Originally Posted by bluegreen
Not some random connector. The wires from the pannel itself are not very big. My 30 volt 9 amp panels
are in series. So i have 66.7 volts of pannel with rather small wire from them to the controller. At that point it goes to 24 volt system where i run the heavier guage to the batteries. In all the research
ive done, the wire size seemed to be the very least of all the powerloss problems ive ran into. And if i want to add more pannels in series it dosent affect the current
on the pannel side. Same amps just volts increase. The controller does the rest. So traveler having roughly the same pannels with a mppt
controller swapping 60v 9a to 12v 50a, his controlers efficiency is far more critical then the pannel wire size. Thats all im saying. The 1.5 volts lost
will only account for 10 watts on either side. Having a small shadow pass over the pannels will effect it more then that. Its just how i see it. Electronics
is a lot more rough n dirty then i would have thought prior going to electronics
engineeringin college back in 1998. Its getting foggy for sure so i like reading this thread and voice an opinion when i can.
Maybe i will try heavier wire and see if it makes any difference. I however believe the batteries internal resistance make the bigger difference. But let me know how this works out. Im interested for sure. And good luck to all.
In your situation, since you have your panels
wired in series you have a higher voltage and lower current
(than the parallel case). (As you noted above.) And yes, you can add panels in series, using the same wire, without increased loss as long as the controller can handle the voltage.
In the OP's case there were two "30V" panels, with independent wiring
to two MPPT
controllers. Do the math -- there will be a 5% loss with the #14 wires, but a 2% loss with #10.
As for shadows, etc., being a bigger problem than wire loss, that may be, but that's still no reason to throw away power. We advocate using MPPT controllers because they give us a 5 or 10% gain (and for other good reasons).
At the end of the day, we are arguing about finding the point of diminishing returns when choosing wire gauge. Neither of us would use #18 wire for this 30-ft run, even though it could carry the current without getting too hot. I say that #10 gives a 2% voltage drop and so it the smallest I would prefer to use.
I also am saying that the connector size should not determine the wire gauge. If the connector is too small for the proper wire then an adaptor of some sort is called for.