Forgive my English
I just want to add my 2 pennies to the lot... I have come across the same problem. I though this was an isolated instance, so I tough of tracing the pin outs of the cable and measuring the power. But I have 2 powered esata ports, why would both fail to work. But again. All hdd'sare designed to take a certain amount of power 2.5" Hdd are not allowed to draw more tha 500mA therfore 120Gb,250Gb,320Gb,500Gb,1Tb etc would use the same maximum current alowed. The bigger capacity drives do not use more power. There is no such thing as over powering, unless you fail to use the 5V and use teh 12V instead then you will burn the drive. That is why they make things idiot proof.
To get back to my point. the interface cable is quite simple. its has a few requirements to get it to work.
1. POWER
2. DATA Inteface
3. Screening
1. Power
12V is normally used to power the drive(not used in this case)
0V(GRND)
5V is used for DATA and this case to power the drive aswel.
0V(GRND)
2 Data interface
5V used for the interface signals
0v (GRND)
| 1 | GND | Ground |
| 2 | A+ | Transmit+ |
| 3 | A- | Transmit- |
| 4 | GND | Ground |
| 5 | B- | Receive- |
| 6 | B+ | Receive+ |
| 7 | GND | Ground |
3. Screening.
To protect data transmissions from external interference and the drives.
My conclusion
Esata is one SATA port with power to connect ot external drives, therefore it must work. The power comes from the motherboard or if you dont have onboard esata from the power supply, and a SATA port on the motherboard is used for the interface. It should be a direct link. In theory you should be able to trace each pin, but there could be protective electronics inside that may prohibit such an effort.
I do not want to enrage people but the cable should be straight forward. no silly electronics. When you plug in your esata drive, the light should come on( not in my case I think its faulty). Then in your windows device manager you should scan for hardware changes, that should do the trick if not return the cable. Linux users I just use my disk utility if it does not show its not connected.
Thanks for reading.. 
... so apparently I'm one of the lucky ones 
Like others the USB 2.0 adapter/cable works fine ... but for a 1TB external drive, that's not fast enough. So I spend the extra money on the eSATA adapter/cable.
Win 7 recognizes the drive fine, but Seagate Manager software does not recognize the 1TB drive via the eSATA cable.
I've used Seagate Manager successfully for at least a year with an older 320 GB Freeagent Go drive, and SMgr recognizes the 1TB drive on the USB 2.0 cable.
What gives?
Can anyone confirm whether SMgr should be able to backup to a 1TB eSATA GoFlex ultraportable?
Makes no sense that it doesn't
Related post:
Seagate-Manager-does-not-detect-GoFlex-drive-with-
