Very long run; high voltage required

[mailseth]

Hi all! First time poster here. I'm considering a site for solar panels in a clearing ~350' away from my cabin. I understand that this would require a high voltage to efficiently carry power over that distance. So the Classic 250 charge controller is what I'm looking for.

But looking at the calculator, the voltage at 6 panels in series puts me up over 250 volts unless it's above 32F. This is acceptable half the year, but the other half it tends to be below freezing most of the day (with 0-10' of snow on the ground.) I was wondering if there's a good way to nudge the line voltage down a few volts, such as by adding a small heating coil in the wire run to the panels? (Is that compatible with the charge controller?)

[FNG]

Lets look at this, 350ft isnt that far. Making a couple assumptions here but lets run the numbers:

48v battery
12 60 cell modules

If we go 3 in series and 4 strings we get around 90v and 36 amps so 1/0 aluminum gets us to about 4% vd
If we go 6 in series and 2 strings we have 180v and 18 amps so #6 aluminum gets us to 4%

1/0 al is about 75 cents a foot compared to 29 cents a foot for 6 gauge so not counting the ground you would have an upcharge of $322 for the wire, Considering the upcharge of a classic 250 (or a 600v from a competitor) and the up charge for breakers etc I think its cheaper to go low voltage and all controllers will operate more efficiently when closer to battery bank voltage

[mailseth]

I was looking at the same numbers, but then I read this in the manual:

If this sounds too complicated use this rule of thumb in selecting the proper Classic. PV runs up to 100 feet, use the Classic 150, runs up to 180 feet, use the Classic 200, or above 180 feet use the Classic 250.

I’m also considering running a number of wires once I have the trench dug so I can later expand and increase the size of the array by adding another controller. (Or add a micro-hydro). So heavy gauge wire might end up getting expensive. On the plus side, the multiple wires will share the load in the short term.

[australsolarier]

or spent the money on  more solar panels

[mike90045]

I have a 980 foot run to my pump.   was considering a 2nd system but ended running about #2 alum wire. Bought 3 1,000 foot spools, had 4 pull stations and 4 helpers pulling,  and squirting cable lube into the conduit.  Use the good anti-ox goop and AL rated connectors.  Working good for 8+ years now.

The cold voltage is from the panels, not a correction at the CC, heaters won't cure the high cold voltage from the PV array at dawn.  You have to select a controller that can handle the sunrise voltage.

Don't mix DC wires in the same conduit as AC, put another conduit in for AC.   And a spare conduit if you ever think you want ethernet or data cable.  I've got one dedicated to the pump float switch in the tank.  3 conduits in my trench.

[australsolarier]

best thread in two ethernet cables right away. a 300m roll is very cheap

[mailseth]

I have a 980 foot run to my pump.   was considering a 2nd system but ended running about #2 alum wire. Bought 3 1,000 foot spools, had 4 pull stations and 4 helpers pulling,  and squirting cable lube into the conduit.  Use the good anti-ox goop and AL rated connectors.  Working good for 8+ years now.

The cold voltage is from the panels, not a correction at the CC, heaters won't cure the high cold voltage from the PV array at dawn.  You have to select a controller that can handle the sunrise voltage.

Don't mix DC wires in the same conduit as AC, put another conduit in for AC.   And a spare conduit if you ever think you want ethernet or data cable.  I've got one dedicated to the pump float switch in the tank.  3 conduits in my trench.

Yeah, I realize now that the dawn high voltage (Voc) is low amperage and therefore no voltage sag. So a resistance isn’t going to work to drop the voltage when I need it lower.

Is it necessary to run so much conduit if I’m purchasing direct burial wire? Is it a matter of likelihood of replacement due to damage? I know it would be important to separate the AC and the Data cables due to induced current, but are there other reasons to separate them?
https://www.wireandcableyourway.com/underground-secondary-distribution-cable/

I’m thinking of running the cables along a large 6” pipe in the trench for the possible micro hydro in the future. This is all in an area that is marshy and flooded for much of the year.