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Homemade Wind Generator Advice

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*Peter *

New Member
Hey guys...
The object of this project is to design and produce a wind generator prototype which can be portability charge batteries (12V) and or other appliances such as a phone. The components I will be using is a DC motor, which has been taken out of a portable fan. This motor has been tested to produce about 3.2V at a decent rpm.
I was thinking, is there any way that this motor can be aligned with other components to charge appliances and batteries as stated above. If this scenario is practical, what other components are needed (If required) and can this setup be sufficient to charge a 12V battery.

Feel free to expand on other ideas on how to make a functional Homemade Wind Generator.
(Note; I am pretty new to this so keep in mind) :)
13340793_1556728971295462_160163672_o.jpg 13340935_1556729007962125_718739826_o.jpg

Thanks in advanced
 

alec_t

Well-Known Member
Most Helpful Member
This motor has been tested to produce about 3.2V at a decent rpm.
Welcome to ETO!
A charger must provide a higher voltage than the battery it charges. What current can the motor provide at 3.2V? Unless it's high enough to get a 'decent' output current from a DC-DC boost converter then it won't be suitable for battery charging (other than for single cells of < 3.2V rating). I suspect you are going to need a much bigger motor/generator to be practical.
 

spec

Well-Known Member
Most Helpful Member
You could consider a Dynohub from a bicycle.

Pretty much any voltage can be converted to any other voltage suitable for battery charging (14V) or powering a USB (5V) for example. But as Alec has said, it is a matter of power. Power is calculated by multiplying the volts and amps. It is no use having one without the other.

Take an example of powering a USB interface. Say the USB interface is 5V at 1A, the power required is 5V * 1A = 5W. So your fan motor would need to produce, 5W/3.2V= 1.56A.

You can test your fan motor output current by placing a 2 Ohm resistor across the fan motor output and measuring the voltage. If you do that and let us know what the voltage is we will then have an idea of the performance of the fan motor when used as a generator. If the voltage is still around 3.2V, put a 1 Ohm resistor across the fan motor terminals and take another reading.

Can you tell us about the 12V battery that you wish to charge: what type, what capacity?

spec
 
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Grossel

Well-Known Member
I would strongly suggest to use something else than a regular DC motor. My experience is that the generated output voltage is far lower than the rated voltage for normal use. Those old bicycle generators that I have tried to use needed some momentum before they would let spin around, so that could be a problem if the physical size of the fan is small. But it's better then using a DC motor.
 

spec

Well-Known Member
Most Helpful Member
I would strongly suggest to use something else than a regular DC motor. My experience is that the generated output voltage is far lower than the rated voltage for normal use. Those old bicycle generators that I have tried to use needed some momentum before they would let spin around, so that could be a problem if the physical size of the fan is small. But it's better then using a DC motor.
Hy Grossel,

Agree that some DC motors used as dynamos are poor as generators, but you can make a quite good alternator out of a computer fan motor by ripping out the commutation electronics and fitting Schottky rectifier diodes to produce DC.

Are you referring to the bicycle bottle dynamo or the hub type? Both are still used. The hub types would be more suitable for a wind turbine because they are multiple pole and designed for slow speed. (bicycle wheel rotation). In fact all you need to do is remove the spokes and fit fan blades in place. The hub bearing can be used as is, although it would be best to strip the bearing and inspect the races and ball bearings for pits etc. If required renew them. Then re-grease with a high-spec lithium molly grease and adjust the bearings for a free rotation with minimum end float.

spec
 
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MaxHeadRoom78

Well-Known Member
The problem with a P.M. type of generator is voltage control or regulation, I think I would be tempted to use a auto alternator and regulate the wound field and initially connect the field directly across the output until it pulls itself up using a simple relay sensing circuit.
I have done it with high voltage generators and used the residual magnetism in the rotor to start the generation if it is not desired to power the field externally.
An alternator produces a voltage at a very low rpm.
Max.
 

spec

Well-Known Member
Most Helpful Member
The problem with a P.M. type of generator is voltage control or regulation, I think I would be tempted to use a auto alternator and regulate the wound field and initially connect the field directly across the output until it pulls itself up using a simple relay sensing circuit.
I have done it with high voltage generators and used the residual magnetism in the rotor to start the generation if it is not desired to power the field externally.
An alternator produces a voltage at a very low rpm.
Max.
Yeah, that is always the problem, but with electronics you can tame the voltage from a permanent magnet alternator.

