DIY: Generator

[tash]

Thanks for being a good sport and the Mrs' also.

Indeed 

[TimSuggs]

Thanks for being a good sport and the Mrs' also.

Indeed 

Ditto on the "good sport" thing (again...).  Something tells me you two (Mr & Mrs Tash) are tighter than two ticks in a bikini! 

Where do I get my lines?  I write for Hallmark!  Well, no...  But I do have a friend who puts on his wife's leotard and rides his bike across Oklahoma on a regular basis that I poke a lot of fun at.  I call him the "Spandex Avenger" and write about his exploits at great length from time to time, so I have a little practice coming up with the storylines.  Sorry about the keyboard and monitor, yours isn't the first if it's any consolation my friend.

OK... Back ON TOPIC!  Now, no electrician am I, but I do know that the slower you can charge a lead/acid battery the better it is for the battery.  I think you could hook a freaking welder to one and "minute charge" it, but I don't think it's gonna last too long.  BUT... In a survival, retreat or off-grid setup where you might be running totally 12vdc and have a bank of batteries, then your idea about equipping the riding mower with a few alternators to take advantage of the HP has some merit.  One of the guys I Jeep with has an on-board welder/alternator, and depending on how large the "retreat" was, having a drivable mini welder has some merits too.  Oh, the ideas...

Tim.

[Dan]

Does anyone know how many RPMs it would take for the alternator to reach 12 volt. 

Wondering about the possibility of mounting one to a stationary bike or something of that nature if gasoline were to run out.

Check out the Alternators at Wind Blue. They have alternators that reach 12 volts at 150, 275, 475, and 1200 rpm to choose from. Figure out what the gearing would and what kind of pace you want to maintain and choose accordingly.

[DIM TIM]

Does anyone know how many RPMs it would take for the alternator to reach 12 volt. 

Wondering about the possibility of mounting one to a stationary bike or something of that nature if gasoline were to run out.

Check out the Alternators at Wind Blue. They have alternators that reach 12 volts at 150, 275, 475, and 1200 rpm to choose from. Figure out what the gearing would and what kind of pace you want to maintain and choose accordingly.

  Thanks for taking the thread back from the hijackers Dan. Good post. You would get a +1 from me for sure. I have the site from Texas Squirrel's post in my favorites file from a year ago. Hope to get things together to try one out this Spring, or maybe Summer. It would be nice to be able to match the unit to the needed application.

[Da Fat Kid]

Good job Tex. While you are putting fender washers on the engine you may want to put one on the adjustable side of the alt if you haven't.
WCFF  you have a good idea using the lovejoy BUT keep in mind that you may run into a direction of rotation problem and with the LJ you have no way to adjust speed. the best speed for the engine may not be the right speed for the alt.

[Da Fat Kid]

OMG  me little pea brain is kickin now! For those who may live where there is more wind. Here is another option and TOTALLY FREE to operate. Cheap car waterpump or better yet divorced fan drive connected to alternator mounted up on pole with a swivel so it can rotate into the wind. Run the power cable down the center of the pole so there is no worry about wrap up. The larger fan the better. Just like the "old school" wind mills.

[backwoods_engineer]

Thanks for the great pictures and writeup, TexSquirrel.   I just ordered a plate, pulley, and belt from Epicenter.

I have a 3-HP vertical-shaft engine from a previous kids' go-kart project (even has a cast-iron flywheel for easy starting).  I have an alternator already, but may buy a new one from AutoZone, considering they are so cheap.  I plan on putting it all together when it comes in, mounting it in my attic where the water heater is, and eventually running the motor off natural gas.

I already have a solar-charged battery bank that runs my ham radios and the lights on my bench, but I want to expand that to a generator-backed battery bank that powers 12V LED lighting throughout the house that automatically comes on when the power goes down.  This generator I'm building will be for recharging and running that bank and lighting.

I will post pix when stuff starts to come in.

[pokeshell]

I am going to try this for my camper. Between solar  this, and making your own alcohol fuel, I could basically get free power. Any good place to find or make mufflers for lawn mowers for cheap? I would like to get the mower a quite as possible.

[onesojourner]

I have a brand new 6 hp tiller motor. How many hp does it take to run a alternator? I think in the first season of the colony they ran 2 off one motor fueled by a gasifier. That would be about 1-2 hp per alternator.

[GreyWolf]

IDEA! Big wheel on lawn mower, little wheel on alternator which is  hooked up to battery which is hooked up to inverter. 110 from 12 volt. Big wheel turns once and little wheel turns four times.

