Optimum Voltage from Panels

[slabman]

I am installing 8-100W panels and to minimize current through my #8 wires down to the controller, I plan on carrying the power down at 72 volts with about 11 amps. (4S4S2P) Any issues with a higher voltage like this?

[computerguy]

Voltage, no. Well, not really. 72 volts can do a human some damage. Be careful. The problem I see is you need to be careful with shading on the panels. Shade any of the 4 just a little and you'll lose a lot of charging capability.

[Jon_C]

Not an issue as long as your solar controller can handle that voltage.

Im running 3 100 watt panels in series getting around 60 volts, my Victron controller can handle up to 100 volts from panels

[slabman]

Sorry, I should have mentioned my controller is a Victron 100/50, so no issues with max voltage here. Just wonder about any other considerations here. Concerned with line loss (#8 wire) and over-current in the MP-4 fittings.

[Jon_C]

Originally Posted by slabman

Sorry, I should have mentioned my controller is a Victron 100/50, so no issues with max voltage here. Just wonder about any other considerations here. Concerned with line loss (#8 wire) and over-current in the MP-4 fittings.

MC4 connectors are rated at 20 amps so there should be no issues if your max current is 11 amps.

Connecting panels in series is best for keeping current low and minimize line losses.

I think your good with #8 wire, my buddy and I recently put 800 watts with 10 gauge no issues, we used series / parallel to keep amperage within spec of the wiring.

[Pappion]

Originally Posted by slabman

I am installing 8-100W panels and to minimize current through my #8 wires down to the controller, I plan on carrying the power down at 72 volts with about 11 amps. (4S4S2P) Any issues with a higher voltage like this?

DC sustains arcs, while AC goes thru 0 volts and may extinguish arcs.
Use DC rated switches, circuit breakers, and fuses, for the voltage.

BTW: there are MC4 style fuse holders.


Most MC4 and solar wires are #10 gauge. Make sure your MC4 can crimp on the #8. Don't buy cheap, make sure product claims MC4, not just solar connector. I had issues with BougeRV.


Shading will cause a section of the panel to drop out. Current is routed around it thru Bypass diodes (in panels connector box). The string voltage will drop. So one string could be higher voltage than the other. No telling if your MPPT controller will harvest from both strings, just too many variables with shading. Some people use a MPPT controller for each string.
BTW: If there are 3 or more strings in parallel, then each string should be fused.