Solar - more cells = better?

[noelex 77]

Originally Posted by hpeer

Thanks for that.

Question, I assume that’s true for a clear day with good sun. What about on an over cast day? So am I getting 40% of whatever is available or 40% of max?

In overcast conditions the solar output will be less, but the percentage gain from voltage conversion will remains very similar.

This is becase with reduced illumination solar panels produce much less current, but the voltage is only slightly reduced. In overcast conditions the charging battery voltage is likely to also be slightly lower so the voltage mismatch that is producing your loss in output will remain almost the same.

A couple of points:
1. The figure of 40% is a ballpark number based on the mismatch between your solar panel voltage (Vmp of 30v ) and your battery voltage. With lower voltage, so called “12v panels” that have a Vmp of arround 17.5v, the gains from the voltage conversion inherent in MPPT controllers will be much less. Likewise, if you used my 60v panels without a MPPT controller the loss would be much greater.
2. I am talking about available output. If you batteries are full and solar panels are producing enough power to cover your loads then improving the available output will not do anything. The extra potential power cannot be used, so the available output will just be reduced by the regulator.

Edit: I wrote the above before your post #45:

Originally Posted by hpeer

Wrote a long reply restating the question and answered it myself. Current out put is limited to 8 amps at whatever voltage up to Vmpp. That’s at full radiance. Reduced radiance reduces amperage available, but voltage remains the same.

So yeah, I basically get nothing from 1/2 my panels. No mitigating circumstances.

MPPT would raise voltage coming from panels while still provinding 8 amps, more power. Got it.

Yep. A great summary

[hpeer]

And thank you for that clafcation. It’s making more sense now.

It was an esoteric point not covered by anything I read on the web.