An automobile alternator would be a bit big and heavy so the inertia would be too great unless the OP was prepared to make a large assembly, in which case an automobile alternator would be ideal. Potentially you could get 15V at 80A.

Some motorbikes- Honda especially- have a coil rather than permanent magnet for the rotor. Motor bike alternators are a lot smaller and lighter but then you would have to make a bearing to replace the crank bearing.

spec
 
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tcmtech

Banned
Most Helpful Member
DC motors work just fine as generators provided you size them properly. :rolleyes:

If this is to be a small (few watts to ten or so watts) system for charging 12-volt batteries I would recommend finding a 24 VDC low RPM motor like that used in older office copier machines or such. They are low RPM and darn near indestructible and if you ask nice at a commercial office machine repair place you can probably get a few for near free. :cool:

Everything else after that is a matter of sizing your blade set to the combination of the needed motor speed and realistically available wind speed you have to the power output you need which, to be honest, in almost every thread I see about DIY wind power that concept of matching blade size, speed, and motor characteristics to wanted power output seems to be an near impossible thing to grasp. :facepalm:
 

spec

Well-Known Member
Most Helpful Member
DC motors work just fine as generators provided you size them properly. :rolleyes:
Yes, we have had this discussion a few times now. While some standard motors may make good generators, they are not optimum.

Everything else after that is a matter of sizing your blade set to the combination of the needed motor speed and realistically available wind speed you have to the power output you need which, to be honest, in almost every thread I see about DIY wind power that concept of matching blade size, speed, and motor characteristics to wanted power output seems to be an near impossible thing to grasp. :facepalm:
Exactly:)

spec

PS Links

http://cleangreenenergyzone.com/wind-turbine-permanent-magnet-dc-motors/
 
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*Peter *

New Member
You could consider a Dynohub from a bicycle.

Pretty much any voltage can be converted to any other voltage suitable for battery charging (14V) or powering a USB (5V) for example. But as Alec has said, it is a matter of power. Power is calculated by multiplying the volts and amps. It is no use having one without the other.

Take an example of powering a USB interface. Say the USB interface is 5V at 1A, the power required is 5V * 1A = 5W. So your fan motor would need to produce, 5W/3.2V= 1.56A.

You can test your fan motor output current by placing a 2 Ohm resistor across the fan motor output and measuring the voltage. I you do that and let us know what the voltage is we will then have an idea of the performance of the fan motor when used as a generator. If the voltage is still around 3.2V, put a 1 Ohm resistor across the fan motor terminals and take another reading.

Can you tell us about the 12V battery that you wish to charge: what type, what capacity?

spec
The lowest resistor I have is a 220 Ohm, which produce around 2.6V. If i'm correct the output current would be therefore minimal, resulting in a small wattage output... (2.6^2/220) P=V^2/R?

Would I be able to gain a reference (Link) of one of those bicycle generators.

Concerning the 12 V battery, it is a lead acid battery from a car (I think, though it says it's a 'calcium battery' on the battery itself. Not sure what you mean by capacity. All it says is 38Ah?
 

tcmtech

Banned
Most Helpful Member
Well going by a rough estimate if your motor puts out ~3.2 volts open circuit and ~2.6 volts with a 220-ohm load and your battery is a 12-volt 38 Ah....

