APC Back-UPS XS 1300 LCD with ReadyNAS Pro 2

SuperNASman wrote:
Since there is nothing special about the cable, do you have any idea why the RJ-45 to USB adapter isn't working?

Yes. RJ45 is incompatible with USB in every way, so an RJ45-to-USB adapter contains a microcontroller and plenty of circuitry to perform the translation between the two.

Your UPS, though, doesn't speak RJ45. It speaks standard USB with only one difference from other USB devices: Instead of a standard USB socket, it has an RJ45 socket. In other words, the signals on the wire are no different from USB; it's just the shape of the connector at the end of the wire that's different. You don't need or want a USB-to-RJ45 adapter; that adapter will do too much. What you need is simply a USB cable with the device-side plug cut off and replaced with an RJ45 plug.

You can pay $35 to APC for their cable or you can buy one from a third party (like Amazon) for less than half that price. Or you can make your own; wiring diagrams are on the web. If you buy a third-party cable, make sure you're buying one with an 8-pin RJ45 connector; APC later switched to 10-pin RJ50 connectors.