How do I properly power a backplane with 3 molex connectors using an ATX PSU?

[philfromqueens]

I recently bought a 12x 3.5" hdd supermicro backplane that has 3 molex connections on the back that I was planning on powering with one of the two ATX PSUs I have laying around.

I assumed I could use a molex cable with 3x molex connectors on it to power the backplane but it turns out neither PSU has such a cable and they dont even have a molex cable with 2 molex connectors on it. Even if I were to get such a cable from the manufacturer would it be advisable to connect the backplane to one string of 3 molex connectors?

The PSUs I have do have cables with some sata connectors and one molex on the end. Could I possibly use a sata to molex adapter in order to populate all 3 backplane molex connectors with one cable? I assume this isn't advisable because sata connectors are only rated for like 50w whereas molex connectors are rated for much more.

Whats the proper way to power such a backplane with an ATX PSU? I was hoping to power two such backplanes with one psu since the wattage drawn by 24 drives should be easily handled by the either of the 650w or 750w psus I have.

If it helps, I have a BPN-SAS3-826EL1.

 

[RageBone]

my own reasoning for a 8 drive dual molex backplane was that i only have one strand with two molex and the OEM would not have two Molex on the strand if the cable couldn't take it.
Its in direct airflow and the plugs should be able to take it anyway so i populated only one of em.

Nothing gets hot so far.