That gives you roughly 2.6 x .012 = .03 watts to work with which if given a 90% efficiency on stepping it up to the needed 13.8 volt minimum to get a fair charge into the battery, assuming 50% charging efficiency, it would take you around....
(13.8 x 38 x 2)/(.03 x .9) = ~39,000 hours (4.4 years) to charge it up. :sorry:

Or as is you can run a single high brightness LED at about half power. :(

It's doing the basic calculations like this for sizing your generator to the load you need to power and then sizing everything above that to work together correctly comes in. :oops:
 

*Peter *

New Member
Thanks for you responses, also one more question..
I have an alternator from a car but I am having trouble with measuring the voltage output and getting my head around how it should be set up. Could someone show a diagram or explain what wires go where to use this alternater as a charging appliance.
Cheers :)
 

Mikebits

Well-Known Member

spec

Well-Known Member
Most Helpful Member
Would I be able to gain a reference (Link) of one of those bicycle generators.
Your best bet would be to get a dynohub from a scrap bicycle front wheel. In the populous areas of the UK many bicycles are chucked out. But I will get a link for you for a new Dynohub. You would need a bridge rectifier to get DC and would only get around 5W as a guess. On reflection, I now think that a bicycle bottle dynamo will also work and have the same kind of power.

Concerning the 12 V battery, it is a lead acid battery from a car (I think, though it says it's a 'calcium battery' on the battery itself. Not sure what you mean by capacity. All it says is 38Ah?
That sounds like a normal car battery. Calcium is added to many lead acid batteries theses days to increase the strength of the plates, but it does not alter the basic characteristics of the battery.

Batteries are specified by chemistry: lead acid, nickel cadmium (NiCad), Nickel Metal Hydride (NMH), Lithium Ion (LiIon). Then their voltage: Lead Acid= 2.1V (6 cells in series in a car battery=12.6V), NiCad= 1.2V, NMH=1.2V, LiIon=3.6V. (lead acid information corrected 2016_06_07)

Batteries are also rated by their current capacity which is the number of amps they will produce for one hour. Your battery, when fully charged, will produce 38 amps for 1 hour or 3.8A for 10 hours or 380 mA for a 100 hours. Unlike the other batteries though, you can normally only use around two thirds of the capacity of a lead acid battery.

The charging efficiency of a lead acid battery is also low at around 50%, which means, in the case of your battery, to charge it fully you would need to put in 76 Ahs, ie 72A for 1 hour, or 7.2A for 10hrs etc.

spec
 
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*Peter *

New Member
I also have accsees to a treadmill motor. When tested using a multimeter and a speed of a hand push, it produce about 17V at 2.2A... Though it increase to about 50V when someone walked on it. Would this be good for a wind genertor and how can this be applied on making one. Would any one have any schematics on how to make a safe generator using this motor or steps which can be followed. I know the basics on how they work but I don't know enough to make one which can be regulated and contorl in a safe manner.
 

spec

Well-Known Member
Most Helpful Member
I also have accsees to a treadmill motor. When tested using a multimeter and a speed of a hand push, it produce about 17V at 2.2A... Though it increase to about 50V when someone walked on it. Would this be good for a wind genertor and how can this be applied on making one. Would any one have any schematics on how to make a safe generator using this motor or steps which can be followed. I know the basics on how they work but I don't know enough to make one which can be regulated and contorl in a safe manner.
In the link of post #10 which gives an overview of wind generators, they say that a treadmill motor is one of the best.

spec
 

spec

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Most Helpful Member
Car alternators are typically geared up 2:1, so when the engine is turning at 5,000RPM the alternator is turning at 10,000 RPM. This is one of the big advantage of an alternator: you can spin it faster than a dynamo and thus get more power from them when the engine is ticking over at around 1,000 RPM. The other advantage with an alternator is that it has no commutator so the conversion efficiency is better.

The principle of an automobile alternator is that it has a rotating coil and fixed coils (field), typically six (I think).

The connection to the rotor coil is by two slip rings and two carbon brushes.

The out put from the field coils is AC so this is rectified by diodes to produce DC suitable for the automobile electronics and to charge the battery.

The rotor coil is fed with a current from a voltage regulator which maintains the field coil output to around 14V which is suitable for charging a lead acid battery.

Most alternators have the field rectifiers built into the alternator body and most modern alternators also have the regulator built into the body but some are external.

The point to note is that you will get no output from an automobile alternator if there is no current flowing through the rotor coil.

It is not clear from your alternator pictures what the arrangement is with the regulator: internal or external.

Alternators normally have a wire which connects to the ignition light on the car dash.

The body of the alternator is usually the 0V connection and a large connector or wire is normally the positive output.

spec
 
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