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Discussion Starter #1
I've done some research and it seems that the best fit for my 1963 Chevy II is a SPAL 11" dual fan set up. It will pull up to 39 amps, and that seems like a heavy load. My question is :

1) How strong of an alternator do I need?

2) I'm not running any other high amp stuff. what will the effect of a powerful alternator on the rest of the electrical? is there other stuff I should upgrade along with the alt?

3) Should I get a stronger battery?

4) am i opening a can of worms that I'll regret later:rolleyes:?

Thanks for your input, love the site!
Olaf in Berkeley
 

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The alternator output (amperage) needs to be higher than what the load is. If you have a 100A load and have a 80A alternator, then this remaining 20A will come off of the battery BUT since a battery is a storage device eventually it can no longer output this 20A of output and then the 100A load is trying to run off of 80A and things will not work properly.
A voltage regulator monitors what the alternator needs to put out so even with an alternator that can output 200A of power and then having a load of something like 30A, the regulator will have the alternator output 30A and all is fine. If later more power is needed the alternator might put out 90A to keep up with the load. My opinion is buy an alternator that is larger than what you need. If you buy one that might fit the bill for what you have now then later add more to the system you are swapping alternators out again. Just like the power company running a 200A line to your house. You may never need it BUT it's there for additional things later (up to a point).

If you get a larger battery then this places additional loads on the alternator to charge it. Get a battery large enough to easily start the engine and all should be good.

Whenever you put something larger in a car, you also want to make sure the rest of the system can handle things. The factory is only going to design their system to be just enough so if later you add a higher output alternator, upgrade the wiring to support this change.

Like anything else you can be opening a can of worms BUT if you think the whole thing through, ask questions when in doubt, have people explain things that make sense and work, then you should be able to do it. Sometimes electrical things can scare a person but you just need to respect what it can do and whatever you do with it, do it properly.

There is plenty of info out there on how alternators work but keep in mind at lower engine RPM (like a low idle) some alternators will not put out what they can unless they are spun faster.

Jim
 

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I am changing out the radator in my 66 Nova SS and putting in aluminum with twin electric fans. Before I did this the person that had the car before me had change the alternator to a 100 amp. When you would turn the air on the volt meter would drop. I decide to get a 140 amp alternator to supply enough power to the twin fans. One thing I found on doing this was that the wiring wasn't big enough for the amps when everything was turned on. I changed the wiring and the volt meter doesn't drop now. I would check the size of wiring you have going from the alternator to the Battery. This needs to be no smaller than 12 ga.
 

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Discussion Starter #4
Thanks guys

this is looking like it's going to be more of a project than I'd hoped. I appreciate the help, and i'll post progress as it happens.
 

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Ok, Ill chime in..

A 39 amp draw might not be all the time if the fan is variable speed. And even if its not variable speed it still wont be on all the time. It should have a temp sensor that will shut it off when the temps are lowered.

So the 39 amp number is prolly when its running maxed out.

An 80 amp alt can easily supply an electrical system that was determined to need 150 amps at peak load.

Example? If you were to figure out what the peak load of your car's electrical system needed, thats with ALL the electrical devices ON at the same time and drawing max current then you have "peak" demand. You will never run into a sitch where you are using peak current. That would mean using the power windows (all the time), A/C on full, all the lighting on (interior and exterior), horn on, and the list goes on (power seats, EFI, windshield wipers, stereo... ETC...).

The peak load is a great place to start when determining what alt you need. Im not sure of how much it can be altered. Like if you determine your peak load is 150 amps and what size alt will be sufficient. But I do know that you dont need a 150 amp alt for a peak load of 150 amps.

And Im talking about a car with a "standard" stereo. Not one of the cars we see with four large amps and some massive current needs. Just a regular car with intermittent current draws along with some continuous current drawing parts (like an EFI system).

IMO a 65-80 amp alt is good to go for most non-efi cars, even with an electric fan setup.

Your fan wont be on all the time, it will cycle. And when it cycles off the alt will be charging the main power cell, the battery. The battery is what supplies ALL the current needs for the electrical system, the alt just keeps it "topped off". And batteries can handle some heavy current draw, yer starter is a biggy.

Peeps get caught up with the high current alts I think because of the media (mags and the stereo folks).

No need to go all critical with high amp alts for simple cars. GM does not so I think the drama with high current alts is kinda over played.

Umm? And voltage regulators? Someone talked about voltage regulators and how they monitor what the alt needs to put out.

