Solar panel is hooked up and working! - Page 3 - Fiberglass RV


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Old 04-21-2013, 03:20 PM   #29
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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
What do you think about scotch lock?
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Old 04-21-2013, 03:28 PM   #30
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Is the Scotch Lock what are commonly referred to as suitcase connectors?
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Old 04-21-2013, 03:38 PM   #31
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I've always assumed the off time was to provide the sensing circuitry with a "disconnect" to check the battery voltage...
I don't think the small fraction of a second of "off" time is enough to be useful to check battery voltage.

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... the lowering of the duty cycle was to slow the charging down to avoid overheating the electrolyte.
Adjusting the width (time duration) of the "on" portion of the cycle is how a PWM controller works - it depends on the switching between fully on and fully off being frequent enough that the result is essentially being partially on. Yes, the purpose of not being fully on in any controller design is to keep the current to a safe (for the battery) level (which of course is nearly zero when fully charged).

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I'm not sure what you mean by throttle.
Sorry, that was supposed to be a helpful analogy, not a source of confusion...
A throttle valve - such as the throttle on a gas engine - limits the flow by being partially closed by an adjustable amount. A PWM controller acts like an electrical equivalent, allowing some fraction (up to 100%) of the "flow" that direct connection would.
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Old 04-21-2013, 03:42 PM   #32
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Is the Scotch Lock what are commonly referred to as suitcase connectors?
I've never heard the term "suitcase connectors", but it makes sense: the connector body hinges closed over the pair of wires being connected... so yes, that would be a Scotchlok (using the 3M brand name) or insulation-displacement connector.
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Old 04-21-2013, 03:46 PM   #33
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Good article here on controllers. RV Solar System Charge Controllers | PowerMyRV


The throttling effect that Brian is referring to might be clearer with this illustration:

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Now let’s take a look at the fundamental operation of a PWM controller. These controllers use a Pulse Width Modulation scheme, aka Duty Cycle Change, to directly connect and disconnect the panel to the battery. When “on” the panel and battery are directly connected together.
The repetition or operating frequency is fixed by the green hash marks, while the on versus off duration, aka duty cycle, varies depending on how much charge the battery requires. Note when the waveform is high the panel and battery are directly connected. The panel’s voltage drops to the match the batteries voltage when connected together.
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Old 04-21-2013, 03:46 PM   #34
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Is the location of the controller the prime consideration in determining the conductor size required, Brian?

jack
Not necessarily. My controller is mounted on the solar panel. Then I have about 12' of wire to the battery, and can add another 15' if desired. Even that way the wire resistance is a not a concern since the maximum current is in the 4 to 5 amp area.

I chose to put the controller on the solar panel since I charge more than one battery in different locations. One battery in on the tongue of trailer and other sits in the back of the truck. I have short pig tails on each battery with the same connector (Anderson Power Pole) and mating on the cable from the controller. Makes it very easy to switch from charging one battery to charging the other.

There's a lot of misconception about wire size and gain by going to larger sizes. Yes there can be a little gain, but very little and usually not worth the cost of the copper. There might be cases where you gain a bit more, but knowing Ohm's law and reading resistance/ft(often listed as ohms/1000') charts can give some sort of idea how much gain.

I'm using 12 awg wire only because that what I had for ham radio operations, where I need a peak of 22 amps, so used what I had left over. The larger Anderson wire has some pretty thick tough insulation which withstands abrasion better.
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Old 04-21-2013, 03:48 PM   #35
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I try to stay away from scotch locks mostly, but have used them for an interior application.
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Old 04-21-2013, 04:40 PM   #36
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I don't think the small fraction of a second of "off" time is enough to be useful to check battery voltage.
In the electrical world milliseconds are a long time. All chargers be they analog or digital sample battery voltage and compare to a preprogrammed value. From my readings electrolyte temperature would be a better measure. (Perhaps there is a chemist in the house that would comment) That's my gripe on smart chargers but that's a different discussion.
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Old 04-21-2013, 04:44 PM   #37
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I have a rig nearly identical to Byron's--80watt single panel with the controller mounted on the junction box rear of panel, 22' of 12awg SG connects to pigtail on the battery, A-frame leg on the back of panel. I used common calculator formulas from solar suppliers to calculate. Perhaps, despite my ignorance of theory, I have "erred on the conservative side" and avoided bottle necking my setup despite the location of the controller. Anyone concur, disagree?

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Old 04-21-2013, 04:50 PM   #38
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In the electrical world milliseconds are a long time.
Yes, but in battery electrochemistry it is a very short time, which is why a resting voltage is measured after many minutes, not a few milliseconds. My understanding is that multi-stage "smart" chargers watch the current/voltage relationship to determine where they are in the charge cycle, not an assessment of non-charging voltage.
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Old 04-21-2013, 05:12 PM   #39
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........Anyone concur, disagree?

jack
I think ya done good, Jack

I know that generally it is recommended to put the controller close to the battery, but using heavier wiring would help to mitigate the controller being on panel from being a problem
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Old 04-21-2013, 05:29 PM   #40
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In the electrical world milliseconds are a long time. All chargers be they analog or digital sample battery voltage and compare to a preprogrammed value. From my readings electrolyte temperature would be a better measure. (Perhaps there is a chemist in the house that would comment) That's my grip on smart chargers but that's a different discussion.
Some solar controllers have a temp probe that is placed in the battery box, and the controller's output is based partly on that temperature.
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Old 04-24-2013, 01:08 PM   #41
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Properly crimped connections work well in dry locations. If moisture is allowed to wick into the splice oxidation could build on the surface of the wire and connector. The joint will get a fuzzy appearance. In theory this could cause resistance and subsequent voltage drop and in worst case an open circuit. This could happen with crimp on connectors, Scotchloks, wire nuts, wound wire splices, etc. Even the 7 pin set screw connectors could be subject to moisture.
Wire nuts made for outdoor use are filled with "goop", and dielectric grease can be used on the set screw type connectors. I solder and shrink all my automotive connections and have had no failures so far, but I'm only 67 so it still could happen.
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Old 04-24-2013, 02:08 PM   #42
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Any one got an aspirin?..........lol.

This as set me back to 'industrial electronics' school. lol.
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