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# hooking 3 power supplies in parallel?

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#### Artephius

##### New Member
Hi,

I have three server power supplies that claim to be capable of 22 amps each at 12 volts. Can I hook them up in parallel and get something around 66amps at 12 volts or would this be a little more complicated?

Thanks

If they are identical and your good with hacking the feedback circuits from two of them so that they get their reference signals from the third one its possible.

Its not easy or all that reliable in may cases.

What do you need 12 volts at 66 amps for?

If they are identical and your good with hacking the feedback circuits from two of them so that they get their reference signals from the third one its possible.

Hm, well they are identical but I certainly don't know how to do that. I was hoping I could isolate them from each other somehow (if necessary) and then only combine the power at the point of the load. I don't know too much about electronics unfortunately.

I'm building a large electrolyzer to make hydrogen and I designed it to run on 12-13 volts so it might draw quite a few amps since it's large. I can't increase the voltage to it though or else it just gets wasted as heat. I could change the configuration to make it run on 120vdc and just rectify my house current but then it wouldn't run in my car (and I'd have to buy more expensive stainless steel.)

A simple, though wasteful way, to do it is to put ballast resistors in series with each output. The voltage drop across the resistor should be larger than your voltage imbalance.

Read the voltages from each individual supply. Let's say that the maximum difference is 0.3 volts. Then you design the resistors to drop about 0.5 volts. at full load.
Which by ohm's law means a resistor value of 0.5/22 = 22.7 miliohm, and each one would dissipate 11 watts. You'll need 20 watt resistors for reliability.

Another drawback is that the voltge regulation degrades, but for your application, that may not be of any consequence.

Most computer power supplies have all of the voltage control feed back referenced to the 5 and 3.3 volt sources. The 12 volt outputs are very loosely regulated and may allow for a considerable amount of power to be pulled off of them when combined without any real ill effects.
Just tie all the same voltage outputs together and see what happens.

The highest output one Will do the most work until it gets pulled down to the point the next one starts putting out power and then they both get pulled down until the third one starts carrying a load also.
Being all three are identical the actual voltage variations between them may be only a be a few Millivolts at no load so they will likely just naturally balance themselves out when loaded down.

But unfortunately the HHO police will be here shortly to arrest this thread from going any further.

(but its still fun to watch though)

Most computer power supplies have all of the voltage control feed back referenced to the 5 and 3.3 volt sources. The 12 volt outputs are very loosely regulated and may allow for a considerable amount of power to be pulled off of them when combined without any real ill effects.
Just tie all the same voltage outputs together and see what happens.

The highest output one Will do the most work until it gets pulled down to the point the next one starts putting out power and then they both get pulled down until the third one starts carrying a load also.
Being all three are identical the actual voltage variations between them may be only a be a few Millivolts at no load so they will likely just naturally balance themselves out when loaded down.

So you don't think it would try to draw too much from one before the other starts to kick in?

But unfortunately the HHO police will be here shortly to arrest this thread from going any further.

(but its still fun to watch though)

But why? This is not an HHO thread... this is a crazy power supply idea thread I imagine you guys do probably get alot of HHO people in here asking about PWM's and such though lol

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Its worth trying. If you have a good volt meter check the voltage differences between each of them. If its less than around .1 volts from highest to lowest it should work. If not they will likely just shut down and protect themselves. I have paralleled old computer power supplies before without problems.

As far as this being an HHO thread well you did say your electrolyzing water into hydrogen and mentioned needing it to work on 12 volts so it would work with your car.
That could be interpreted as a HHO system here.

I rather like the challenges of non conventional thought and research myself but you will find a few here that are going to get a bit nuts and be rather pushy about their views on it though so be prepared.

Fortunately as long as its kept reasonably scientific it will be allowed here. Most of us do like learning about odd stuff that others are experimenting with.

Its worth trying. If you have a good volt meter check the voltage differences between each of them. If its less than around .1 volts from highest to lowest it should work. If not they will likely just shut down and protect themselves. I have paralleled old computer power supplies before without problems.
Alright. I did test them (without any load) and they were all 12.34 or 12.35. I don't know what happens under load though. At the moment I don't have anything to load them with or I'd check. I'll give it a try though once my 'device' is built.

As far as this being an HHO thread well you did say your electrolyzing water into hydrogen and mentioned needing it to work on 12 volts so it would work with your car.
That could be interpreted as a HHO system here.

I rather like the challenges of non conventional thought and research myself but you will find a few here that are going to get a bit nuts and be rather pushy about their views on it though so be prepared.

Fortunately as long as its kept reasonably scientific it will be allowed here. Most of us do like learning about odd stuff that others are experimenting with.

Got it. I'll ask HHO questions to the HHO community elsewhere.

Thanks for the quick help!

my adwise dont try it in parellel if you can use 36V then make them in series it will work comfortably, putting two or more power supply in parellel is not a practicable one and the load couldnt be equally hsared, also when one goes over load, it turns off if protection is there then it will lead for others too to turn off. if you put resistors as sugested by some one still you may find hard time.

if you wanan stick on 12V only then there are cheap modules available from china i have used them for some application, just check on ebay.

Don't hook computer power supplies in series. (Unless you fully understand how to isolate the Earth lines and you understand the shock hazard.)

The 0V (black) wires are connected to the frame, and to the Earth line on the power cord. If you hook any +12V wire (yellow) to the 0V (black) wire of any other PC power supply, it will short circuit it.

Hopefully this would simply trigger the protection circuit or at least blow the fuse instead of starting a fire.

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