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Old 01-14-2010, 04:18 PM
my375hp302 my375hp302 is offline
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Has anyone rigged one of these up? I was thinking that the best power source post shtf is probably 12v car batteries. You can do almost anthing with them, power 12vdc stuff ofcourse, use an inverter to power 110vac stuff, hook three together in series and stick weld 1/2" plate ect ect... But they will need to be charged. Your average alternator puts out 60-100 amps at 14.4vdc in it's operating RPM and is capable of charging two or three batteries at a time. It would be really easy to weld up a mounting system with two pullies and a belt (little pully on the alternator, BIG pully with a hand crank). While it wouldn't be fun to use, it would be quiet and efficent, and should last for years. Has anyone done anything like that?
Old 01-14-2010, 04:27 PM
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I didn't create a hand cranked one, but back in high school I was on the power drive team and I got tasked with making a portable battery charger for our cars batteries. I went to the small engines class teacher and he got us a horizontal shaft engine, then I went to the auto shop and stole an alternator. I used some 3/4 square tube and welded a rectangular base frame with some cross members and quarter inch plates to mount the engine and alternator, then stole a belt from the auto shop to hook them together, and finally welded on some handles to carry the thing. As far as I know they are still using it these days 7 years later. Wouldn't be great because it relies on fuel to power the engine, but it worked wonders.
Old 01-14-2010, 04:31 PM
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hand cranked charger would take a really long time to charge a car battery.you are much better off making a wind powered charger
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Old 01-14-2010, 05:20 PM
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Quote:
Originally Posted by vegasrandall View Post
hand cranked charger would take a really long time to charge a car battery.you are much better off making a wind powered charger
I would think given the same power source (alternator) a wind powered one would take a same amount of time to charge a battery, it would just be easier because you don't have to do anything.

That said, a wind powered one would also be a LOT bigger and would lose it's portability, and is dependant on the wind. What if you need power when there is no wind? A windmill is also easily spotted and could draw unwanted attention. It would also be a lot more difficult to fabricate for the average person.

In a post SHTF situation cars will be everywhere because most of them will be out of gas. Batteries, alternators, and pullies should be easy to come by.
Old 01-14-2010, 05:37 PM
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Heres one for ya I have been trying to figure out for a Amish friend of mine how to charge batteries with low tech so it would not violate there beliefs.So I have been considering this idea ,right now I am gathering parts and am going to see what I can come up with using a HD alternator and an exercise bike .Anyone tried that direction ??
Old 01-14-2010, 05:45 PM
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Quote:
Originally Posted by SurvivalDog56 View Post
Heres one for ya I have been trying to figure out for a Amish friend of mine how to charge batteries with low tech so it would not violate there beliefs.So I have been considering this idea ,right now I am gathering parts and am going to see what I can come up with using a HD alternator and an exercise bike .Anyone tried that direction ??
it works.. you need to make the pully on the alternator bigger and put 1 smaller one on the bike..

A car spins the alternator by a belt now you look at the rpm gage.. higher the rpm faster the alternator spins.. its all conected.. by belts..

so car idles at 1,200 rpm (Revelations per minute) and puts out around 13.2V on a good alternator.. when you crank up the revs the power it can produce goes up as well.. to 14.2 at around 3,000 rpm you need about 13 to charge a battrey min.. you can get away with a little less but its about 13 to charge... you need 12.2V to start an average vechial full charge not running you should see around 12.2v-12.4v
Old 01-14-2010, 07:00 PM
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rigged mine to a 10spd bike.
The rpm you need is around 1200, hard ta hand crank that w out a lot of gearing.
Old 01-14-2010, 07:36 PM
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The biggest problem with any manually powered alternator is the amount of horsepower required to put out usable power.

1hp = 746 watts and the average human can only sustain about .1 to .2 hp.
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Old 01-14-2010, 08:16 PM
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Well, I'll just have to fab one up and try it. I think I have all the crap lying around to do it. I think the drive pully will have to be fairly large to get ehough RPM to the alternator but the larger the drive pully, the more leverage I have to turn it so "in theory" it should be doable. If it works out to something useable I'll take a bunch of pics and post them up for everyone.
Old 01-14-2010, 08:37 PM
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Quote:
Originally Posted by mongoose View Post
rigged mine to a 10spd bike.
The rpm you need is around 1200, hard ta hand crank that w out a lot of gearing.
you use big pully small pully you match it right it will work with out gearing up and down with a slower speed
Old 01-15-2010, 09:20 AM
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Kind of off topic but still relevant...How does a car alternator differ from a dynamo (like in those little hand crank radios)? As far as I know, a dynamo is basically an electric motor, except you turn it and electricity comes out instead of the other way around. But when you describe it that way it really isn't any different from an alternator, so are they the same thing but go by different names?
Old 01-15-2010, 09:42 AM
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Read up

http://www.animations.physics.unsw.e...ricmotors.html

Water is also a very good choice for alternators as a power source. You can create a dam with a chute and then gear it up. The one thing better about this is that you can be far more covert than with wind or even solar.
Old 01-15-2010, 11:11 AM
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I've got a 120 amp alternator mounted to a 6hp Briggs and Straton engine, with about a 3:1 pulley ratio so that I can idle it down for efficientcy under a light load. Under a full load, full throttle, such as a totally dead battery, it will stall that engine. I doubt that a human would do any better, especially considering the gear ratio you would need to spin the alt fast enough to charge. Your going to have to get it up to 1000-1500 RPM to get it to charge. If anything, I would look for a lower output alt from the late 60s that only makes 40 or 50 amps, then try to mount it to a stationary bike somehow. I think you will still be surprised by the resistance. Give it a try, you might be able to make something work.
Old 01-15-2010, 02:12 PM
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With the right gearing/leverage you can make anything work.

The issue being that it may take a lot of work and you will need a way to store the power or use it while it is there.
Old 01-16-2010, 12:45 PM
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Quote:
Originally Posted by vegasrandall View Post
hand cranked charger would take a really long time to charge a car battery.you are much better off making a wind powered charger
Definately. I read somewhere that our arms generally are capable of about 1/4 horsepower. I don't know if that was peak or sustainable output. That ain't gonna generate a lot of power. Legs would be the wiser choice, but if I remember right, they're only capable of about 1/2 horsepower, again not sure if that's peak or sustainable. Considering the worry about lack of calories in a survival diet, I'm not sure I'd want to be expending them to generate a small amount of electricity.

Wind or solar makes more sense to me. It lets you generate power while you're able to do other things at the same time.
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