A voltage regulator is just THAT, it controls the voltage. Your alt will produce a wide range of voltages depending on how fast it is spinning. They are designed to output at lease the lowest value of voltage for idling speeds. That would be fine if we idled the engine everywhere. But we dont. As the rpm of the alt rotor increases above idle it will also increase its voltage, thats just how alternators (AC) and generators (DC) work. More rotational speed means a higher voltage. Our cars need a certain voltage (13-14 or so). The voltage regulator WONT limit current from the alt to the batt. All it does is regulate the voltage.

Automobile voltage regulators are pretty primitive. They regulate the voltage to within volts. There are many voltage regulators that are tuned to milli and micro volts. But thats a diff story.

The car voltage regulator is in place to keep the alt from "cooking" the batt and to keep higher voltages off the system.

For example. You can have a 24 volt regulator on the end of your alt, it wont care, it will feed 24 volts to the batt and all the system when its running.

Problem? The batt will charge just fine. Even though its a 12 volt cell. But it WILL get damaged over time. Specially if its a "cheap" battery. It might short while charging and cook some plates. The 24 volts might be just enough to bridge the insulating gap internally. But with modern batts prolly not. You can put a 24vdc charge on them. But it will be a fast HOT cook for the batt. Its like putting a charger on start, 50 amps for the entire time. OHMs law.

Um, if you disconnect the alt from the system even though you were pumping in 24 volts the battery will still give you the 12vdc that you need. Its a 12 volt battery. You can charge a 12 vdc battery with 24 vdc and it will still provide 12 vdc. Thats just the way it is. The batt can handle more input voltage (to a point). But it will always supply the voltage (12-14) that its plates are configured for.

The car battery is more than a sink for the excess current that the alt provides. The battery is more important than folks think. Its a regulator in a way. It provides a constant voltage (more than the voltage regulator for the alt does). Its a constant voltage supply (due to the amount of plates) and a firm and stable DC that many electrical systems need. The alt dose NOT power your car, the battery does. JR
 

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I am changing out the radator in my 66 Nova SS and putting in aluminum with twin electric fans. Before I did this the person that had the car before me had change the alternator to a 100 amp. When you would turn the air on the volt meter would drop. I decide to get a 140 amp alternator to supply enough power to the twin fans. One thing I found on doing this was that the wiring wasn't big enough for the amps when everything was turned on. I changed the wiring and the volt meter doesn't drop now. I would check the size of wiring you have going from the alternator to the Battery. This needs to be no smaller than 12 ga.
I run 8 gauge to the solenoid, and also on up to the alternator. Battery & solenoid are in the trunk.

Grounds also need to be beefed up. They are just as vital as hot leads.
 

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Oh, and the voltage drop you see on a gauge is common. The voltage gauges are to far down the line.

They see a system voltage drop, meaning all the line drop. A good meter would be tapped right at the battery. In that case you prolly wont see a voltage drop.

What the gauges are seeing is the drop across the point where the gauge is connected.

An example. If you were to connect the line for the gauge in the starting circuit, yup reading the starters voltage drop you would see it go to close to zero while staring.

I dont have much use for voltage gauges unless they are across the batt..... JR
 

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twin spals entropy crossflow

I've done some research and it seems that the best fit for my 1963 Chevy II is a SPAL 11" dual fan set up. It will pull up to 39 amps, and that seems like a heavy load. My question is :

1) How strong of an alternator do I need?

2) I'm not running any other high amp stuff. what will the effect of a powerful alternator on the rest of the electrical? is there other stuff I should upgrade along with the alt?

3) Should I get a stronger battery?

4) am i opening a can of worms that I'll regret later:rolleyes:?

Thanks for your input, love the site!
Olaf in Berkeley
Recently I needed to replace a very tired original style radiator in a 63 ss 383 stroker/(the radiator I was replacing was pulled from a 64 wagon w factory ac ,I had it modified to 4 row in early eighties)I had read some good reviews on vette and camaro forums on entropy radiators.I bought the complete set up off ebay to include: crossflow radiator, dual spal pullers, sender and relays and wiring/ very high quality stuff beautifull welds.Unfortunately to install this radiator I had to relocate the battery to the trunk(this is something I always wanted to do anyways) In the early nineties I had installed a powermaster one wire alternator rated @ 120 amps. This car has no high current drawing options .The alternator output wire is 8 guage.When the fans come on the volt meter dips from 14 volts to 12 then comes back to 14 I think this is normal. The car starts right up all the time and the temperature guage never goes above 190 degrees. ( I ran 2/0 marine cable from the battery + to a master disconnect switch in the trunk then to the starter . I ran 1/0 welding cable (very cheap to buy)from battery - first to the frame @ rear of car then to rear of engine block. If i remove the ground cable from the engine block it will crank just as fast ......Sometimes you start a project and their is a domino effect just plan ahead like I didn't and you'll be fine....
 
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