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Adding to solar


Phaeton10

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Didn't want to highjack others thread so I thought I would start my own. I presently have 3 panels installed and in process of adding 3 more.

 

Current panels:

 

3- Kyocera KD 135GX 12 volt panels

 

VMPP 17.7V

IMPP 7.63A

ISC 8.37A

 

Adding these panels

 

3- Kyocera KD 140SX 12 volt panels

 

VMPP 17.7V

IMPP 7.91

ISC 8.68

 

I will mount these in 2 strings, 3 current panels on one side of motorhome and the3 new panels on the other side. I will be using a combiner box on the roof. The reason for mounting on each side is to help with shading, My three AC units blocks some sun where we boondock, either in the morning or the evening.

 

String each set with #10 wire to the combiner box and from combiner box to controller using existing # 6 wire approximately 18 feet. (Hopefully this #6 is large enough).

 

The fellow at Northern Arizona Wind & Sun told me the #6 would be plenty for this setup if I wired them in series. Hope he wasn't a car salesman in his former life.

 

From controller to (6) 6V battery bank is 18 feet again using #6 wire.

 

The controller is an Outback Flexmax 80.

 

My question is, which would be the best way to wire the panels in series or parallel?

 

 

 

Thank you in advance.

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The fellow at Northern Arizona Wind & Sun told me the #6 would be plenty for this setup if I wired them in series.

From controller to (6) 6V battery bank is 18 feet again using #6 wire.d

 

My question is, which would be the best way to wire the panels in series or parallel?

 

He was correct. 2 series arrays (and since it's already wired) #6 should be adequate. The controller to battery bank.. it depends. You didn't mention if you were charging at 12, 24, or 48v. At 12v, #6 would not be adequate.That's also assuming that the 18ft you stated was the up 'and' back leg. So a 9' physical as opposed to a 36' run.

 

For the best efficiency (and since the panels are slightly mismatched) it would be best to mix and balance the panels, but that's not really possible with 3 x 3. The next desirable would be two split arrays as you mentioned, but that would depend on your real estate. Any shadow on any one panel will severely diminish that's array's capacity. If you don't mind a 'morning' and 'afternoon' array that should work for you. The increased line voltage will also help efficiency, so there is that to consider.

 

A lot is open to debate and what works best for your particular needs. It sounds like you have a pretty good idea what you're doing, so only you can judge, but if it were me, and I had the real estate up top.. I would certainly try to make the dual arrays work. You've got some fairly long wire runs and the increased voltage would really help.

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I like your choise of panels - Kyocera makes great panels

 

I have them on my rig as well - also have then 135 and the newer 140

I went with a series parallel configuration - in many cases a good compromise for shade tolerance

Two in series then the pairs in parallel - The higher array voltage with it's reduced current vastly improves I2R losses

Vmp is about 35Vdc your Outback can easily handle this

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What the salesman said is ok.


I'm not clear on how you're connecting 2 separate PV banks to the controller. Series wiring is much easier, smaller wire, no combiner boxes and much higher voltage and reduced line loss. Those panel specs are so close it won't matter how you combine them.


With your shade problems, it sounds like your approach is good. Bypass diodes are supposed to shut down parts or all of the panels when shaded, but that's not always the case.


I run 6 panels in series @ 100+ vdc with #10 to an Outback 60, but I have no shading problems.

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Yarome that will be 18 feet total for each leg.

 

He was correct. 2 series arrays (and since it's already wired) #6 should be adequate. The controller to battery bank.. it depends. You didn't mention if you were charging at 12, 24, or 48v. At 12v, #6 would not be adequate.That's also assuming that the 18ft you stated was the up 'and' back leg. So a 9' physical as opposed to a 36' run.

 

For the best efficiency (and since the panels are slightly mismatched) it would be best to mix and balance the panels, but that's not really possible with 3 x 3. The next desirable would be two split arrays as you mentioned, but that would depend on your real estate. Any shadow on any one panel will severely diminish that's array's capacity. If you don't mind a 'morning' and 'afternoon' array that should work for you. The increased line voltage will also help efficiency, so there is that to consider.

