voltage drop calculator

[niel]

i'll second my thanks as i had already sent the first by pm.

[THENEXTVETTE]

Hey All,

This calculator I found you just plug in the length and amps and it gives you numbers ! lol It runs in JAVA so no need to DL another program.

Thanks again for all the info
Bernie

http://www.stealth316.com/2-wire-resistance.htm

[niel]

hi bernie and to all else as well,
i should point out here that the calculator this thread was created for was not one just grabbed someplace off of the net as it was created with formuli and data that i gave and another person with the spreadsheet layout had worked on. it is rough on its delivery as it beckons a bit of understanding in its use, but encompasses allot of info and aspects not always found on other calculators and with high accuracy. i am not saying another calculator won't do this and i'm not jealous of another calculator either, but i don't want this thread to wind up being a conglomerate of on the net calculators and i don't just say this to you bernie as it needs said to all. let's keep this one about the calculator i helped to create. others are free to create another thread or even to make references to another calculator here for comparative purposes. i hope this doesn't sound too harsh and i hope you all get that i want this thread for primarily this calculator.

[scrubjaysnest]

Tried out V drop calculator niel and it comes out close to using the tables from my 1970 ARRL handbook. It is very close to real world on my 2 panel 160 watt RV system with Sunsaver 10 controller. The question I see is the gain in current through the controller. The amps out appear to be based on watts in = watts out which would be ok for a large array with mppt but doesn't seem that way with my real world measurements. I measure the same current into the controller as I get coming out. By the way with today's sun during the test the panels only produced 135 watts not the 160 expected so it wasn't a perfect solar day. The battery did reach full charge after starting at about 50% SOC.
I say about as I don't have a hydrometer with me so couldn't check SG.

[niel]

scrubjaysnest,
there are probably differences due to the fact i design for higher temps on the wires. they are most likely giving figures for 25 degrees c from the arrl. also, just because one has an mppt controller does not mean that one will not see lower figures at times, but i'm not there to say what may or may not be right with what you are seeing.

[scrubjaysnest]

You are correct there, I saw a note that said wire type and temperature effects the ratings and to see the NEC tables to correct. The bottom line is my first system is doing as expected over all. I checked the battery voltage after setting over nite and with air temp of 61 degrees it showed 13.09VDC.

[Skippy]

I found the link to this under one of your replies (well ALL of your replies) and thought I would give it a try...

Changed the values for 12 V array, 12 V battery, Used #4 wire for everything.. just not sure what the # of feet for string 1 would be ? I just plugged the cables that came with the panels into the combiner box with a 6" piece of #6 , - is that what you mean ?
So with that info plugged into the converter, I have a voltage drop of 0.355 from Array to Cont. and .396 from Array to Bat. Not bad, if I did it right

Thanks for the link, it is now saved on all my machines

[niel]

skippy,
all interconnecting wires in a string need accounted for as well as the wire runs to the cc and batteries. say for instance you have 3 pvs in a series string for string 1 and they each have 2 36 inch #10 copper wire pigtails for connection. that would be 6 total at 3ft apiece for a total of 18ft at whatever v drop % that equates to. add to that the wire that connects from the ends of the pigtails in the string to go to the combiner even if it is only 6 inches. if it is 6in then that is 6in x 2 = 12in or 1ft at whatever v drop loss is for that section. when you encounter the combiner you must remember that it combines the amperage of all strings that go to it and thus changes the overall v drop % for that wire run to the cc.

as i've stated in other places when you have multiple strings, do not add all of the individual string v drop %s together. pick the longest or worst one and figure it from that. if that turns out to be an acceptable v drop % when added to the rest of the circuit to the cc and batteries then you know the other strings will also show to be good too all things being similar such as wire gauge, pv watts, etc. if the worst string turns out to be too high then that needs a better wire solution, be it the run to the combiner and/or making the other wires shorter/bigger thicknesses. if that's unfeasable in the string itself then changes need made with the other wire runs to compensate. also, if that worst string's v drop % is bad then the others are suspect as well and may need computed. it can seem complicated, but it's not. the description is what is hard to get across to those that aren't familiar with electricity or electronics.

i can't confirm or deny what you figured as i lack the full information needed to do so.

[CATraveler]

Thanks to everyone that made this calculator available. I've used it compare various configurations of wiring, panels, etc. and it's very adaptable for that purpose. I like to document and save the results and the protected cells don't allow documentation. So I suggest unprotecting row 1, column k and remaining columns and the rows below the notes.

Protecting the calculations is probably a good idea. I did remove the protection mainly to add my comments and of course checked the calculations.