Solar wire size & amps question

[hdossett]

I currently have 300 watts of solar and want to double that.

Current system is 4x 75 watt 12V nominal (17v output)

What I would like to do is replace those units with 4x 130 or 4x 150 watt.

Question is "What amperage do I use to calculate the wire size needed for a 20 to 25 foot one way run?"


The 130 watt panel I am looking at is 130 Watt, 6.55 Imp, 19.80 Vmp.
I figure the max Volts for charging will be 14V. That would 130/14 = 9.3A

Do this times 4 and the amps would be 26.2A, or 37.2A

26.2A, 25' run 6 gauge wire = V drop of .532 (4.4%)
37.2A, 25' run 6 gauge wire = V drop of .75 (6.3%)

So... Which numbers do I use? (I may go with a 24v panels (36.00Vmp))


Harold

["007"]

Check this site out has a wire calculator for your wire sizes to match solar panels.

[Spikester]

There are much more efficient/effective panels/systems available, check this site out, they have 100W panel that puts out as much as a 130W panel when used with MPPT charge controller. "The unique combination of the AM100 and the Heliotrope Current Boosting series of MPPT Controllers will consistently exceed the charging amperage of standard 123 to 130 watt systems given the same operating conditions."

Back to your question, AM Solar uses 8 gauge twisted strand wire for up to 400W with a combiner box, larger installations they go to 6 gauge twisted strand wire. Daisy chaining panels outputs together can be damaging "terminal strips inside the junction boxes of most solar panels are only rated for about 15 amps. If you exceed this rating, you run the risk of literally melting down the terminal strip and stopping all charging."

Spike