I honestly didn't think to ask that question. I got my unit second hand so I'm not sure if it's covered in the first place, but it's certainly a fair question to ask RBT before you try it.
That said, you aren't modifying the device itself, you're just using a different power source than the included battery.
That said, you aren't modifying the device itself, you're just using a different power source than the included battery.