I am about to re-pin some PSU cables and want to make sure I clarify some technical questions before I proceed. I would appreciate some feedback and confirmations.
Using this above picture of MOLEX connector for reference and land-marking;
Pinout
Other general questions:#1 What backplane ports are powered by each J-port?
#2 Can the PDU handle 15 drives with a single PSU cable to 4x Molex?
#3 If a PSU>PDU cable with 4x Molex is used, where should the first Molex go? J1>J2>J3>J4, J4>J3>J2>J1, or alternate order?
#4 Can the PDU handle 15 drives with 2x PSU cables to 2x Molex?
#5 If 2x PSU>PDU cable with 2x Molex are used, where should the first Molex go? J1>J2;J4>J3, J2>J1;J3>J4, or alternate order?
#6 What cable gauge is recommended for PSU>PDU cables?
Thank you!
I think your markup is correct. My spatial orientation may be off, but I think the “Front View” in the internet image is wrong.
The backplane draws power across all the molex connectors that are plugged in. See
Does each of the four Molex connectors on the power distribution board power a subset of the backplane, or do all the Molex inputs get combined to feed all the drive and fan output draw?
IE, is it something like;
J1 - bays 1-1 to 1-4
J2 - bays 1-5 to 1-8
J3 - bays 1-9 to 1-12
J4 - bays 1-13 to 1-15 and fans?
The reason I’m asking is, assuming a fully loaded unit with 15 drives of the same model, will one Molex tend to draw less power and be a better candidate to daisy chain power for anoth…
This is all discussed in Molex Clarification . The TL;DR seems to be that the potential issue is not the PDU, but the spec for the amp draw across a single molex connector. A single PSU to 4x molex puts you at or over that. You are better to spread the load over at least two PSU ports.
ZVeguillaCotto:
#3 If a PSU>PDU cable with 4x Molex is used, where should the first Molex go? J1>J2>J3>J4, J4>J3>J2>J1, or alternate order?
Doesn’t matter, see #1 .
This would be the preferred minimum setup. See #2 .
ZVeguillaCotto:
#5 If 2x PSU>PDU cable with 2x Molex are used, where should the first Molex go? J1>J2;J4>J3, J2>J1;J3>J4, or alternate order?
Doesn’t matter, see #1 .
16 AWG I think.
2 Likes
I agree parts of it looked wrong. I think it was showing the Molex end on one side and a Molex extension on the other.
I have edited the post with clearer images and labels to better inform future readers.
Thanks for the answers. I will go for 2x PSU to 2x Molex cables and report back.
Thank you @DigitalGarden for answering all of @ZVeguillaCotto questions. You rock!
All of your answers are correct and provide reference material to other posts on the forum so thank you for that.
45Drives HomeLab Power Midplane Rev 00.B
