Solar panel is hooked up and working! - Page 2 - Fiberglass RV


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Old 04-21-2013, 11:53 AM   #15
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If you have any connectivity problems, it will be at the crimped connectors.

Keep an eye on them, as they tend to not like being bent, wet or tugged. I always use soldered connections with shrink tape over to insulate and distribute the stress.

Rail on Byron.
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Old 04-21-2013, 12:04 PM   #16
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Quote:
Originally Posted by Byron Kinnaman View Post
You did the right thing by using crimp connections. Solder is not a good electrical conductor. It's used a lot but if you look around your tow you won't find any solder connections or in your computed (the traces on a printed circuit may look like solder but there's copper and gold below the solder).
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Originally Posted by Thomas G. View Post
If you have any connectivity problems, it will be at the crimped connectors.

Keep an eye on them, as they tend to not like being bent, wet or tugged. I always use soldered connections with shrink tape over to insulate and distribute the stress.
Byron and Thomas, Thank you for your input.
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Voice your opinion respectfully and then let it go.
I hope this is 'nuff said.
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Old 04-21-2013, 12:13 PM   #17
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I don't see how the information at Basic Tutorials: Wires and Cables for Solar Energy Systems
can be taken as other than a contrdiction of Brian's views and Mike's choice of conductor between panel and controller? Looks like a Tevye situation to me. What am I missing?

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Old 04-21-2013, 12:34 PM   #18
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Solder

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Originally Posted by Thomas G. View Post
If you have any connectivity problems, it will be at the crimped connectors.

Keep an eye on them, as they tend to not like being bent, wet or tugged. I always use soldered connections with shrink tape over to insulate and distribute the stress.

Rail on Byron.
I agree with Thomas , in my forty years as an electrician I have seen many crimped splices go bad especially where moisture or vibration is present.
I make a western union splice , solder the splice and cover with shrink tube listed for wet & underground locations . Also there are two types of crimping tools * T&B indenter style costing $40.00 and the common home improvement store model costing $10.00 . I prefer the T&B for splicing and the other style for cutting screws which is all it's good for
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Old 04-21-2013, 01:35 PM   #19
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I don't see how the information at Basic Tutorials: Wires and Cables for Solar Energy Systems
can be taken as other than a contradiction of Byron's views and Mike's choice of conductor between panel and controller? Looks like a Tevye situation to me. What am I missing?

jack
This site is pretty conservative, although it is best to err on the side of bigger wires to minimize losses. I use a chart like this:
Electrical Wire Gauges to determine total resistance (50 foot cord is 100 feet of wire) then calculate voltage drop or power losses (I^2*R) .
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Old 04-21-2013, 01:54 PM   #20
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I am absolutely certain that I could have done some things differently to improve the setup, but I am not that particular about small losses. If I ever have problems with the crimped connections (someday), I'll re-do them. Anyone who is a perfectionist, please turn your eyes away from my solar setup so as not to aggravate yourself. Fact is, I'm happy with it.

About crimped connections: the 7 pin receptacle's hidden backside consists of 7 terminals (of which I used only 2) with screws. When the wire is inserted between the two pieces of plated steel and the screw is tightened, it crimps down on the wire and holds it in place. Is this not a crimped connection? Yet this common receptacle, used on thousands and thousands of tow vehicles, is designed to function this way... and they do! Methinks crimped connections must work reasonably well.
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Old 04-21-2013, 01:57 PM   #21
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What's the effect on choice of conductor size of having controller as close as possible to panel (talking distances inside junction box common to panel and controller) and the battery at large multiples of this distance, say 50', from both?

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Old 04-21-2013, 02:06 PM   #22
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Originally Posted by rabbit View Post
I don't see how the information at Basic Tutorials: Wires and Cables for Solar Energy Systems
can be taken as other than a contrdiction of Brian's views and Mike's choice of conductor between panel and controller? Looks like a Tevye situation to me. What am I missing?

jack
Look at it this way. You're camping and you need a half-pail of water. You walk to the campground's spigot (halfway across the CG) and fill your pail 7/8 full. On the way back, 1/8 of the water sloshes out while you carry the pail. When you get back to the trailer, you have 3/4 pail of water. Recall that you only needed 1/2 a pail. Do you get upset about losing 1/8? I hope not! After you use your 1/2 pail, the rest might even get dumped out if you don't have room for it.

