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Old 06-14-2009, 07:04 PM   #41 (permalink)
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Quote:
Originally Posted by ShadeTreeMech View Post

If you want to reduce the alternator load, put in a bunch of solar panels on the roof and dashboard.
yeh, rip out the sunroof and fit a 30w panel, and run the alternator at 1/2 speed (and a fraction of the belt tension too).
i ran without the belt on too, during some sunny spells last summer
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Old 07-12-2009, 10:42 AM   #42 (permalink)
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wind driven alternator

I have a 2004 dodge ram PU the alternator is wind driven. using a small squirrel cage fan ducted to the fog light mount in the bumper.naturally it only charges while in motion. still using factory installed battery now almost 6 years old.
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Old 07-14-2009, 04:06 PM   #43 (permalink)
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Originally Posted by kr4ua View Post
I have a 2004 dodge ram PU the alternator is wind driven. using a small squirrel cage fan ducted to the fog light mount in the bumper.naturally it only charges while in motion. still using factory installed battery now almost 6 years old.
that sounds interesting I would love to see pictures
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Old 07-15-2009, 04:58 AM   #44 (permalink)
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I've been alternator free for about a year now. I'm getting at least 10% better FE.

My current set up is a 12V costco deep cycle that I got for $49 at the end of season clearance and a used 6V trojan t-105 that I got free. I have them set up in series for 18V. Assuming a 10% improvement that battery was paid for after 10 $60 fill ups. The battery is only discharged about 10% for each trip I make and should last for over 1000 cycles. I already had an automatic battery charger but you can pick them up for $30 if you look for deals.

I am running at 18V to keep the spark nice and hot and the fuel pump at max pressure.

FE gains from alternator disconnect have been shown on this site by metro mpg and others to give 10% better mpg. That ranks up there as one of the biggest single gains in the ecomod list. And that gain was at 12V. They would probably get a bigger gain at 14.5+V.

A deep cycle battery that is only discharged 50% should last well over 1000 cycles. Chart of Depth of cycles vs life.

Alternators are at best 40-50% efficient so for every watt produced the engine has to produce more than double the watts not including the belt friction.

Just to keep the average car running +/- 18A turns into about one HP when you do the math which is drawn at all engine speeds including idle. Idle happens to be the most inefficient engine speed. Remember too, you have to replace the energy lost to starting: 300+ amps at the best of times.

Once you learn how to figure out your amp draw you can estimate your battery life just like with gas. You can even get a battery gauge just like a fuel gauge showing % discharge. Or keep the original starting battery in the car as a spare. I have never run out of battery juice myself.

The best thing is I get to say I have a hybrid.
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Old 07-16-2009, 12:29 PM   #45 (permalink)
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I still like the idea of a solar panel and a wind powered alternator.

both of those sound like easy solutions without costing a ton for batteries.
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Old 07-16-2009, 12:34 PM   #46 (permalink)
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Quote:
Originally Posted by metalshark View Post
I still like the idea of a solar panel and a wind powered alternator.

both of those sound like easy solutions without costing a ton for batteries.
I'd like to see pictures and some non-biased data from anyone who claims FE improvements from a wind-driven alternator operating while they're driving.

*Maybe* just *maybe* it would work out in a normally high-turbulence area like the fog light holes, but I still have my doubts.

Then, when you consider how much "power" wind contains at speed and density, vs the amount of "power" it takes to spin the alternator under load, I'm almost sure it just won't work with such a small area for the air to act upon.

In fact, I'm calling BS until there's evidence otherwise.
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Old 07-16-2009, 01:09 PM   #47 (permalink)
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Im not saying Ive done it but kr4ua said he did. like I said before I would love to see pictures of it working.

It sounds like it would be plausible at speed over 50 with a big enough turbine.

I once had an idea of an alternator driven by exhaust force.. using a turbo exhaust housing and make custom fittings for an alternator to be place at a cool distance.
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Old 07-16-2009, 02:14 PM   #48 (permalink)
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Quote:
Originally Posted by metalshark View Post
Im not saying Ive done it but kr4ua said he did. like I said before I would love to see pictures of it working.

It sounds like it would be plausible at speed over 50 with a big enough turbine.

I once had an idea of an alternator driven by exhaust force.. using a turbo exhaust housing and make custom fittings for an alternator to be place at a cool distance.
What would actually happen is that (possibly unless it's in a place of high turbulence already) the blades of the turbine or cage fan would just increase the overall drag coefficient, which would make the speed at which drag becomes an issue even lower than ~45mph.

The exhaust driven turbine-alternator has been done by a company... we're awaiting mass production or ultimate failure.

Regarding the wind-driven alternator -

Here's the formula you need to determine that it will or won't work:

P = 0.5 x rho x A x Cp x V3 x Ng x Nb

where:
P = power in watts (746 watts = 1 hp) (1,000 watts = 1 kilowatt)
rho = air density (about 1.225 kg/m3 at sea level, less higher up)
A = rotor swept area, exposed to the wind (m2)
Cp = Coefficient of performance (.59 {Betz limit} is the maximum thoretically possible, .35 for a good design)
V = wind speed in meters/sec (20 mph = 9 m/s)
Ng = generator efficiency (50% for car alternator, 80% or possibly more for a permanent magnet generator or grid-connected induction generator)
Nb = gearbox/bearings efficiency (depends, could be as high as 95% if good)


Assuming the best possible circumstances, and 100% of the Betz Limit -

(Work the formula from left to right)

0.5*RHO(1.225) = .6125
(That foglight hole isn't even .5M^2, but we'll use it anyway, since there are turbine designs that have more than "face value" for their area)
.6125*A(.5M^2) = .6125*0.25 = 0.153125

0.153125 * Cp(.59) (Using Betz Limit) = 0.09034375

0.09034375*V3(WindSpeed, or Vehicle speed, in this case, in M/S) (45mph = 20.1168 meters / second) (20.1168 meters / second * 3 = 60.4m/s

0.09034375*60.4 = 5.4567625

5.4567625*Ng (we'll assume the alternator is replaced with a permanent magnet generator, at 80% efficiency)

5.4567625*0.8 = 4.36541

4.36541*Nb (again, assume space age efficiency here)

4.36541*0.95 = 4.1471395

So P = 4.1471395, or about 4.15 watts.

4.15 WATTS!, and that's assuming the best case scenario.

I'm reasonably satisfied to say that this claim is COMPLETELY false, unless I've overlooked something.
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Old 07-16-2009, 05:40 PM   #49 (permalink)
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You gave the foglight hole half a square meter!?

Oh, you so crazy. Or generous. Or - and this isn't completely outside the realm of possibility (though it is making an escape attempt) - that really is one mother of a foglight.

Any turbine that claims more than its face area is working from the maxim regarding fools and their money.
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Old 07-16-2009, 09:27 PM   #50 (permalink)
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If the air-driven turbine was enough to do anything useful, the performance-oriented crowd would already be using it to force air into the engine. You'd have cold air intakes that stick out from the grille if that really worked. Sure, it might provide a little extra, but it's minimal at most.

The exhaust-powered alternator is being developed by ThinGap, and is definitely a great idea - but it will probably cost too much to be worth the MPG gains, unless it starts coming as a standard option as new vehicles.

The wind-driven alternator that was posted definitely sounds bogus. And the battery lasting 6 years is cool, but probably has nothing to do with a little fan in the fog light hole.

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