i would direct solder them to the pos & neg of the esc, that way you know the fans are getting there power directly from the battery. if you want to keep soldering to a minimal, just solder 1 pair to esc then use a y-harness to allow both fans be used. I use 2 x 5v fans, 40mm fan mounted on my upper fram directing air to the top of motor, then i have a 25mm fan mounted on my mamba max's heatsink, both direct soldered to the pos & neg batt tabs of the esc...