That is what's going on here with the voltage. I need 14.1V at the controller; any more than that is wasted. The panel puts out up to 18V. But the delivery method lets some slosh out, so maybe only 16V arrives. The current still gets delivered, just not at as high a voltage. Do I need to rework my wiring to avoid losing 2V? Nah, I don't need it. The PWM controller dumps the excess voltage.

Now, if I had a MPPT controller, that could take the extra voltage and use it to boost current flow into the battery. But at what expense? And the logic circuitry uses up some of that current internally, so waste still exists. The MPPT controller only pays off when more solar panels are present (and needed).
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Old 04-21-2013, 02:12 PM   #23
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What's the effect on choice of conductor size of having controller as close as possible to panel (talking distances inside junction box common to panel and controller) and the battery at large multiples of this distance, say 50', from both?

jack
I could improve performance slightly (1.5%?) by attaching 1 foot long leads of 6 or 8 gauge wire from the controller directly to the battery terminals.

50 feet or even 75 feet of 16 gauge wire between the controller and panel should not reduce performance appreciably. 100 feet is a 3.5V drop, though.
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Old 04-21-2013, 02:23 PM   #24
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Good dry camp analogy, Mike and I understand tour conclusion that the losses involved are not appreciable in the case of a 12V battery. It could be that site I linked to assumes 24V storage. That part isn't mentioned; smallest recommended conductor mentioned is 12awg.

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Old 04-21-2013, 02:27 PM   #25
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From Thomas' site 16 ga. R= 4.1 ohms/1000ft

so R=0.004ohms/ft

@ 25 ft two conductors there is 50ft of wire ( Byron used 25 ft. For 50 ft just double.)

Rt=0.004 x 50 = 0.2 ohms

75 watt panel........ Assume I max 5 amps

V=I x R= 5x0.2=1volt

16 ga is what I would use. Light, flexible and cheap. This same discussion occurred when another member asked the same question. I said 16 ga lamp cord. One individual suggested 10 ga romex! I think the poster used a 12 ga extension cord. His money.

On soldering. I prefer to solder and have not had issues but on the road I carry a crimping tool. No AC. Soldering is an aquired skill. Crimping is probably better for the neophyte. I have never used Scotch locks (loks?). While being a big fan of 3M products, they just don't look good to me. Raz
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Old 04-21-2013, 02:42 PM   #26
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Quote:
Originally Posted by Byron Kinnaman View Post
Solar panel voltage is above 20 volt out put.
With an open circuit, yes. It would be very surprising if this were the output under load.

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I was envisioning that the controller would take the higher voltage and translate it into a current boost as it stepped the voltage down for the battery. But PWM controllers don't do that, do they? Only MPPT controllers do that.
Correct. A basic controller is just a switch; a non-MPPT PWM controller is essentially a throttle.

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So yeah, as long as the long cords from panel to controller deliver at least 14.1V (set point of this controller is 14.1, not 13.9), the voltage loss they cause is pretty much inconsequential.
If the panel output measured at the controller input is over 14.1 V, it will just be throttled down... but is it really higher than that under load (while delivering charge current to a run-down battery)?
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Old 04-21-2013, 03:03 PM   #27
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Correct. A basic controller is just a switch; a non-MPPT PWM controller is essentially a throttle.
Interesting. I have an old charger that uses PWM. I've always assumed the off time was to provide the sensing circuitry with a "disconnect" to check the battery voltage and the lowering of the duty cycle was to slow the charging down to avoid overheating the electrolyte. I'm not sure what you mean by throttle.
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Old 04-21-2013, 03:10 PM   #28
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Voltage drop is not the only concern with wire size . Mechanical strength plays a factor IE smaller wire breaks easier than larger wire . Wire connectors which utilize set screws are not considered as a crimp connection . Crimp connections are not reversible
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