Thanks for the replies, Guys. I must confess to an error, however. I thought the Surface Pro was plugged in, but someone had swapped the plug out at the wall, so it actually wasn't. When I plugged it in, the Surface Pro did start seeing the drive.
So my experience is exactly like that of the OP, where it doesn't run without being plugged into power.
This dramatically reduces the value of the Surface Pro to me. These aren't large desktop external drives, these are low-power notebook drives. The enclosures don't even have ports for an external power supply because no modern computer should need them. They
both run with no external power on my desktop and laptop. I am rather baffled that any designer would make a conscious decision to cripple the Surface Pro in this way. It's a portable device with limited local storage. If we were to ask people to list the
top 5 things they'd want to do with such a device, attaching a small portable external drive would probably be in everyone's list.
I was examining this as a potential device for my college to buy more of, but this isn't turning out to look very promising. This is about the fourth big thing that has gone wrong since I started using it (not knowing whether the touch keyboard is attached,
regularly locking into the wrong orientation, the touch keyboard going bad, the schizophrenic Windows 8 interface, and now we can't actually use the USB port for the main thing it's made for). I guess that's five things, but I knew about the interface before
we started, so only four are a surprise. I guess this is what Apple fans mean when they talk about 'it just works', because this doesn't. I also evaluated the iPad and, while there are lots of things I wish it did differently (or at all), what it does do,
it does reliably. My time with the iPad was focused on exploring it's capabilities. My time with this Surface Pro has been characterized by hours spent troubleshooting things that don't work right.
Sorry for the rant, but being able to access portable hard drives in the field was important and it's probably the last straw for this evaluation. I'm really disappointed because I'm a Windows guy and I had high hopes for the Surface Pro.
There is not enough battery capacity to run the Pro AND a device that requires/uses substantial current. Even an iPad doesn't supply this 'magically abundant' current.
So... get yourself a portable battery/solar/fossel fuel powered 'powerpack' for these ventures where no Ext. AC is available for an HDD. OR.... 1) use an SSD drive (uses 1/4 the power of an HDD) or, 2) use the microsd slot, with 64G cards, as it is intended.