Author Topic: How do you test the Power supply actual maximum watts?  (Read 613 times)

Offline MrTeaIOT

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How do you test the Power supply actual maximum watts?
« on: February 12, 2018, 10:23:26 AM »
I bought 3 power supply recently from China with good sale price.  When I received then, all have the same size metal box, weight and configuration wiring.  But each rating are different; 30A with 360watts, 42A with 500watts and 50A with 600watts maximum.   First how do we test and make sure that each power supply actually can handle the maximum Watts indicated?  How do we know when the power supply is at the max Watts output?  Is the power supply just shutdown because overloading?  I have Amp meter but not sure how to test it.  Maybe just put the max fuses hope it not blow.

Offline AAH

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Re: How do you test the Power supply actual maximum watts?
« Reply #1 on: February 13, 2018, 12:16:02 AM »
  Theoretically the 2 bigger power supplies should be heavier as the case is used as a heatsink and it's possible the switchmode transformers will be slightly larger but it would only be a tiny weight increase for the transformer.
  The transformer should do 1 of 2 things when you get to an overload current. It should either turn off the output after a short period of overload and then stay off until the power is cycled or alternately it will turn off, wait a bit, power up to check to see if the overload is gone, shutdown if it's still there and continue hiccupping until the overload is no longer there.
  To test the output power for such high current devices is a bit hard. About the only 12V devices that are reasonably easy to apply as a load are car heahlights/driving lights. These convert a lot of the load to light but there's still a heap of heat. If you have easy access to 400-650 W of halogen headlights this is how I would test.
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Offline corey872

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Re: How do you test the Power supply actual maximum watts?
« Reply #2 on: February 13, 2018, 08:41:24 AM »
A 5 gallon bucket of salt water and a couple metal plates could make a 'dummy load' for testing, but personally, I would not stress cheap Chinese power supplies so close to the maximum as to need that type of testing.

If you size the supply to comfortably handle your lights in an 'all on, all white' state, then by default you have some overhead built in as most of the time, you display colors, on/off, flashing, fading sequences, etc.

A more important thing to be concerned with is voltage.  Several posts have suggested nodes having trouble with a full 12V supply and needing to be run at 11.8-11.9V.  So you actually want, or have to adjust your supply to droop slightly below the ratings.
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Offline danj

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Re: How do you test the Power supply actual maximum watts?
« Reply #3 on: February 14, 2018, 10:59:16 AM »
I have hooked up multiple strings of RGBs to load up some of my PSUs and varied the intensity of test settings via the F16 GUI.   I found that even the no name generic PSUs could output significantly higher than rated (e.g., on the order of 400W), at least for short time periods while maintaining voltage really solidly.   I used a "kill-o-watt" that I bought at Harbor Freight on the AC input to my setup to measure power.   That was just an "intellectual exercise"; I typically run at the recommended 80% of rated--about 280W for a 350W PSU.

Offline MrTeaIOT

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Re: How do you test the Power supply actual maximum watts?
« Reply #4 on: February 15, 2018, 08:59:25 AM »
For examples 350 Watts power supply assume running average 280 watts, how much power watts does it draw from AC input side?  Some PSU also lost power due to heat. 

Offline K-State Fan

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Re: How do you test the Power supply actual maximum watts?
« Reply #5 on: February 15, 2018, 09:50:58 AM »
For examples 350 Watts power supply assume running average 280 watts, how much power watts does it draw from AC input side?  Some PSU also lost power due to heat.

I would expect about 330 watts on my power supplies

Offline MrTeaIOT

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Re: How do you test the Power supply actual maximum watts?
« Reply #6 on: February 15, 2018, 09:58:12 AM »
For examples 350 Watts power supply assume running average 280 watts, how much power watts does it draw from AC input side?  Some PSU also lost power due to heat.

I would expect about 330 watts on my power supplies
That's seem to be two much power on the AC input side for 120 AC. 

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Offline K-State Fan

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Re: How do you test the Power supply actual maximum watts?
« Reply #7 on: February 15, 2018, 10:13:50 AM »
For examples 350 Watts power supply assume running average 280 watts, how much power watts does it draw from AC input side?  Some PSU also lost power due to heat.

I would expect about 330 watts on my power supplies
That's seem to be two much power on the AC input side for 120 AC. 

Sent from my SM-G955U using Tapatalk

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Offline k6ccc

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Re: How do you test the Power supply actual maximum watts?
« Reply #8 on: February 15, 2018, 10:15:33 AM »
For examples 350 Watts power supply assume running average 280 watts, how much power watts does it draw from AC input side?  Some PSU also lost power due to heat.

