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Author Topic: Solar panel connections  (Read 522 times)

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dfloeter

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Solar panel connections
« on: September 03, 2018, 05:54:22 AM »

I have installed a pair of 100w flex panels in the bimini each wired to a separate Victron MPPT controller. These controllers are mounted high in the aft port locker with the outputs joined and running forward with 6 ga wire to the panel.  Since the panel is fed by, I believe, by 1 ga wire , I reasoned at the time that the controllers would sense battery voltage at that point just fine.   
So, should I redirect the outputs straight to the house bank or does it not matter?   The run from controller to panel is about 15í while extending to the house bank would add another 8í or so.  Maybe this is splitting hairs but if I can increase output by some percentage it would be worthwhile.  Thx
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Dietrich Floeter
Traverse City MI
1996 Catalina 34 TR WK #1317
Universal M35A
Rocna 15

KWKloeber

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Re: Solar panel connections
« Reply #1 on: September 03, 2018, 09:01:28 AM »

(PS, Iím not a solar type of guy, so inquiring minds want to know)

Just wondering how you decided on 6 awg?

What would you see as the benefit of sensing or running charge current (all of about 15a absolute max possible) thru addl length of #6 versus the heavier feed cable, whatever gauge it is?
« Last Edit: September 03, 2018, 09:03:12 AM by KWKloeber »
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Jon W

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Re: Solar panel connections
« Reply #2 on: September 03, 2018, 12:43:09 PM »

To get the most benefit from your Solar panels they should connect to the house bank. When you say from controller to panel, is that the main distribution panel and is it connecting to the 1-2-Both switch? Where does the negative from the controller go, and what is its cable length? What are the positive and negative cable lengths from the panels to the controllers? The losses may be small, it comes down to what you want out of the system. Iím guessing you havenít done a voltage drop/losses analysis, hence the question? Posting a wiring schematic would be helpful if you have one.
« Last Edit: September 03, 2018, 01:03:26 PM by Jon W »
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Jon W.
s/v Della Jean
Hull #493, 1987 MK 1, M25XP, Manson Supreme 35
San Diego, Ca

KWKloeber

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Re: Solar panel connections
« Reply #3 on: September 03, 2018, 08:30:19 PM »

Jon

Why do you say that? Whatís better about connecting directly to the bank with #6 opposed to connecting with a #6, stepped up to a #1? 

Obviously the #1 will have less v loss than the same length #6. Are you saying that expecting a measurable v loss thri the connection to the #1?

-k
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Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
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Jon W

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Re: Solar panel connections
« Reply #4 on: September 03, 2018, 09:59:41 PM »

Hi Ken,

I like simple. The fewer connections in the system the fewer points of failure. I said the losses will be small, but hard to provide helpful input without a schematic.
« Last Edit: September 03, 2018, 10:07:58 PM by Jon W »
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Jon W.
s/v Della Jean
Hull #493, 1987 MK 1, M25XP, Manson Supreme 35
San Diego, Ca

J_Sail

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Re: Solar panel connections
« Reply #5 on: September 03, 2018, 10:18:11 PM »

At the charging currents you will get from a pair of 100w panels, the voltage drop is insignificant. You probably, though, want the connection to be such that the house bank gets charged regardless of the position of your master switch. I think that's why Jon is requesting a schematic.
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dfloeter

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Re: Solar panel connections
« Reply #6 on: September 04, 2018, 08:39:59 AM »

The number 6 wires terminate at a pos buss fed by the 2/0 wire straight from the battery bank and the neg attaches to a maybe 2 ga wire feeding the neg buss on the hull directly behind the panel.   I also prefer the fewest connections possible but with the size of wires so conveniently placed I didn't see the logic of running extra wire.   The pos buss was installed to better handle the 2/0 from the bank which was a little short and inhibited the opening of the panel for maintenance.  I did clean all connectors and made sure that the nuts stay tight for the best connections hoping to limit voltage loss.  #6 wire came in larger than required for voltage loss from the panels and I used the #6 because I already had a spool on the shelf and could see no harm in going larger.   

So far, I have seen a max current of 6 amps from these panels so the wires are definitely large enough.   These Chinese flex panels are under performing but I did not measure the output until too late to return them.    Short circuit voltage is 19.7 versus the 20.5 on the label.   My canvas guys velcro attachment tabs may be shading the panels a little in one edge and my next step is to pull the panels out in the totally open air and retest.   Meanwhile I think I have what I need and can carry on.   The logic that the controllers just need to sense battery voltage tells all and I think I get it now.  Thanks for the input guys.
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Dietrich Floeter
Traverse City MI
1996 Catalina 34 TR WK #1317
Universal M35A
Rocna 15

Jon W

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Re: Solar panel connections
« Reply #7 on: September 04, 2018, 09:49:55 AM »

Do you have a fuse between the 6 awg and the positive bus?
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Jon W.
s/v Della Jean
Hull #493, 1987 MK 1, M25XP, Manson Supreme 35
San Diego, Ca

dfloeter

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Re: Solar panel connections
« Reply #8 on: September 04, 2018, 10:59:19 AM »

Oh yes, I have fused all wires as they leave the source.   No fires on our boat, I hope.   No bears either and we stayed away from Heywood Island.   
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Dietrich Floeter
Traverse City MI
1996 Catalina 34 TR WK #1317
Universal M35A
Rocna 15
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