Questions about solar power - Page 12 - Fiberglass RV


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Old 03-15-2014, 07:15 AM   #155
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Regarding the flexible solar panel, the one from China has an aluminum sheet backing.
Where as the Renology flexible panel has a plastic back sheet.
Seems like the aluminum would be far superior.
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Old 03-15-2014, 07:21 AM   #156
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Mechanically, the aluminum might seem to be better, but it depends on the use. I'm not going to move my panels, but with constant bending/folding the aluminum would weaken and possibly break. The aluminum might also heat faster/hotter than the plastic back, which would drop the efficiency of the panel.
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Old 03-15-2014, 07:54 AM   #157
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Thanks... good info.
I was thinking I could "tape" the alum. ones to my fiberglass roof.
No holes, no brackets.
Not sure about "taping" the plastic ones.
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Old 03-15-2014, 08:24 AM   #158
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Questions about solar power

3M has many different VHB tapes. Some will even stick to polyethylene.

Also note these are flexible enough to, say, conform to a cambered trailer roof but can't be bent very much, certainly not folded.

Amorphous panel are much more flexible, can even be rolled onto a tube Less than half as efficient though so they require at least twice the area for the same output.

I'll post some detailed pics of the Renogy panel next Thursday when I get back to my daughters house where I had it shipped.
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Old 03-15-2014, 08:45 AM   #159
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Some of the plastic-back manufacturers recommend an adhesive - some are even peel-and-stick. I've seen the applications, and they look good - integrated into the roofs of the trailers so they're more aerodynamic than the tilt-mounted ones.
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Old 03-15-2014, 09:42 AM   #160
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Simply add one more panel if you want to go many more days than 3 or 4.
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Old 03-15-2014, 09:48 AM   #161
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Unless I've missed something in the post here, I haven't seen much about the quality of solar panels. Any thoughts ?
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Old 03-15-2014, 09:59 AM   #162
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I was wondering the same thing, and not just concerning the semi-flexible. There are some pretty big $ differences on like panels. One can buy a Renogy 100w rigid panel for $150 where as a Grape 100w goes for $250.
Amazon.com: RENOGY 100 Watt 100w Monocrystalline Photovoltaic PV Solar Panel Module 12V Battery Charging: Patio, Lawn & Garden
Amazon.com: Grape Solar GS-S-100-TS 100 Watt Monocrystalline Off-Grid PV Solar Panel: Patio, Lawn & Garden
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Old 03-15-2014, 11:44 AM   #163
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Go to Home Depot if you are interested in Grape Solar.
Order over the internet from HD.
Free shipping to your nearest store.. 90 day return.
GS latest panel is Fab 8, 105 watt for $160 if I remember correctly?
Plus they have a Fab 8, 160 watt, also available from HD.
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Old 03-15-2014, 12:28 PM   #164
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Stev, Thanks for that tip I appreciate it. I found it on HD's site for 149.00, but it doesn't come with a frame. Amazon has the same panel for 139.00 shipped(not sure if fab 8) and it looks like it comes with a frame. I've been looking at 95-100 kits but wouldn't mind getting things separate if I can save some money. I have looked at kits ranging from 250.00 to 700.00 that's why I ask about quality and if it really matters or not. One of the more expensive ones come from a Canadian company but they also look very well made and put out the amps. It may be hard to beat the kit prices from Solarblvd, and I could always get a inexpensive mppt like the one Peter used. I was actually looking at that one on Amazon for 68.00. I can see this might take some time to sort out, or just dive into one of the cheaper kits from China and see how it works.
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Old 03-15-2014, 01:23 PM   #165
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Here is the one from HD..
Grape Solar 105-Watt Monocrystalline PV Solar Panel for RV's, Boats and 12 Volt Systems-GS-S-105-Fab8 at The Home Depot
It is 105 watt, Fab 8, it has a frame.
Have it shipped to your nearest store.
You have 90 days to look it over. Take back to store.

Actually the cheapest way, and if you want to save money, is to buy a kit.
The only chance you take is, once you get it, thats about it. Would be hard to return.

