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Old 02-10-2016, 06:41 AM   #21
CaptnALinTiverton
 
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Default Re: Going Solar

I've had AGMs from original owner for over five years now without problems. Although I am a MSEE and like to keep with GELs as designed (I don't like changing original engineer's designs not knowing the thoughts that went into them), I'm not sure which way I'm going to go. I guess I'll keep researching.

As for solar, OldWest is right on about all other. One thing that doesn't seem right is the concern for real large wire size because a few hundred watts divided by 12 is only 17 amps so 14 gauge is good, or 12 gauge for longer runs.

AL
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Old 02-10-2016, 04:34 PM   #22
jackfish
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Default Re: Going Solar

I appreciate your credentials but I would caution readers about your assumptions regarding wire sizing for solar. The goals are to get an appropriate amount of PV output to the controller and from there to the batteries. AGM batteries require more than 12 volts (14.2 - 14.8) for appropriate charging and even 12 volt nominal panels can output up to 20 volts.
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Old 02-10-2016, 08:35 PM   #23
OldWest
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Default Re: Going Solar

I'm an armchair Internet parrot expert (read it on the Web so must be true). Think the various solar sites are focusing on the issue of voltage drop which is an issue with the lower voltages. Higher voltages may also experience voltage drop but will be a lower percentage (and amperage loads also are probably a factor).

Other poster above may be looking at the calculation of wire sizes based upon safety versus voltage drop.

Parroting handybobsolar.com and JackMayer, I think they were concerned that the appropriate size wires be used based upon size of solar panels and wire distances. Thinner wires would be fine from a safety standpoint but would lose charging power from voltage drop. Too fat wires would be a waste of money.

May have paraphrased incorrectly so check their websites.

Not so much on these thinner wires, but should also pay attention to proper crimping (especially for heavy inverter wires to batteries). Didn't follow all the ins and outs on crimping, but John Palmer in Florida had the right expensive crimping tool so could custom make the inverter to battery cables. If don't have the right crimper, can order cables from North Arizona Wind Sun.

As an aside, AMSolar used spade connectors at the end of the wires to the shunt for my meter. Problem with spade connectors is that they splay out when the screws are tightened so the connectors fall off. Closed circle connectors (where screw goes through hole) did not have that problem.

Spade connectors would probably be okay (would still prefer circles) if they fit into a slot or a recess so the tines could not splay out when screws are tightened.
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Old 02-10-2016, 09:37 PM   #24
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Default Re: Going Solar

Wire losses on the panel-> controller run are not very critical. However the voltage drop between the controller and the batteries is. Less than 1% voltage drop between controller and batteries at full charge current is ideal. This way the batteries receive an accurate charge profile, instead of one that is offset by voltage drops.

There are situations where Gel batteries are the best option. However, they are few. For most installations an AGM battery will perform as well or better. This is of course assuming your charging profile/settings is adjusted for the AGM batteries.
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Old 02-10-2016, 11:14 PM   #25
Boxster1971
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Default Going Solar

My 400 watt solar system from AM Solar came with 10AWG for run from panels to combiner box then 6AWG from combiner box to controller and to batteries. In use now for three years and running great.


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Old 02-11-2016, 02:30 AM   #26
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Default Re: Going Solar

Question - has anyone installed/ considered solar panel laminates like Uni-solar?
Seems like it would be more suitable for our roofs?
http://www.amazon.com/Uni-Solar-PVL-.../dp/B002MWFFWM
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Old 02-11-2016, 04:08 AM   #27
OldWest
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Default Re: Going Solar

Unisolar panels are not that efficient in wattage production per square area. Also, weird sizes. Double check that panels are still in production as corporate bankruptcies and asset sales to other companies.
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Old 02-11-2016, 05:25 AM   #28
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Default Re: Going Solar

As far as wire sizes go, the math is simple. If you divide the wattage by the voltage, you get the current available. Then you choose the wire size (resistance) based upon the maximum voltage drop you want to have at the current available. Yes, include voltage drop of connections. A good article explaining all this is at: http://www.westmarine.com/WestAdviso...e-And-Ampacity and they have many more excellent articles there, with skill levels given, including solar charging.

AL
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Old 02-24-2016, 03:56 AM   #29
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Default Re: Going Solar

Solar Panel mounting idea - sticky feet
https://rvsolarstore.com/index.php?r...product_id=112
Anyone used those yet?
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Old 02-27-2016, 09:27 PM   #30
OldWest
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Default Re: Going Solar

Have not used those.

One consideration is how much weight is being held by the square inch area of bracket.

Don't know how strong the fiberglass top is.

With semiflexible panels, very lightweight. Even with polycarbonate panel backing, still lightweight. Check OneManVan who used a special type of rivet bolt nut to affix. Don't know whether that rivnut? Would be a better choice versus 3M VHB metal bracket small footprint (I don't like making holes).

I used 3M Dual Lock (like Velcro but plastic mushrooms) around perimeter of my semiflexible solar panels--about 1 1/2 to 2" wide perimeter if I remember correctly--so the lightweight panels are held on over a fairly larger area. Also, not much uplift force.

But with fixed glass solar panels, weight and uplift might be an issue.

The plastic corners and middle plastic holders posted earlier may have a larger footprint--plus seemed a bit more aesthetic.

Just a thought.
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