Distance from panels to charge controller and cable size.

I know that the distance from the batteries to the inverter needs to be as close as possible, since it's DC current and there can be a lot of loss (the main reason Edison lost in the DC vs AC wars in the early days of electricity).

My question is: what about the distance between the panels and the charge controller? My panels come today, and I have several mounting options. If I mount them on top of my shed the angle and sun exposer will be perfect, and nobody will be able to see them. And it's not as high and difficult to get to as the roof of my house. I'm trying to avoid (at this point anyway) putting them on the ground so I won't have to mow around them.

The problem is this: I'd have to run 200 feet of cable to the charge controller if I mount them on my shed. Is that distance as critial as the battery to inverter and battery to battery distance? Also, what size of cable do I need? I know the battery cable needs to be large (I'm ordering premade battery cable to connect my batteries) for battery to battery.

Also, what about charge controller to inverter cable size? I'll have two 6volt golf cart batteries supplying around 290 amp hours to start, but will add to that later...

Views: 1186

Reply to This

Replies to This Discussion

This is the cheat sheet/chart I have used for years....

This chart shows wire distances for a 3% voltage drop or less. These distances are calculated for a 12 volt system. Multiply distances by 2 for a 24 volt system. Multiply distances by 4 for a 48 volt system.
NOTE : This chart is an approximate distance reference and is a little conservative. 


Amps    #12    #10     #8      #6      #4    #3     #2      #1   #1/0    #2/0

4           22.7   36.3   57.8   91.6   146   184   232    292    369    465   feet

6           15.2   24.2   38.6   61.1   97.4  122   155    195    246    310

8           11.4   18.2   28.9   45.8   73.1  91.8  116    146    184    233

10           9.1   14.5   23.1   36.7   58.4  73.5   92.8  117    148    186

12           7.6   12.1   19.3   30.6   48.7  61.2   77.3  97.4   123    155

14           6.5   10.4   16.5   26.2   41.7  52.5   66.3  83.5   105    133

16           5.7     9.1   14.5   22.9   36.5  45.9   58.0  73.0   92.0   116

18           5.1     8.1   12.9   20.4   32.5  40.8   51.6  64.9   81.9   103

20           4.6     7.3   11.6   18.3   29.2  36.7   46.4   58.4   73.8   93.1

25           3.6     5.8     9.3   14.7   23.4  29.4   37.1   46.8   59.1   74.5

30           3.1     4.8     7.7   12.2   19.5  24.5   30.9   38.9   49.2   62.1

35           2.6     4.2     6.6   10.5   16.7  20.9   26.5   33.4   42.2   53.2

40           2.3     3.6     5.8     9.2   14.6  18.4   23.2   29.2   36.9   46.5


So this chart is for panel to charge controller distance?

In the "amps" part, is that the amp output of the panel or the amp rating of the charge controller or something else?

That is amp output of whatever you are sending along that wiring. You have to have real honest vision when talking 200 feet, if you do it you don't want to do it twice. My suggestion, figure out a way to "not" do 200 feet. Re engineer the placement of your equipment. It's just not practical for 12 volt. If you insist John J.'s suggestion to up the voltage is almost a must.

I know we want the inverter to be as close to us, where we can see it, as possible. But keep in mind that these long runs are no problem for 110 AC. If you have to do the 200 feet, leave the inverter in the shed and do 110 volts to the house. But not that takes away your DC.

Let's find a way to keep it all at or near the house or only use your solar power in the shed.

I'd like to put everything in teh shed and run a 110 from theinverted to the house, but I live in Texas. I'm not sure that it's a good idea to put an inverter, charge controller and batteries in a shed where the temp can climb to 100 degrees with 70% humidity in the summer. The heat is death for the battereis and electrical equipment, right? If it's not, I'll keep it all out there. Otherwise I do have another option that will put the panels 20 feet or less from the batteries/charge controller/inverter.

200 feet? I'd consider 24v right off the bat.

This wire size calc might be of help.

Thanks for the link to that calculator. At 30 feet it tells me I need 9 guage... Sound right?

I see that my wire source tells me that the wire size for batery to inverter is based on inverter watt size. I want 2000 watts, so it looks like I need 1/0 size from battery bank to inverter.

So... we have 9 guage from panels to charge controller, 9 guage from charge controller to batteries, 1/0 for battery to battery, and 1/0 for battery to inverter. After the inverter I can step down to regular AC sized.

Does this sound correct for a 2 panel (2 of the 145 watt panels) system?

Which brings me to MC4 connectors for the panels and panels to charge controller. The ad on the right of the forum leads to some. But are there different wire guage sizes? Will these fit 9 guage wire?

I think you need to re figure that, 8 amps per panels, 2 panels equal 16 amps or a little less. Looks more like 6 gauge to me.

I would definitely be thinking about include a combiner box right from the start. You can step up your gauge at that point. Panels to combiner box then 6 - 8 gauge from combiner to controller depending on the distance from box to controller.

6 guage it is. Better a bit large than a bit small.

Combiner box to controller will be short. 2-3 feet.

I don't know what a combiner box is, or where to get one. Or why one would be required. Can you enlighten me?



Here is a picture of a home made combiner box made from parts found at Lowe's or Home depot.

This is not mine but I made one by looking at this picture.

Essentially what it does is allow you to bring in all your red + / black - leads from your solar panels into the box and "combine" them to the ground bar screws. Then you run your red / black BIG wire on the ends of the ground bars down to your charge controller. 

NOTE: For safety I put an automotive fuse holder with a blade fuse in it on my + wire run just before my charge controller. 

So what's the advantage of doing this?

A cool voltage drop calculator: http://www.nooutage.com/vdrop.htm


© 2016   Created by Renewable Ray.   Powered by

Badges  |  Report an Issue  |  Terms of Service