Ok, folks...hope you can help. I've built 2 PV panels from ebay cells. 1 is mono, the other is poly. Both panels appx 196W. (49 6x6 8A 1/2V cells in series...7 strings of 7 cells) At max. output, I'll get 24.5VDC @ 8A from each. My GTI turns on @ 14 VDC, & it's max input is 28VDC. (300w constant, 600w peak rating).In low light, I'm not making enough voltage to turn on my GTI (both panels are hooked to the GTI in parallel) What I'd LIKE to do is find a switch or relay that will automatically switch my panels to series when light is low (dawn, dusk, cloudy day, etc.), & then back to parallel when the voltage rises enough to keep the GTI on line. Somebody told me that he thought a solid-state charge controller could do this, but he wasn't 100% sure. Thanks in advance....Doug