 

A lot is open to debate and what works best for your particular needs. It sounds like you have a pretty good idea what you're doing, so only you can judge, but if it were me, and I had the real estate up top.. I would certainly try to make the dual arrays work. You've got some fairly long wire runs and the increased voltage would really help.

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OK, lets be crystal clear here.....

 

I would wire them as two series strings, unmixed. The difference in panels is not critical in this case. But you really don't want to go a lot bigger in difference. The referenced article is good to read and understand. I also cover it on my website. Hopefully in simple terms.

 

You can run the numbers through a voltage drop calculator, but I think you will find your wiring adequate (but I did not run the numbers). Just be aware that the shading will have a definite impact on harvest. The more you can minimize shading during peak sun times the better off you will be.

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You can run the numbers through a voltage drop calculator, but I think you will find your wiring adequate

 

From the arrays to the controller, I would agree, but an 18' run from the controller to your battery bank may be an issue. IMO

 

My calculator won't calculate losses above 5%, so I can't see a 12v 80amp charge on #6 wiring, but a 12v 80amp charge for 6m comes up to #2 @ 5% loss. A 24v 80amp charge for 6m comes up to #5 @ 5% loss. (none of the above are using the 125% rule)

 

To maintain a 1% loss, on a 24v charge would require 000. So #6 on a 24v charge wouldn't be terrible if a 5% loss is acceptable to you.

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I agree....I should have been more specific. I was thinking from the roof to the controller. An 18' run between the controller and the battery bank is not a good thing. But with heavy enough wire it will work. I sure would not design for that, though. You want around 1% on that run. 5% is not acceptable, to me anyway.

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Jack, I have no other choice as to where I had to mount my controller and the distance from my battery bank. So, from what I am reading on the responses, my wiring is OK down to the controller, but I am using a undersize wire from controller to batteries which will be a huge loss in power. I am not real techy on this, so what size should I be using from the controller to the batteries?

 

Thanks everyone for their assistance.

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so what size should I be using from the controller to the batteries?

You have around 800w, if they're all firing. Maybe you'll get 700w on a good day... so, 700/13= 54a maximum. From any ampacity chart, I read that #4 should do it. Assuming, of course, you're operating with a 12v battery bank.
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You have around 800w, if they're all firing. Maybe you'll get 700w on a good day... so, 700/13= 54a maximum. From any ampacity chart, I read that #4 should do it. Assuming, of course, you're operating with a 12v battery bank.

 

I have (6) six volt Duracell golf cart batteries from Sam's Club.

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From any ampacity chart, I read that #4 should do it. Assuming, of course, you're operating with a 12v battery bank.

 

 

You might consider wiring to the capacity of your solar controller (80amp).. not necessarily what you have up top at the moment. If you add/change panels in the future (even if you don't have room up top you might still consider a portal array) you wouldn't have the line capacity. The cost difference is marginal for the additional capacity.

 

Just my opinions, but if you're going to re-wire the controller to battery bank run, I 'would' recommend wiring to the controller capacity.

 

On edit: Of course.. you could just jump it up to a 24v bank which would both be more efficient, and require smaller wiring to push those 80amps. ;)

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Dropping the size of the end of the wire isn't a bad idea, less work and chances for a problem than splicing in a small pig-tail.

 

When I needed to reduce wire diameter in a situation like this I snipped strands from the center of the wire bundle and scrunched the outer layer down enough to go in the clamp. A tiny wire tie does a good job of keeping things scrunched down as you try to get it into the clamp.

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The way I read it, your manual states that #2 is the largest it can accept.

 

He can just use an automotive or inverter lug. I wouldn't buy from them.. just the first link that shows what I mean. You can purchase them in 'step' sizes. Ie., 2/0 to #1. I think they make the most surface contact for the best connectivity. Your local battery shop should be able to order whatever size you need.

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