Switchable s/p panel arrangement

[Red0ne]

Maybe the danger zone is too much for this, but I think I didn't saw any mentions of this yet.
So we have a truck mounted system of limited space, implying it would be worthwhile to go with maximum efficiency big panels that also happen to have ridiculously high Voc. Then comes an SCC of quite limited voltage. What if... the array was connected to a switch that would make it parallel during the high sun, but went to series connection for mornings/evenings/otherwise poor light conditions? Let's say some voltage limiting device prevents the SCC damage in case of sudden voltage surge in series mode, and there is a motorised switch to take care of make the changes in optimal conditions? Is it worthwhile at all or the idea is unheard of simply because it does not make sense?

 

[MichaelK]

That's really not going to work. Panels normally produce almost the same voltage from rather dim light, up to full direct sunlight. What really changes dramatically is the amperage output. In dim light amperage will be close to zero. In bright, direct light, it will be close to maximum. Voltage will gradually change as the panel temperature changes, with voltage going up in cool conditions.

So, having panels with a high Voc that is likely to fry the controller will happen just as likely in dim, shady conditions, as in bright sunlight. But, working with real numbers is better than just generalities. What is the Voc of your panels, and what is the maximal voltage your controller can handle? What's the lowest winter temperature you'd expect these panels to ever be exposed to?

Since you're installing this on a truck roof, I'm assuming that your wiring distances are not going to be that great. Depending on your panel specs, you might just leave them permanently parallel, and not worry about it? What are the numbers?

BTW, Mr Murphy will come looking for you if you tried setting up something that requires manual switching for system protection.

 

[Red0ne]

That's really not going to work. Panels normally produce almost the same voltage from rather dim light, up to full direct sunlight. What really changes dramatically is the amperage output. In dim light amperage will be close to zero. In bright, direct light, it will be close to maximum. Voltage will gradually change as the panel temperature changes, with voltage going up in cool conditions.

I think I've heard that, but got very stuck with the circulated idea that series connection is beneficial for low light. Thanks, that makes quite some sense.

So, having panels with a high Voc that is likely to fry the controller will happen just as likely in dim, shady conditions, as in bright sunlight. But, working with real numbers is better than just generalities. What is the Voc of your panels, and what is the maximal voltage your controller can handle? What's the lowest winter temperature you'd expect these panels to ever be exposed to?

I didn't decide/purchase the panels yet, but I was thinking about getting two or three 72 cells panels in 450W magnitude, those come with Vocs about 50V and I have a controller that will only handle 100V. I guess with three I'd not be worried because I'd be overpaneled anyway, but getting only two and switching them around to get more juice started going round my brain.

Since you're installing this on a truck roof, I'm assuming that your wiring distances are not going to be that great. Depending on your panel specs, you might just leave them permanently parallel, and not worry about it? What are the numbers?

That was my first idea, and I definitely will

BTW, Mr Murphy will come looking for you if you tried setting up something that requires manual switching for system protection.

Hence my last lines, the process would be automated and having some additional means of protection too. Thanks for the reality check anyway