[machinisttx]

I know this is an old thread, but I ran across it and I've done a fair bit of research on this in preparation to do it myself. Might save someone some time and internet searching.

1. From everything I can find, it typically takes around 1hp for every 25 amps of alternator output.

2. Alternators typically need to spin around 8000 rpm to achieve max output(amps). You will need a pulley on the engine(assuming it's a 3600rpm gasoline engine) about 2.5 times larger than the one on the alternator to achieve this.

3. Other than the epicenter, you will not find a pulley for the alternator that will allow you to run standard industrial v belts instead of automotive V belts. Automotive V belts and industrial V belts are quite different and not interchangeable. Automotive belts won't fit properly on a sheave designed for industrial belts and vice versa. Machinery's Handbook has dimensions for the pulleys and belts, newer editions include dimensions for K section poly-v belts(automotive serpentine belts). I'm a machinist by trade and will be making my own poly v pulleys for the engines.

4. You can use just about any alternator for this project. Internally regulated designs like the 10 and 12SI are easier to wire up and don't require buying anything else to make this work. The 10 and 12SI are also as common as dirt and pretty cheap. Check automotive salvage yards for late 60's through mid 80's GM cars/trucks. Externally regulated alternators will need a little more wiring and an external regulator, but will work just as well.

5. The alternator doesn't care which way you spin it, but the internal/external fans do. It will make power no matter which direction it turns, but it's best to spin it the correct direction for proper cooling. Alternators will generate a significant amount of heat when they are outputting a lot of current. If the cooling is not sufficient, then the rectifier diodes will burn out...no more power output. It only takes a few minutes to replace the rectifier assembly, but why burn it up needlessly?

6. It may be beneficial to add a rheostat into the circuit that sends power to the slip rings. By doing this you have a manual override and can slow down the charge rate, or you can turn it all the way up to get max output. This also allows you to reduce the load on the engine if necessary.

7. Alternators are rated "cold" and at max output. Typical output will be below the rated number.

[Carl]

Just some thoughts on this is most auto alternators need 2000 RPM SHAFT speed to give full output
though you can get some power at lower RPM and most single cylinder engines need a pulley to allow
the engine to run at some speed to have enough horsepower to keep speed up under the load
(you need about 1 horsepower per 500 watts output) so even a 3 Horse engine will do OK with typical alternators.

Don't expect over 75% of alternator output for any length of time as HEAT will drop efficiency quickly.

Some vertical shaft single cylinder engines need a bit of weight on the shaft (heavy pulley) to hold down vibration while running
or they will have lower expected life due to stress .

[Fixit]

Typical turn on is 800 rpms . Max rpm output depends on the alternate r. The higher the max output the poor the output at low rpms . Personally I like a 100 / 130 amp alternater . That said I did set one guy up a duel 200 amp alternater system useing a 1 cyl. Diesel motor that wad 14hp . Here's what I have learned from 20 years of doing these .
1. Oversize your motor.
2. Oversize the pulley on the motor .
3 . Go with the smallest pulley you can get on the alternator .
 Now here's why. While you can go with a motor just big enough to do the job you will have to run it wide open and that makes for a short life on the motor. If you go with a bigger motor and a bigger pulls on that motor you can run it slower while still spinning the alternater fast enough . My curent setup uses  a 8hp Briggs and a 100 amp cs130 alternator with a SE ( 1 wire ) regulater in it . The motor runs just barley over an idle to put out the charge I need..  With out going to measure I think the motor pulley is 7" and the alternater pulley is 1.5" .
 There are a lot of alternaters that you can get 1 wire regulators for now .but the old 10si/12si is still the easiest to work on for the layman. Those 2 200 amp alternators I did for that 1 guy were L/N s.
As a footnote I am a alternater/ starter rebuilder so if. You can't find what you need give me a shout but most of the time the parts you will need are on ebay and by the time I would ship it to you that's probably cheaper.

[machinisttx]

Just some thoughts on this is most auto alternators need 2000 RPM SHAFT speed to give full output
though you can get some power at lower RPM and most single cylinder engines need a pulley to allow
the engine to run at some speed to have enough horsepower to keep speed up under the load
(you need about 1 horsepower per 500 watts output) so even a 3 Horse engine will do OK with typical alternators.

Don't expect over 75% of alternator output for any length of time as HEAT will drop efficiency quickly.

Some vertical shaft single cylinder engines need a bit of weight on the shaft (heavy pulley) to hold down vibration while running
or they will have lower expected life due to stress .

