Jules_Theone
Member
I've recently moved house, finally got round to tinkering with the solar panels and grid tie inverters today, haven't got all the kit yet but started putting things together to test.
I have 2x 235W panels, 1x 40W panel and 1x 80W panel, 2x 350W (Chinese) GTIs. Will buy isolation switches, electric meter, circuit breakers etc to do it properly later.
My problem is that the GTIs are designed for 14V to 28V which worked perfectly for the 80W and 40W panels but I measured the open circuit voltage from the 235W panels and they were putting out around 34V which means the GTIs don't start. It sort of works if I cover part of the panel so the voltage comes down then the GTI loads the panel and it continues to work when I uncover it. I tried connecting the GTI to 2/3 of the panel but that would mean it would not use the whole panel. Also tried putting 6 diodes in series with the panel to bring the voltage down but with little current flowing (40mA) the voltage doesn't actually come down much.
I had some ideas about putting a small load on the panels to bring the voltage down to 28V but haven't tried it yet and think it would probably be a waste of power, alternatively, I thought to add a voltage clamp sort of thing like a FET and zener diode to trim the voltage and so would stop conducting when the GTI is loading the panel (bringing the voltage down) which seems better than a resistive load. It's gone dark now so I'll experiment again tomorrow, hopefully it'll be sunny... One last thought I had was that it seemed the problem was that the GTI refused to draw (much) current because the voltage was too high so if I can get the GTI to load the panel(s), the OC voltage would drop and it would work. I connected a 235W and 80W panel in parallel and it seemed to work, but that might have been that I connected the 80W THEN the 235W.
Are any of the above ideas any good or does anyone have better ideas.
Thanks,
Jules.
I have 2x 235W panels, 1x 40W panel and 1x 80W panel, 2x 350W (Chinese) GTIs. Will buy isolation switches, electric meter, circuit breakers etc to do it properly later.
My problem is that the GTIs are designed for 14V to 28V which worked perfectly for the 80W and 40W panels but I measured the open circuit voltage from the 235W panels and they were putting out around 34V which means the GTIs don't start. It sort of works if I cover part of the panel so the voltage comes down then the GTI loads the panel and it continues to work when I uncover it. I tried connecting the GTI to 2/3 of the panel but that would mean it would not use the whole panel. Also tried putting 6 diodes in series with the panel to bring the voltage down but with little current flowing (40mA) the voltage doesn't actually come down much.
I had some ideas about putting a small load on the panels to bring the voltage down to 28V but haven't tried it yet and think it would probably be a waste of power, alternatively, I thought to add a voltage clamp sort of thing like a FET and zener diode to trim the voltage and so would stop conducting when the GTI is loading the panel (bringing the voltage down) which seems better than a resistive load. It's gone dark now so I'll experiment again tomorrow, hopefully it'll be sunny... One last thought I had was that it seemed the problem was that the GTI refused to draw (much) current because the voltage was too high so if I can get the GTI to load the panel(s), the OC voltage would drop and it would work. I connected a 235W and 80W panel in parallel and it seemed to work, but that might have been that I connected the 80W THEN the 235W.
Are any of the above ideas any good or does anyone have better ideas.
Thanks,
Jules.