Running two alternators on same car?

[j-c-c-62]

I want one 5.5lb 50A "Maintenace" alternator mounted low and on the engine. I want another 9lb? 110A alternator off rear DS yoke on an IRS setup. Both would be one wire. Lithium rear mounted battery.
Will this work, or will they fight/hunt? Obviously, the rear one is only useful only when car is moving. It will be re-sized for the load as needed. This is a non-competition no rule restricted track day car, w/EFI, electric FP. electric fans, electric WP. and very limited street/Night use (w/LED's).
No stereo, radio, AC, etc

 

[kiwigtx]

Common ground with both.

Also remember that DC is DC - if you have 12 Volts coming out of both, you cannot harm either one. It wouldn't matter if one puts out a volt or two more than the other.....the battery equalises all that out.

The only issue might be any harmonics or dirty AC that might come out of an alternator - if they put out clean DC you should be fine.

 

[Jeff Peterson]

I’m running 3!

 

[Dave6T4]

I’m running 3!

View attachment 1778399

That guy must have had a battery go dead on him once!

 

[Sixpactogo]

Common ground with both.

Also remember that DC is DC - if you have 12 Volts coming out of both, you cannot harm either one. It wouldn't matter if one puts out a volt or two more than the other.....the battery equalises all that out.

The only issue might be any harmonics or dirty AC that might come out of an alternator - if they put out clean DC you should be fine.

This don't seem right to me......My understanding of alternators is if they are working correctly, they will generate about 17 volts give or take. It is the regulator's job to send that voltage to the battery. It seems to me if you have two alternators and two regulators the regulators have to be in agreement otherwise conflicts will arise. Are you running one regulator? I don't understand the reasoning behind this.

 

[kiwigtx]

This don't seem right to me......My understanding of alternators is if they are working correctly, they will generate about 17 volts give or take. It is the regulator's job to send that voltage to the battery. It seems to me if you have two alternators and two regulators the regulators have to be in agreement otherwise conflicts will arise. Are you running one regulator? I don't understand the reasoning behind this.

DC Voltage is DC Voltage - you can mix 10-18 Volts and it evens out. There may be an issue with needing a separate regulator from each alternator - but the DC Voltages can be combined easily.

I have on site different power supplies with DC Voltages usually 24DC coming in and merging - as long as the Ground (Negative) is commoned up, there are no issues.

The only problems you get is when there is dirty AC floating on the same supply - or harmonics.....and that will only affect equipment connected to the source.

 

[Jeff Peterson]

The "stock" alternator is connected to a heavy duty, adjustable stock style regulator, and still has the feed to the bulkhead the other 2 have internal regs.
I run 2 batts. and the voltage never goes above 14.2, all 3 are connected straight to the batts. which are connected together.
The best part is when I raise the snow plow, only drops to 13.5 volts!

 

[Pikser]

I’m running 3!

View attachment 1778399

Why ?

 

[Jeff Peterson]

Snowplow

 

[wvmarv]

That guy must have had a battery go dead on him once!

 

[j-c-c-62]

Why ?

I glad he piped up, I thought I was going to take some for running two.
But I know why I am running two, but three is above my pay grade, what is the secret sauce here for three? Are they all on same battery?
Back to my opening question, if the output is as claimed near 17 volts, if one alternator sees that 17 volts, will not the other one think, nothing needed and effectively stay silent, or will they electrically bounce back and forth until both are maxed out, to what harm I am not sure?

 

[Jeff Peterson]

As long as the regulators are working properly, they will only put out what’s needed, as I said mine under normal operation show 14.2 volts

 

[Darter6]

Boy I remember those days. Plowing snow for 36 hours straight keeping our lot, employee parking lot,driveway,shipping area and truck lot open.
Not to mention having to plow the owners 1/2 mile driveway to his house.
79 Ford F 250 with one battery. I could have used that set up.

 

[Jeff Peterson]

Boy I remember those days. Plowing snow for 36 hours straight keeping our lot, employee parking lot,driveway,shipping area and truck lot open.
Not to mention having to plow the owners 1/2 mile driveway to his house.
79 Ford F 250 with one battery. I could have used that set up.

First job I ever had was in high school plowing snow for my families trucking/plowing company, we had a small fleet of mid 70’s dodges with the old cable controlled Westerns with atf which flowed like molasses, start out the night fine then the lights start to dim, shut the lights off, later the radio starts to squeal when you raise the plow, shut the heat off, hopefully make it through the morning.
Those memories are what prompted this “overkill” setup.

 

[dvw]

Why not just one large alternator?
Doug

 

[Jeff Peterson]

Why not just one large alternator?
Doug

All of the big 3 offer a dual alternator package with dual batteries.

What is the point of dual alternators?


Dual alternators are more efficient than single alternators, meaning they can produce more power. They also work better in heavy vehicles because they can handle more voltage and RPMs. For example, a single alternator has one electrical output, while a dual alternator has two.

The 3rd one was only added a couple years ago to replace the non functioning a/c and keep the same belt routing.

 

[451Mopar]

I think if the outputs are connected together that one alternator will only be generating power if/when the other alternator can't keep up with the electrical demand, but slight differences in the internal regulator settings could have one alternator doing most of the work. It will work, but the load likely won't be shared between the alternators, more like switched between them upto the point one can't keep up with the load, then both will be providing power.
The alternator with the highest regulator voltage setting will be doing MOST of the work until it can't reach that voltage.
I said MOST, and not ALL because wiring resistance between the two alternators could be a factor in the voltage each regulator "senses". A lot depends on the regulator set points and thermal compensation circuitry.