Thread: Crazy Idea

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I have this crazy idea for a cheap solution to compensate for a voltage problem. Since I, like many others that may read this thread, have been making ongoing modifications to my ride, some of these modifications require greater than normal current draw from the battery. For instance, electric fuel pump, high power ignition, and the biggest culprit, in my case, electric radiator fans.

I have recently installed in the past couple months Derale dual electric fans. And boy do they work great for keeping the radiator cool. I have them set up so that one kicks on at about 150 - 160 degrees F and the other kicks on somewhere around 190F. The second fan also kicks on whenever I run the A/C. Biggest reason for making the switch to electric fans was because the engine used to over heat whenever I ran the A/C and I was sitting at a traffic light. Not cool in a 90+ climate (pun intended).

Anyway back to the issue. Now that I have these nifty electric fans, that pull 2000cfm each through the radiator, they draw about 20 - 25amps each. When sitting at the traffic light, this makes my voltage drop to 11.5V with one fan running and almost down to 11V with both running. Then you add headlights, etc. Keep in mind I have an 180amp alternator so charging the system is not a problem. Once I get going, voltage pops right back up to 14.4+ almost immediately. The reason this is a problem is because the low voltage adversely affects the ignition system. There is a little stutter until the voltage gets back above 13V.

Now for my crazy idea/solution. Of course the correct way to remedy the situation would be to drop about $450 and buy a Jacobs Accuvolt to maintain a constant system voltage. Now, I like to tinker and I don't want to spend $450 on this electronic gizmo, as cool as it may be, so this is what I came up with... I am going to take my old alternator (it's 80amp) and I am going to run it off of an electric motor, the same motor that comes with the Moroso or Mr. Gasket electric water pump conversion. I am going to wire it to a relay so that when the ignition key turns on, the motor is activated along with the alternator and this will give me just the little bump I need to keep the system around 14V when I am stopped, in gear, with all fans and headlights, everything running. Of course I will have to fabricate a little mount for the motor and the alternator, and permanently attach it to the vehicle somehow... but that's part of the fun.

Anyway, let me know what you think of my crazy idea.

I gotta reply.

Think about an electric motor running an alternator. If you use the alternator output to run the motor, it wont work because of a little word called "efficiency." If it did work, you would have perpetual motion.

Anyway, the motor takes more energy in than it puts out. The difference is consumed by friction and heat production. The alternator is the same.....more in than out. So we have to add more to the motor to get less from the alternator. Think of it as you working 8 hours for your wife to shop 8 hours....it aint gonna work.

Given you would have to add power, where would it come from? From the system you now have that is already running low.

What you might explore is a dual battery setup where the auxillary battery can be used to agument the system. The system would charge both batteries but the auxillary could supply a little extra power during a peak draw. A second battery is more compact than a motor/alternator too.

you need a two speed drive for your alternator. When I was an engineer at ford I proposed a drive system like they used 0n the 1957 Thunderbird paxton supercharger. After I left ford they used the system for a while in 84 on the bird to drive the alternator, power steering and ac compressor at higher rpm at low engine idle then switch to low speed on the highway when the engine rpm is up. the accessory speeds would be at normal speed. I made the proposal but have never searched out a car to see how they actually did it.

Congratulations!!! If your idea works, you have discovered the key to perpetual motion.----Need more electricity?---just run a second alternator off an electric motor. Think about what your saying!!!! Its a law of physics that you can't get something for nothing. The more power you use to run a second alternator off an electric motor, the higher the demand on your electrical system goes. If you are not carefull you will be like the legendary FUFU bird, that flies in ever diminishing circles untill it flies up its own butt and disapears.

Along with some of the other good ideas, you just might be able to put a smaller pulley on the altenator to get the speed up at idle. If you don't turn outrageous rpms on your motor that will likely help.

