I am looking for a solution to individually dim (or if not possible switch) 30 Cree XR-E LEDs driven by a 18v 4.0mAh Makita battery and a step-down converter to go from 18v to 3,5v capable of handling about 120watts (total power when all LEDs are lit).

I'm thinking of using a Raspberry Pi 3, combined with a FadeCandy controller and a set of WS2811 drivers. Would this work? And how can I use the WS2811 chips to control high-power LEDs?