The vRef setting depends on the value of the current sensing resistor on the driver. Some Pololus use a 0.05 ohm resistor, and others (Stepstick) have a 0.2 ohm resistor. This means you cannot always go by the vRef setting someone else is using.
My Kossel Mini uses a Printrboard with A4988 Pololu Stepstick drivers.
I have my vRef set to 1.65v. This comes out to just under 1A of current per stepper.
Explanation and formula here:
Pololu drivers current limit configuration
I have experimented with this setting, and found that heat quickly becomes an issue for both the motor and the driver with settings much higher than 1A. The steppers were actually hot enough to warp the PLA motor mounts on my printer.
Ok, so If we assume a current of about 1A per stepper. The highest power PoE injector/tap I’ve seen are about 30w or (2.5a @ 12v) This isn’t leaving us much room to run the other electronics.
I’m thinking about the possibility of running the tracker from battery power, but using PoE to keep the battery charged.