If you use Google you will se that a standars wireless minipci card use up to 500mA in Tx (standard means about 18dBm) so if you use 3xminipci=1.5A nedded + the routerboard (I think 500mA) = 2A !!!
But as I remember your card has 400mW and it consumes 1.5A per card so do the math.And is better to use 18-24v adapters.
I’m starting to belive that google is for smart people…