Combining 2 Alternators (Same Brand) in parallel for enhancing o/p current

Thread Starter

aj0092

Joined Dec 26, 2016
4
Our application requires maximum output, for this we are installing two alternators(Same brand (28V / 185A)) in the vehicle. We are replacing vehicle stock alternator and adding another additional alternator. In this way both alternators will provide maximum output to our load (Alternator charges the vehicle battery, once its charged, both alternators will contribute to my load).
I am using battery equalizer so that my vehicle (Land Cruiser 2015) battery will also work in addition to external batteries (with same specs but different from stock vehicle battery) which I have installed for my load (high power lights).

My question is if I install two alternators in parallel (with separate regulators), will it damage the batteries? or any other hazards ?

Will this fulfill my requirement for having maximum output.

I have attached the picture of my circuit.
 

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crutschow

Joined Mar 14, 2008
34,715
Would not one alternator tend to provide all the power until it reaches it's maximum current output and then the one with the slighter lower regulated voltage would start working?
I think one alternator working at it's maximum output would be problematic.
 

WBahn

Joined Mar 31, 2012
30,254
Would not one alternator tend to provide all the power until it reaches it's maximum current output and then the one with the slighter lower regulated voltage would start working?
I think one alternator working at it's maximum output would be problematic.
This will likely be the result, but may not be a problem. Consider if the system was such that it only needed one alternator instead of two, but that one alternator would be working at near max output all the time. As long as the alternator was spec'ed to handle that load, life is good.

If both alternators/regulators are matches so that they both come up at roughly the same rate, then you can run into instability because one alternator dips and the other alternator tries to increase, but then the matching tries to make it decrease and the other one spikes.

This is a common problem in hydraulic systems that have dual pumps with the result being that you get oscillations that can destroy the equipment. The solution is simple -- put a check valve in line with one of the pumps so that the other pump provides all of the fluid until the demand exceeds its capacity, at which point the pressure drops enough to let the other pump start pushing fluid into the system and it regulates the flow while the first pump operates balls-out at its limits. The 3000 psi Utility System on the F-15 is just like this, with a 250 psi check valve in the output of one of the pump output lines. Each pump can deliver about 57 gph so the first pump delivers the first 57 gph at 3000 psi and the second then lets the system deliver up to 114 gph but at a reduces system pressure of about 2750 psi.
 

MaxHeadRoom

Joined Jul 18, 2013
28,780
Auto alternators operate on maintaining a constant voltage.
They should be close enough not to cause any problems of one carrying any more load than the other, IMO.
Max.
 

Thread Starter

aj0092

Joined Dec 26, 2016
4
Firstly thank you all for replying. Max I have also attached the schematic diagram in the questions kindly have a look at it. Also, my real concern is that when I will connect the two alternators in parallel, since they have the exact same brand with the exact same specifications my concern is that will they cause any sparks or any other damage?

Thank you all again for replying. I am doing this for the first time that is why I want to be 100% sure.

Thanks.
 

bwilliams60

Joined Nov 18, 2012
1,450
When you are placing two alternators on the same system, you want to make sure that the wiring to each is of the same length and size. That way you will not tax one more than the other. Just keep everything equadistant from your supply and you shouldnt have any problems.
 
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