Can this power distribution board will handle 1200W? - Page 1
Forum section: electronics / beginners

author: gotofbi
author_rank: Contributor
timestamp: August 06, 2023, 06:24:03 am
content: Hi,I am planning to build 24v 1200W power supply using 2x 600W HP server power supply.After building the power supply, I am planning to hook 8x of 150w devices (this is theorical max output and mostly will stay around 100-120W)To connect those devices to power supply, I am thinking of using this power distribution board from aliexpress.

author: Xena E
author_rank: Frequent Contributor
timestamp: August 06, 2023, 07:45:53 am
content: First answer is no. 1200W at 24Volts is 50Amps.Each outlet will also be passing over six amps.There is no over current protection, either the total load or individual loads.Care must be taken with high current at DC regards ratings of switching and protective devices, contact arcing and sustained arcing in poorly rated overload protection and switching is the problem.As a suggestion, if, you want to do this system with easily/cheaply obtainable parts look more at the suitability of using equipment for electrical distribution in trucks etc.,Cables should be coordinated with reference to the total likely loads, and volt drop caused by the length of them. If all outlets are un protected from over current, all cables will have to be rated up to the level of protection provided at source: Google is your friend here.The biggest negative outcome here is fire.

author: Manul
author_rank: Super Contributor
timestamp: August 06, 2023, 09:03:22 am
content: Quote from: gotofbi on August 06, 2023, 06:24:03 amAre you implying that you will connected them in series? Are you aware of the associated issues?Regarding you question, first of all, you should not think about watts here, but amps. So it's 50A max current. No, the pictured PCB does not look like adequate and reliable for such current. Bannana plugs are also not rated for 50A.I think you should get quality crimp terminals, crimp them well and get at least 50A rated terminal block from electrical hardware shop.For the wires, again, 50A is the key number.

author: gotofbi
author_rank: Contributor
timestamp: August 06, 2023, 10:09:32 am
content: Thank you @Xena E and @ManualHow about this design? (I attached new photo)This example used 8AWG wire which is rated 50Amp and used XT60 connector which is rated 60AmpAnd connect this into distribution board that divides into 8 different XT60 connectors.I will connect this distribution board to power supply with 8AWG wire as well.Thanks!!

author: Xena E
author_rank: Frequent Contributor
timestamp: August 06, 2023, 12:22:33 pm
content: Yes better.Without individual over current protection you will still need to use the fully rated cable throughout.

author: Jeroen3
author_rank: Super Contributor
timestamp: August 06, 2023, 02:05:30 pm
content: Find a fuse board for campers or caravans.Careful, the china export probability is very high, especially for the fuses.

author: eblc1388
author_rank: Frequent Contributor
timestamp: August 06, 2023, 02:13:22 pm
content: Quote from: gotofbi on August 06, 2023, 06:24:03 amThe only way to get 24V(or 20V) is to connect the two power supplies in series. i.e. positive of one power supply to the negative of the other. However, there is one more twist as these are computer server power supplies. The negative output is solidly connected to the metal casing, meaning you simply can't connect them in series as normal bench supplies do. You will short out the first power supply if you do so, giving you an output of only 10V. You must modify the second power supply to remove the link between negative(-ve) and the metal casing, and then you can connect them in series to get 20V.I have prepared a drawing to show you why this is so. This operation is often referred to by others as "Floating the supply". If you search on YouTube, there are many videos detailing how to carry out the modification. As the modification is done while there is no ac power connected, it is pretty straight forward and safe to perform. Make sure you understand what to do before beginning the modification and remember you only need to modify one of the two power supplies.

author: Manul
author_rank: Super Contributor
timestamp: August 06, 2023, 07:01:06 pm
content: Not only that, but also powerful enough reverse voltage protection diodes must be connected in parallel with both PSU outputs. Two separate PSUs will likely not turn on at exactly same moment, so one of them will be momentarily backfeeded with reverse voltage. That can also happen if one PSU does not start at all for some reason. Output electrolytic capacitors work like (bad) diodes when reverse biased and might survive such abuse for some time protecting other circuitry, but this is very bad for them.

author: gotofbi
author_rank: Contributor
timestamp: August 07, 2023, 11:07:36 pm
content: Quote from: Manul on August 06, 2023, 07:01:06 pmI searched lots of serial connected server psu and non of people used reverse voltage protection diode between two psu.Do you have any suitable example?Quote from: eblc1388 on August 06, 2023, 02:13:22 pmYes you are right, I got bit confused and now I am back to my original planning which is 2x 1200W with output of 20V (10V each from PSU)Here is my final plan and please tell me if anything is wrong with the design.1. Using 6 AWG wires2. 3x AWG wire from PSU1 Positive to PSU2 Negative (my understanding is that this line can theatrically go up to 100A so using 3 of 60A rated wire)3. Using 2x QS8 connectors.4. Each QS8 connector will connect to 8 devices (total 16 devices since there are 2x QS8), and each device is rated 5A (100W with 20V)I made poor drawing with windows paint app. so please forgive me with poor quality hahaThank you so much!

