Can I connect a 2.5" together with 3.5" on the same power cable?

Solution
You will have no issues.

You can put a 2.5 HDD, 2.5 SSD, 3.5 HDD, and 5.25 dvd drive on the same set of 4 connectors and it will work just fine. There is no load issue of putting all of them on the same cable. The 12v on one sata cable is on the same rail as the 12v on the other cable anyways.
You should be able to. I have a Seagate 2TB and Samsung 850 EVO on the same cord.

I"m using an Antec Earthwatts Green 650.

I imagine that the worse case scenario is just that one doesn't turn on. I highly doubt any harm would come if it doesn't work (99% chance it will work though)
 
Yes.
A SATA power cable provides 3 voltages 12v, 5v 3.3v, these voltages run over different wires and different corresponding pins on the connector, your 3.5" drive will pull from the 12v, while the 2.5" drive will pull from the 5v wiring.
In fact many 3.5" drives can pull from 12v and 5v.
 
You will have no issues.

You can put a 2.5 HDD, 2.5 SSD, 3.5 HDD, and 5.25 dvd drive on the same set of 4 connectors and it will work just fine. There is no load issue of putting all of them on the same cable. The 12v on one sata cable is on the same rail as the 12v on the other cable anyways.
 
Solution