There are 3 different boards by Yihi with the SX330 label. V1 is low wattage v2 is 50 watt and both are 3.4 nominal input voltage. The V3 is 100 watts, higher with software update, but it requires 6.8 nominal, stacked/series,
batteries.
As far as I know Yihi thinks all of them are for manufacturers and not modders. I know of no place to get just the board.
I like the SX350, up to 60 watts with new wires and batteries in parallel if you want.