I have an external SATA hard drive enclosure that has its own power input. I would like to be able to run a Raspberry Pi from the same power input.
The enclosure takes a 12VDC input (currently I'm using a 1.5A power supply but I'm sure I have a 2A one lying around somewhere) and converts it to a SATA power input for the drive. The hard drive says it wants 0.65A from the 5V on the SATA power, and the RPi draws 1A from its 5V input at most. The intended setup is for a small NAS so the Pi will be using its ethernet port on the usb hub chip but no peripherals after the original setup (which can be done when powered normally).
So, is it possible/sensible to split the 5V cable on the SATA power and hook it up to a µUSB to power the Pi, bearing in mind the variable power consumption of the drive and Pi?
If not, why?