author: eblc1388
author_rank: Frequent Contributor
timestamp: August 08, 2023, 05:55:11 am
content: Quote from: gotofbi on August 06, 2023, 06:24:03 amGotofbi contacted me by PM but as I can't include diagram in replies via PM, I chose to answer his questions here.1. Enabling the PSUMy prefer method is to use a 22K resistor to simulate attachment to server, and a switch or jumper to start the PSU. Please refer to the attached image for details.2. Reducing the output voltage.It is simply done using a 15K resistor, solder to the two designated position in the following diagram. Or if you have very good eyes and skill and prefer to use SMD resistor instead, you can just solder a 15K smd resistor on top of the "63B" resistor, the two connection points are exactly the same. This mod drops the output voltage to around 10V and allows minor output voltage adjustment from 9.7V to 10.3V.3. Undervoltage protectionIt is unlikely the undervoltage protection will activate for an output voltage of 10V. So unless this happens, nothing needs to be done in the meantime.4. Floating the power supply for series connectionOnly one PSU needs to be modified. I shall refer you to the following Youtube video by Joshua Bardwell. However, at time 11:00 in the video, he tried to insulate the case grounding on the AC side which is totally unnecessary and maybe unsafe. Remember you only need to take care of the two standoffs at the output side only. The material you'll need are two M3 nylon screws and two nylon or insulated washers.How To Build A 24v / 2400W Power Supply:

author: gotofbi
author_rank: Contributor
timestamp: August 08, 2023, 07:03:20 am
content: Quote from: eblc1388 on August 08, 2023, 05:55:11 amThank you so much for your help.Just ordered required parts and will give an update as soon as I work on this!

author: gotofbi
author_rank: Contributor
timestamp: September 07, 2023, 11:10:55 pm
content: Quote from: eblc1388 on August 08, 2023, 05:55:11 amTook long time to arrive than I expected but all the parts are here!I successfully soldered 330ohm and 15k ohm and PSU1 is successfully moded!I adjusted the dial as well and I nailed 10.0VOne question that I have is that, although I see 10.0V output, I do not see greenlight from the PSU.Is it ok to be like that? because I think I saw somewhere that it needs to be stayed on.Before I attach 15k ohm, I saw it stays green as well as the outputing 12vThanks!

author: gotofbi
author_rank: Contributor
timestamp: September 09, 2023, 10:24:53 am
content: UPDATEI successfully modded two PSUsPSU1, just 10v modPSU2, 10v mod with floating mod as wellChecked PSU2's chassis is not connected to PSU2's - padsPSU1's + to PSU2's -Powered each PSU one by oneChecked voltage from PSU1's - and PSU2's + and I only get 10vI was frustrated and disconnected everything.Turns out PSU2 is dead and not outputting any voltage but just spin the fan.Did I do something wrong? or were am I just unlucky and killed PSU2?

author: eblc1388
author_rank: Frequent Contributor
timestamp: September 09, 2023, 02:54:55 pm
content: Quote from: gotofbi on September 07, 2023, 11:10:55 pmWhat is the purpose of 330ohm and where does it connect to? I couldn't remember telling you anything about 330ohm.

author: eblc1388
author_rank: Frequent Contributor
timestamp: September 09, 2023, 03:27:23 pm
content: Quote from: gotofbi on September 09, 2023, 10:24:53 amAll the steps are correct. No problem so far.Quote from: gotofbi on September 09, 2023, 10:24:53 amStill no problem if there is no 20V loading connected to PSU1's - and PSU2's +. However, if full load is connected across them and you only power up single PSU, then there will be big problem. The unpowered PSU could be damaged because of reverse voltage produced by the powered PSU. This is exactly the scenario mentioned by Manul in the above post. Is the 20V load connected when you did the test?Quote from: gotofbi on September 09, 2023, 10:24:53 amLooks like PSU2 is now defective.You've mentioned the green LED not coming on. Does it happens on one or both PSU after 10V mod? As far as I remembered, the Green LED will light when AC mains is connected, with or without any 12V output. I couldn't check it for you as I'm away from home.Can any forum member confirm about the Green LED on these server power supplies?If you undo the PSU1 10V modification by de-soldering one end of the 15K resistor, and the Green LED lights up again, then we have to study the circuit more to see if its MCU actually detects low output voltage and disable the Green LED and modify that part of the circuit too.