I would expect about 330 watts on my power supplies

That seems a little on the high side for a switching power supply.  For a linear supply, I would buy that, but not a switcher.  In a test that was for something else early this year, I powered up a 12 x 50 pixel tree plus 270 pixel star into full white and took pictures with a FLIR Thermal Imaging Camera.  The purpose was to show how much and what parts of the controller card got warm.  However about 12 minutes into the test, I took a photo of the 350 watt 5V power supply that was powering it all and I have it shown below.  For the test, it was about three hours after sunset,  the ambient temperature was about 60 degrees F and the power supply was sitting out in the open on a concrete driveway.  The supply is a standard Ray Wu 5V 350W supply   I don't know why the temperature scale shows a bottom end of 8 degrees, but the top end appears to be right.  As you can see, the hottest part of the board is the wire terminals on the left end of the case.  I found it interesting that on the IR photo, you can clearly see some of the larger internal components of the power supply through the metal case.
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Offline K-State Fan

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Re: How do you test the Power supply actual maximum watts?
« Reply #9 on: February 15, 2018, 10:24:00 AM »
For examples 350 Watts power supply assume running average 280 watts, how much power watts does it draw from AC input side?  Some PSU also lost power due to heat.

I would expect about 330 watts on my power supplies

That seems a little on the high side for a switching power supply.  For a linear supply, I would buy that, but not a switcher.  In a test that was for something else early this year, I powered up a 12 x 50 pixel tree plus 270 pixel star into full white and took pictures with a FLIR Thermal Imaging Camera.  The purpose was to show how much and what parts of the controller card got warm.  However about 12 minutes into the test, I took a photo of the 350 watt 5V power supply that was powering it all and I have it shown below.  For the test, it was about three hours after sunset,  the ambient temperature was about 60 degrees F and the power supply was sitting out in the open on a concrete driveway.  The supply is a standard Ray Wu 5V 350W supply   I don't know why the temperature scale shows a bottom end of 8 degrees, but the top end appears to be right.  As you can see, the hottest part of the board is the wire terminals on the left end of the case.  I found it interesting that on the IR photo, you can clearly see some of the larger internal components of the power supply through the metal case.

I just used the published 85% EFFICIENCY spec from meanwell to calculate the 330 watts

Offline CaptainMurdoch

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Re: How do you test the Power supply actual maximum watts?
« Reply #10 on: February 15, 2018, 10:28:10 AM »
For examples 350 Watts power supply assume running average 280 watts, how much power watts does it draw from AC input side?  Some PSU also lost power due to heat.

I would expect about 330 watts on my power supplies
That's seem to be two much power on the AC input side for 120 AC. 

You seem to have a misunderstanding of volts, amps, power (watts), and also how they relate to wire sizes.  You need to read some of the latest replies in the wire size thread.

In this thread, to put it simply, "watts = watts".   12v @ 30A = 360 Watts = 120V @ 3A.  That is assuming 100% efficiency in the conversion which our power supplies don't get.  So if you were using a power supply which was 80% efficient, then you would get only 288 Watts on the output side for those 360 Watts on the input side.  To look at that from the opposite direction, in order to generate 360 Watts @ 12V using that 80% efficient power supply, you would need 450 Watts on the input side (360 / 0.8 = 450) which is around 3.75A @ 120V.  This is part of why you can look at a 360 Watt power supply and see that it's input side is rated at using more than 3A @ 120V.
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Offline MrTeaIOT

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Re: How do you test the Power supply actual maximum watts?
« Reply #11 on: February 15, 2018, 10:29:46 AM »
It did stated is a Switcher power supply.  What is that mean?  On your k6ccc last post do you put a meter to check the Watts drawn on the AC input side?  I am worry too many power supplies running  will get a surprise (higher) electric bills.




EDIT: updated by CaptainMurdoch to make the font a readable size.
« Last Edit: February 15, 2018, 10:32:50 AM by CaptainMurdoch »

Offline CaptainMurdoch

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Re: How do you test the Power supply actual maximum watts?
« Reply #12 on: February 15, 2018, 10:34:46 AM »
It did stated is a Switcher power supply.  What is that mean?  On your k6ccc last post do you put a meter to check the Watts drawn on the AC input side?  I am worry too many power supplies running  will get a surprise (higher) electric bills.

What program are you using to post?  This is the 3rd or 4th post I have seen from you today with the font size set to 2px which is so small it is unreadable unless someone quotes your message and can see the original text.

Offline CaptainMurdoch

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Re: How do you test the Power supply actual maximum watts?
« Reply #13 on: February 15, 2018, 10:35:07 AM »
I would expect about 330 watts on my power supplies

That seems a little on the high side for a switching power supply.

What kind of efficiency are you expecting out of these power supplies?  I might expect the Meanwell to hit 85% as K-State-Fan noted, but I would expect a bit lower from the generic power supplies a lot of people are using.

Online pixelpuppy

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Re: How do you test the Power supply actual maximum watts?
« Reply #14 on: February 15, 2018, 10:40:30 AM »

What program are you using to post?  This is the 3rd or 4th post I have seen from you today with the font size set to 2px which is so small it is unreadable unless someone quotes your message and can see the original text.

I don't know what MrTeaIOT is using, but That happens a lot to me and I've seen it with many other people too.  (in fact is just happened).   I'm using Google Chrome browser.

It only happens with this forum.  Something is weird with this forum's software.   I first noticed it a long time ago and just got used to fixing the font before I click the "post" button (quick trick I use is ctrl-A, then drop-down font-size-10)
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