I bought two used Tigo TS4-O Optimizers and tried putting them on two panels (370W) for testing. I've never used Tigo optimizers before but what I've read is that by default, I should be reading the full panel voltage (40V) at the optimizer output leads. But I'm reading only 7mV on one optimizer, and 0V on the other. I was hoping that these will "just work" with a panel without buying anything else, per this doc.
Any ideas?
Any ideas?