Where are you finding info that says an alternator gives full output at 2000 rpm? Late model alternator or older design like the 12SI?

Here's a graph for an ACDelco 12 SI. 5,000 rpm for max output.



Here's one for a much newer CS144. Still going up at 7,000 rpm.


1 mechanical horsepower is equal to 746 watts. It's not as simple as that though. The engine must be oversize for the application to allow for surge loading and various inefficiencies(belt drives and cooling fans, for example).

The verticals that need extra weight are the newer style with aluminum flywheels. The old style with cast iron flywheels don't need it, but it won't hurt them. Adding a big, heavy pulley will allow you to slow the rpm down as well.


Fixit, can you explain how to run alternators in parallel? If I understand correctly, it only requires a jumper(from alternator to alternator) between whatever energizes the slip rings. I completely forgot to ask my local alternator guy the last time I was there.

[Fixit]

My memory said that there is nothing special on duel alternator systems.

https://www.youtube.com/watch?v=AZ7_HYtWS0Q

How many do you want to hookup? The one duel  I did on that diesel motor was going to 2 different battery banks he then had the inverter on a solector  switch to chose battery banks.  You see dual and triple alternators in lemos, ambulance, buses and the like .
 As far as the rpm charts look at that power curve when you get over 2000 rpm on the 12si and 3000 rpm on the cs144 . All you are really doing is wasting fuel once you past those points. Factor in that an alternator is most effectively converting power when it is working at 50 to 60% of its rated output. A lot of the newer stuff have a thermal sense in the regulator to cut them off if they get very hot.
 On your motors my small engine guy said that if you look for a motor for a pressure washer that they have a heavier flywheel that a lawnmower motor.

[Carl]

Just some thoughts on this is most auto alternators need 2000 RPM SHAFT speed to give full output
though you can get some power at lower RPM and most single cylinder engines need a pulley to allow
the engine to run at some speed to have enough horsepower to keep speed up under the load
(you need about 1 horsepower per 500 watts output) so even a 3 Horse engine will do OK with typical alternators.

Don't expect over 75% of alternator output for any length of time as HEAT will drop efficiency quickly.

Some vertical shaft single cylinder engines need a bit of weight on the shaft (heavy pulley) to hold down vibration while running
or they will have lower expected life due to stress .

 

This is correct,little on this world is made to give 100% of what it is advertised to do.My focus was on having a efficient,long working project.

[machinisttx]

My memory said that there is nothing special on duel alternator systems.

https://www.youtube.com/watch?v=AZ7_HYtWS0Q

How many do you want to hookup? The one duel  I did on that diesel motor was going to 2 different battery banks he then had the inverter on a solector  switch to chose battery banks.  You see dual and triple alternators in lemos, ambulance, buses and the like .
 As far as the rpm charts look at that power curve when you get over 2000 rpm on the 12si and 3000 rpm on the cs144 . All you are really doing is wasting fuel once you past those points. Factor in that an alternator is most effectively converting power when it is working at 50 to 60% of its rated output. A lot of the newer stuff have a thermal sense in the regulator to cut them off if they get very hot.
 On your motors my small engine guy said that if you look for a motor for a pressure washer that they have a heavier flywheel that a lawnmower motor.

I don't need to run more than two, but they will be charging the same battery bank. I know some of the late model GM and ford SUV's with front and rear AC have dual alt setups from the factory, but I've never seen one in person so I have no idea how they are wired. I am under the impression that if they are not configured in a specific manner that one would cause the other to "turn off". A battle of voltage regulators I suppose. I want both alternators producing power. I know Leece Neville has a particular series of alternators that are designed to load share. Four of them can be paralleled to get around 1200 amps of output. The regulators on that series of alternator has a specific terminal that allows them to "communicate". http://www.prestolite.com/literature/alts/PG1011_Multi-Power_System.pdf

Efficiency goes down over XXXX rpm, yes, but since we're getting rpm via the pulley ratio, the engine rpm could be at idle speed, wide open throttle, or anything in between to achieve that. I'll have to check out the pressure washer engines...I see tons of them at the scrapyards.

Carl, I'm not sure why but I misread your previous post(500 watts per hp). The extra weight is needed on the motors because the factory engineers them to utilize the blade and blade mount as part of the crankshaft balance.

Here's something kind of neat. Takes adding heavy pulleys(not really pulleys in this case though) to the extreme. http://youtu.be/zhmZOuK5V4Y