Good deal. Sounds like you now have comm with it.
Convert the two values to an integer with something like this.
int Readspanning2 = SPI.transfer(0x01);
int Readspanning3 = SPI.transfer(0x01);
// shift the hi byte to the high byte
Readspanning2 = Readspanning2 << 8;
// clear the hi byte of the low byte
Readspanning3 = Readspanning3 & 0xff;
// put them together
int RSint = Readspanning2 | Readspanning3;
edit. Sorry. My bad. In my hurry, I reversed the bitwise operators. They are correct now.
BTW, thanks for the info on that MPPT charger. I use solar power frequently. That could prove to be a very useful tool. I mean, in some cases, why re-invent the wheel?