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Powering a backplane with 850W 80 Plus

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jhyler
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2024/01/24 10:46:19 (permalink)
I need to power the backplane in my Norco RPC-4220 case.  The backplane is made up of five rows.  Each row has a single 4-pin Molex connector which powers the four disks in that row.
 
The obvious way to do it is to use SATA-to-Molex adapters and use the SATA cables to power the backplane. Since there are three SATA cables with three connectors each, two of those cables would be connected to two rows each, i.e those two cables powering 8 drives each, with the third powering a single row.
 
The alternative is to use the PERIF cable to power four of the rows - 16 disks on that one cable - and one of the SATA cables to power the fifth row.  If I do this then I'll end up using a SATA cable with SATA-to-Molex adapters to power a couple of fans.
 
What I'm basically saying is I'm not sure how much power is available through the SATA cables compared with the Molex/PERIF cable. Which of these is the better choice?
post edited by jhyler - 2024/01/24 10:47:44
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    ty_ger07
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    Re: Powering a backplane with 850W 80 Plus 2024/01/27 07:27:24 (permalink)
    It really depends on the power supply and the size and rating if the wires it uses, so I won't give you exact numbers.  But, in general, use the 4-pin molex connectors as much as you can, because they can safely provide about twice as much power than SATA connectors.  Sometimes way more than twice, sometimes less than twice, but more either way.

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    jhyler
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    Re: Powering a backplane with 850W 80 Plus 2024/01/27 10:21:00 (permalink)
    Thanks, I appreciate the reply.  The power supply is an EVGA 850w G7.  The power supply Molex and SATA cables all look like 16 gauge wire to me.  The SATA-to-Molex adapters use 18 gauge wire.
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    vcbb10
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    Re: Powering a backplane with 850W 80 Plus 2024/01/27 10:50:54 (permalink)
    The issue with using SATA to convert to molex and potentially power 4 drives is likely in the SATA connector to the molex adapter.  Like ty_geer07 mentioned, the SATA connector is not rated for the same power as molex.  When you try to run a backplane with multiple drives, you have more power draw.
     
    Will it work?  Probably.  It also depends on the drives you connect on the backplane.  Spinning high RPM SATA/SAS drives may not be a good idea.  Molex is a better idea when possible, though.
     
    I think SATA is rated for around 50w for 12v.  Molex around 130w.  3.5" drives are normally 5-10w or so (max is higher).  High RPM and especially high RPM SAS can be higher.

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    jhyler
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    Re: Powering a backplane with 850W 80 Plus 2024/01/27 11:52:34 (permalink)
    I appreciate the help, folks.  Based on your input, I think this is my plan.  First, I'll contact customer support and see if they can sell me a second PERIF cable, assuming it can be plugged into a power supply connector labeled SATA. (They have a 3x Molex cable listed for sale, but the listed Supernova compatibility only goes up to G6.  I have a G7, and the cable they included with mine is a 4X Molex cable.  I bet that cable will work, but I want them to tell me so.)
     
    In the meantiime, I will use the PERIF cable they included to power four of the five rows.  One of my rows currently only contains three drives.  I will check my parts box to see if I have a Molex splitter, and if I do I'll use it to power the fifth row.  If not, I'll use one of the supplied SATA cables exclusively for the fifth row via a Molex converter.  I'll then use a second SATA cable with a Molex converter to power a couple of fans.
     
    Sound reasonable?
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    NordicJedi
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    Re: Powering a backplane with 850W 80 Plus 2024/01/27 16:41:23 (permalink)
    Yes, you can use the Molex or Perif cables in the SATA ports on the power supply for the G7's.  Customer Support would be a great way to go to see if they have any spare cables, given that the store no longer sells them.  G7's are also compatible with the G2/G3/G5/G6/GP/GA/GT/XC/FTW (and their respective Platinum and Titanium models) Molex and SATA cable series.  The preference is definitely to use the molex cables over SATA for powering multiple objects, even if decent or better quality splitters are used.  No disagreement with others on this.
     
    If looking for them separately, on a place such as Cable Mods, you would look for cables that are compatible with the G2/P2/T2 power supplies like these:
    https://store.cablemod.com/products/?filter_series=e-series.

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