author: gotofbi
author_rank: Contributor
timestamp: September 09, 2023, 09:19:58 pm
content: Quote from: eblc1388 on September 09, 2023, 02:54:55 pm330ohm is for pin 33-36 for PSU power. I know you suggested me better solution but I couldn't find all the parts so I used easy trickQuote from: eblc1388 on September 09, 2023, 03:27:23 pmYes I confirmed PSU2 is dead/defective.even after I remove 15K, I still dont see green light and no output voltage.PSU1 performs fine, 10v with 15k and no greenlight. Without 15k green light and 12.2v.From this video, around 16:50 tells about OVP and green light is related to OVP.Since im on under volt protection, I may still able to generate load but I dont know until my new PSU arrives haha.

author: eblc1388
author_rank: Frequent Contributor
timestamp: September 10, 2023, 12:19:58 am
content: Quote from: gotofbi on September 09, 2023, 09:19:58 pmOk. The PL-11 does include UVP "indication".Please refer to Reply#10 of the following thread:https://www.eevblog.com/forum/projects/hp-hstns-pl11-over-voltage-protection-voltage-increase/in which the OVP setting is increased. But in your case, you would need to reduce this OVP setting down so the resistor connection is a bit different, as shown in the following image. The 10K resistor value is a guess and you might need to increase/decrease its value. If you use a 50K variable resistor then you can starts from 50K and works your way down slowly until the green LED lights up. You then measure the correct value using DVM and fit a normal resistor instead. You would need to do this at the lowest desirable output voltage(e.g. 9.7V) and then you'll be fine at 10.0V.Addition: I search the web and found the PL11 voltage detection circuit with actual values, by a guy "LI Tao darwinbeing" at the following Github address:https://github.com/darwinbeing/HPServerPSUHack/blob/main/resources/PL11_OVP.pngWith this I can calculate the correct resistor value for you to try instead of using a 50K variable resistor. You can obtain asingle 16K resistoror a 15K+1K resistors in series for the modification.

author: eblc1388
author_rank: Frequent Contributor
timestamp: September 10, 2023, 12:55:53 am
content: To prevent back feed and reversed voltage condition from damaging your PSUs again, I would suggest you follow Manul's recommendation of adding protective diodes on the PSU outputs. I would suggest the use of a single phase bridge rectifier for simplicity of connection, plus you'll get double the current rating of the rated bridge rectifier. You do not need to use heatsink for the part but if you do mount it on a conductive surface, then you'll need to insulate the exposed flat metal part.Single phase bridge rectifier with voltage rating over 30V is OK but you should aim for the highest current available. If your full load current is say 80A, then find one with an average current rating of 40A because there is two diodes in parallel in a bridge rectifier if you connect them in the following manner.

author: gotofbi
author_rank: Contributor
timestamp: September 11, 2023, 08:48:04 am
content: Quote from: eblc1388 on September 10, 2023, 12:55:53 amThank you so much.I just ordered 16k ohm. it will take awhile to show up and since its just "indicator" I should be ok to use without it but will implement once it arrives.For Single phase bridge rectifier, I never used such thing so bit confused how I should implement.https://www.amazon.com/Baomain-Bridge-Rectifier-MDQ-200A-Module/dp/B08CN639BS/ref=sr_1_5?crid=2PR3BHZ3KVGHQ&keywords=single+phase+bridge+rectifier&qid=1694421505&sprefix=single+phase+bridge+rectifier+%2Caps%2C134&sr=8-5Im thinking about getting something like this but not sure its suitable.I attached revised design.Correct me if I made a mistakeThank you so much

author: MathWizard
author_rank: Super Contributor
timestamp: September 11, 2023, 04:14:18 pm
content: As for cables, computer ATX PSU's output really high currents, up to 12V anyways. They usually use a bundle of 16-18AWG wires. Some GPU's, will have 6 or 8x 18AWG input cables/plugs delivering 300-400W or more. That's 25-33A or more, at 12V, just for some comparison.

author: gotofbi
author_rank: Contributor
timestamp: September 11, 2023, 11:16:16 pm
content: Quote from: MathWizard on September 11, 2023, 04:14:18 pmThank you for giving valid point.I was so annoyed to use thick cables but I guess I could use 8-10AWG wires.

author: eblc1388
author_rank: Frequent Contributor
timestamp: September 13, 2023, 05:56:32 am
content: Quote from: gotofbi on September 11, 2023, 08:48:04 amThe MDQ-100A bridge rectifier from the same manufacturer is more than adequate and you really don't need to use the 200A version. Besides a brief startup moment, there is no current flow through the rectifier during normal operation.Your proposed connection is not correct. See attached for the wiring diagram for both the 100A and 200A parts.