Trying to figure out why my motor cooling fan rpms fluctuate a lot when giving throttle. In fact, the fan almost stops when I give it full throttle. This happens on both direct to battery connection on esc and from RX(less powerful, but the fluctuation is not that bad). Wondering if it is cooling it enough or just robbing voltage. How do you guys connect your fans?

Sounds like your fan is a 12v fan, the voltage drop is causing the fluctuation.