kind of off topic but maybe not when i was young my dad used to have problems with alternators on his tractor we had a white tractor with a 3208 engine pretty big unit pulling a big john deer pull type combine . we would combine all night once i was old enough , i had rigged up 4 - 3 wide banks of 7 inch halogen automotive (12 lights) headlights. 2 sets on the tracor and 2 on the combine this plus the factory lights lit up the county as i would run the high and low beams at the same time for more flood light action.
to get a idea what this would draw i had to use light welder cable and jumpers onto the battery to run this monster. hook them up when it gets good and dark and instant sun this semed to be ok for a while we had already one of the huge dodge style 120 amp alternators on the tractor . it actually held out pretty good till poof up it went.
we got another alternator hooked up and i took a another older gm alternator and instead of running it off a regulator i ran it direct as when i hooked up the lights it activated the alternator and away we went . they burnt out too but it would still last a pretty long time as only using at night . had lots of the old style gm alternators as could get them for 10.00 apiece .
i think the dual battery idea and a big alternator would work better in this application as it is perodic high amp usage as opposed to putting a huge draw on a system and leaving it there.
already had 2 huge batteries on a tractor anyways.

that sounds about like the thread about making a blower out of a elec. motor. its ant gonna happen. if that was possible ever hot rod in the world would have moved the alt. so you couldnt see it. i hate to tell this, but i tried to do it about 20 yrs ago. the elec. motor will turn the alt. by itself just fine, just dont put a load on it. it want work.

Interesting comments... I reallize i

"Think about an electric motor running an alternator. If you use the alternator output to run the motor, it wont work because of a little word called "efficiency." If it did work, you would have perpetual motion."

At the bottom of my post it says "tanstaafl" That stands for "there ain't no such thing as a free lunch" ROBOT had it right- perpetual motion doesn't work in THIS universe.
You might try running your fans from the battery to use it as a buffer between your alternator and ignition. I'm no electrical expert by a lonnnnng shot, but that might cause less of a drain on your ignition. Be sure to include an inline fuse!

What you might be looking for is a contant-velocity drive, these are used on some snowmobiles and ATCs in place of a conventional clutch and gearbox.

Essentially the pulley is built with two opposed cones tapering inwards forming a "V" between them. A wide and thick "V" belt sits between the two cones. As the speed changes the cones move together or apart with the belt seeking a different ride height in the "V" groove. The different ride height generates the variable drive ratio, 4:1 is quite feasible. A simple flying weight governor (similar to your advance plate in the distributor) drives the cones in and out to regulate the speed.

My truck has two 135A alternators standard, probably as Fords answer to this problem. Two alternators driven off the same belt with identical pulley diameters should share the current fairly evenly. Since the current per alternator has been halved their output voltage should increase - hopefully up to the desired voltage. This is a more practical solution and provides redundancy as well.

Cheers, Mark

Aagh... my son pushed buttons on the keyboard...
Anyway, Interesting comments. I reallize it is not going to charge the system and was not the goal behind this idea. The goal was to simply stablize the voltage of the system when the engine isn't running fast enough to do it. Not an attempt to create so called "perpetual motion", but just somehow keep the voltage up when the engine isn't spinning fast enough to do the job.

I really like that 2 speed drive idea.

On the dual battery setup mentioned... you mean to separate the fans from the ignition so that the ignition is running off of the battery with the least load?

"modifications require greater than normal current draw For instance, electric fuel pump, high power ignition, and the biggest culprit, in my case, electric radiator fans".

i think somebody is pulling somebodys leg. anyway. these are his modifications, and he has a 185 amp. alt and need more. every hot rod here has most of these mods. and i dont think you need all that alt. 100A about as big as ive ever had, and i dont have no bat problems. now somebody have 2 -135A alt. you could run a house off this kind of amps. i can see that on your show car now.

Mike,

My Ford F350 truck comes factory stock with two 135A alternators. I don't think most folk need 270A of power but it does help satisfy the requirement of 130A or so while the engine is idling. That is the reason I brought it up. Since I have a 2500 Watt inverter to power up, at 12V this draws 200A. Without the alternators being able to keep up with this demand the batteries, even duals, would be depleted soon. This is not a "hot rod" application though, but a work truck.

Cheers, Mark

that was the point that i was trying to get across why would a hot rod need all of that amp. work truck you need what you need.

Run your second alt off your driveshaft, under the car, then have an extra deep cycle optima battery in the rear, like the trunk or if this is your van, the rear cargo or even mounted under the floor with an access panal to get to it, just make shure it is encased, wire in a simple fuse block/ relay block into an assesable place, wire your fans into that battery fuse box, yes the battery wouldn't charge when stopped but, the deep cycle battery will hold good, until the light turns green. Of course, couldn't it be a relay not hooked up right and drawing too many amps?