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Old 11-26-2008, 02:03 PM   #1 (permalink)
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Yes another alternator post

I think I want to try and build an alternator. My idea is to build a permanent magnet alternator only instead of using a belt and pulley to drive it, mount the magnets to the harmonic balancer and put the coils into a block mounted bracket around the balancer. This would also allow you to run an electric water pump and no pile of batteries in the trunk.

The problem, I have no idea how many magnets or how many turns on the coils I would need in order to achieve what Iím trying to accomplish

Anybody know of any resources or have any ideas?

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Old 11-26-2008, 07:12 PM   #2 (permalink)
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Why would having something like that be better than the alternator that is already on the car? You're still going to have drag on the crankshaft. And you're going to have to do a bunch of fabricating and wiring, and put together a circuit with a voltage regulator. AND assuming something like that could work as well to charge to your battery as the factory-supplied alternator, that type of set-up would have little protection from water, mud, grease etc. collecting on its vital parts.

But any, there is a website that I know of (otherpower.com)
that has a bunch of info about home-made wind turbines (giant alternators) that may have useful info for you.
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Old 11-26-2008, 07:33 PM   #3 (permalink)
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Quote:
Originally Posted by Peter B View Post
Why would having something like that be better than the alternator that is already on the car? You're still going to have drag on the crankshaft. And you're going to have to do a bunch of fabricating and wiring, and put together a circuit with a voltage regulator. AND assuming something like that could work as well to charge to your battery as the factory-supplied alternator, that type of set-up would have little protection from water, mud, grease etc. collecting on its vital parts.

But any, there is a website that I know of (otherpower.com)
that has a bunch of info about home-made wind turbines (giant alternators) that may have useful info for you.
i've been watching otherpower for years and its actually one of the only reasons i would even attempt to maybe try building my own alternator. the only problem is it doesnt give may details about the whys of their designs

There are actually a few reasons I think my design would be superior.

1. One of the main reasons that taking the alternator off of the engine gives such a boost is because you are getting rid of the belt and pulley load that is there even when the alternator isnít charging.

2. an automotive alternator doesnít have any magnets of its own it has to generate its own magnetic field which might draw 20 or 30 amps just for that, creating additional load.

3. adding batteries to the trunk adds way to much weight and kills range.

Those reasons on top of being able to run an electric water pump (another belt driven accessory off of the engine) seem like it could give a fairly significant boost.
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Old 12-02-2008, 03:09 PM   #4 (permalink)
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Hey merccom,

I know you want to go the home made alternator route but I would like to lend you some of my experiences running without alternator. I got about a 10% MPG boost when I did it.

I did a lot of research into this as I was experimenting and the deep cycle route is the cheapest and simplest. The weight gain from the batteries does not negate the benefits of getting rid of the alternator. On short trips you can easily run one battery and have a second for longer runs. Mine is set up with a series of Anderson connectors so it takes seconds to load. Think of it this way: Does adding one passenger cut 10% off your MPG? That's the eqivalent of at least two series 27 batts. Just improving the efficiency of the alt (if possible) would be a tiny fraction of the X route.

Quote:
Improving the electrical system's efficiency so it lops 100 W off the average electrical load has the same effect on fuel economy as reducing the car's weight by 110 lbs, as measured by the FTP (Federal Test Procedure) 75 standard profile of starts, runs, and stops
Quote:
A 200-W electrical load accounts for about 1 MPG in the FTP 75 cycle test
IEEE Spectrum: Automotive Electrical Systems Circa 2005

Just sayin' if you are going to go through all that trouble, it should be for the right reasons.

p.s. I love that otherpower site too. Wish I had time to make one of those generators and a windy spot to put it in.
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Old 12-02-2008, 04:02 PM   #5 (permalink)
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Quote:
Originally Posted by orange4boy View Post
Hey merccom,

I know you want to go the home made alternator route but I would like to lend you some of my experiences running without alternator. I got about a 10% MPG boost when I did it.

I did a lot of research into this as I was experimenting and the deep cycle route is the cheapest and simplest. The weight gain from the batteries does not negate the benefits of getting rid of the alternator. On short trips you can easily run one battery and have a second for longer runs. Mine is set up with a series of Anderson connectors so it takes seconds to load. Think of it this way: Does adding one passenger cut 10% off your MPG? That's the eqivalent of at least two series 27 batts. Just improving the efficiency of the alt (if possible) would be a tiny fraction of the X route.




IEEE Spectrum: Automotive Electrical Systems Circa 2005

Just sayin' if you are going to go through all that trouble, it should be for the right reasons.

p.s. I love that otherpower site too. Wish I had time to make one of those generators and a windy spot to put it in.
the main reason i dont want go without an alternator is because i drive for a living.

i'll run between 100 - 150 miles a day. alot of it at night.
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Old 12-02-2008, 05:41 PM   #6 (permalink)
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With alternator delete the real issue is hours of driving. If you are going 60mph most of the time then 2 deep cycles will probably be plenty. I actually keep a spare in the stock position for unforseen problems. Or you could install an alternator kill switch and you will have a safety net.

Vancouver to Seattle on two crappy revived series 27: 123 miles, 70 mph, on arrival 60% discharged, 26mpg. EPA: 20 Border wait: 45 minutes.
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Old 01-20-2009, 08:41 PM   #7 (permalink)
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if your normal battery fails and you have to buy a new one anyway... you may as well get a big 110ah leisure battery to replace it. with UK gas prices the price of fuel vs battery replacement is pretty close but then consider alternator inefficiency and the battery starts to look attractive.
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Old 01-20-2009, 11:18 PM   #8 (permalink)
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If you want to look into something like this, the best info I can offer is MOTORCYCLE engines. They don't use a permanent magnet, that I'm aware of, but they do have an internal alternator with no belt drive.
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Old 01-21-2009, 01:29 AM   #9 (permalink)
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motorcycles and cars vary quite a bit in electrical loads, with a motorcycle you normally don't have a big radio or dual head lights or heater fan, and if you do on a motor cycle then they tend to have a car style alternator that can vary the output, they can also turn the field winding off once the battery is charged, or while you are doing something like starting the engine, the design that is used on cars also tends to operate under a wider range of speeds, allowing it to charge the battery at an idle and not over charge it while going down the highway.

Last edited by Ryland; 01-21-2009 at 01:34 AM..
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Old 01-21-2009, 03:37 AM   #10 (permalink)
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Ryland - obviously, you're correct. My point was to use them to see how something could be fabricated, not to use them in practice.

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