PWM controller question

jrnymn7 wrote:
BFL,

Yeah, to avoid excessive volt drop, I'd like to go heavy cable, at least 8ga, maybe 6ga even, provided I can get connectors for that gauge wire? And I'm not sure if they all require a special crimping tool.

I'm looking to go 50', for best portability.

I was even considering going with 4 panels, and using them as window awnings. :)

The thing with portables on the ground is the Rv itself blocks off the sun at times, so you have to move the portable to the other side of the trailer during the day. That means you need about half again as long a wire pair as the length of the Rv in practical terms.

You can't always put the panels on the South side, you might have to put them in the neighbour's site to get free of the shade, etc, and even on the south side of the RV that can restrict the panel to a 180 E-W view when in summer the sun goes around more than that more like 210 degrees. So the panel can "see" the sun all day you have to get it farther out from the RV.

The best was getting my tracking contraption on the roof so the panel can see all around.

I use long but fat jumper cables as my panel to controller wires with pigtails on the panel and controller to clamp to. I forget the gauge of wire but it is heavy 1 or 2 al-cu with monster 600a parrot beak clamps :) Every so often they come on sale at Princess Auto. More length needed, I just tack on another length of jumper cables clamp to clamp.

Only thing is now instead of red and black, they are pink and black due to the UV.

My 130w panel when on the RV roof was to 45 ft pair of #8 down through the trailer to the battery compartment where I had the controller nearby. I still got full Isc amps from the panel at that distance. For the two 140s in parallel I imagine #6 cu would be ok

PWM can take some voltage drop (panel to controller) and still do the amps, unlike MPPT which needs the voltage more. they both need low R wiring to the battery so the controller set-points are on the mark.

this is the best calculator as it is clear about pairs and one way distance, not confusing about whether round trip or not like other calculators (ISTR tenbear gave us this one last year)

http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=2.061&voltage=12&phase=dc&noofconductor=1&distance=60&distanceunit=feet&eres=8&x=42&y=5