only.