Kits have wiring, support mounts, connections, etc. All that adds up.
If you buy the panel alone and start adding on with all the rest of it, will cost you more I am sure. But quality may be better.
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Old 03-15-2014, 01:42 PM   #166
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Stev, Yes I do see that its a 105w and that will also work for me and has frame. Only reason I would buy separate components is so I could go with different length wire and maybe go with a mppt controller. You are right that getting delivered to HD would be nice then you can check to make sure its in one piece too, and the 90 day return is nice .
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Old 03-15-2014, 02:07 PM   #167
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There was a question, a few posts back, about why a battery's charge level makes a difference in how quickly a battery sulfates. I'm going to try and answer that question in layman's terms.

=====

How well charged a battery is and how quickly it forms battery killing sulfate is related to the chemical and physical properties of lead, which is a "multivalent" metal that has multiple forms with subtly different properties.

Lead(II) (the dominant form) and lead(IV) (more exotic) are both soluble in strong, concentrated acids, but their solubility drops off as the acid becomes more dilute. Lead (IV), the version of lead that's responsible for battery sulfation, is much less common than lead (II) but it's also more sensitive to the acid concentration.

The chemical reaction that stores and releases the a battery's electrical charge creates or consumes acid from the battery water. As you charge a lead/acid battery, you convert lead(II) sulfate and water into lead and sulfuric acid. When you discharge a lead/acid battery, you convert water, sulfuric acid and both lead(II) and lead(IV) into lead(II) sulfate (the good kind) and lead(IV) sulfate (the bad kind).

This is how electricity is released and stored in your battery. When your battery makes lead(II) sulfate, it binds one atom of lead(II) and one sulfate "ion" from the battery acid to release two electrons. In the process, it makes lead(II) sulfate.

The nice thing about lead(II) sulfate is it is pretty easy to reverse this reaction by simply pumping two electrons back into your battery to break the union up and restore charge to your battery.

As I said earlier, there are different forms of lead. Most of the lead in your battery tends to form lead(II), but some of it becomes lead(IV), and lead(IV) can also bind to sulfate ions and release electrons. When your battery makes lead(IV) sulfate, it binds one atom of lead(IV) and two sulfate ions to release four electrons.

Reversing the lead(IV) sulfate reaction is much more difficult, because the electrons have to "attack" two connections, or bonds, between the lead and sulfates simultaneously. It's about seven times harder to convert lead(IV) sulfate back into lead and acid as it is to convert lead(II) sulfate back. (For engineering geeks, the ratio e˛:e⁴.)

Now here's the tricky part. As you use up the charge stored in your battery, the acid in your battery water becomes more dilute, and that increases the likelihood that a lead(IV) atom, which prefers more concentrated acids, will be used to make bad-boy lead(IV) sulfate. The more charge you use, the more likely it is that lead(IV) sulfate will form.

When your battery is really, really discharged, things get even worse. Starting at 20-40% of full capacity (depending on battery construction and additives the manufacturer has added to the battery water to prevent it), the battery acid is so dilute that lead(IV) really, really wants to get out of solution, so desperate that it'll actually force two lead(II) sulfates to revert back to their non-sulfate form and donate their sulfate structures to the lead(IV) to, forming bad-boy lead(IV) sulfate, greatly accelerating the process of sulfating your battery.

=====

This is, very obviously, a technical topic, and I've necessarily glossed over a lot of details, but it is an accurate description of what's going on inside your battery. I'd love to know how well people followed what I was saying.
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Old 03-15-2014, 02:10 PM   #168
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Quote:
Originally Posted by Mike Magee View Post
It has been my understanding that a PWM controller discards the additional voltage, whereas a MPPT controller will utilize the higher voltage to push more current (with some internal losses due to power consumption of the MPPT circuitry). Which would seem to suggest that a 21V, 3A input would be turned into something like a (roughly) 14V, 4A output. Yes, no? Discussion?

You are correct. An MPPT controller will make full use of the dollars paneks capability by matching the current and voltage to what the battery can absorb.

Aside from small losses in the conversion higher voltage is converter to more amperage.

Power (wattage) = E (voltage) x I (current)

In your case 21 volts x 3 amps = 63 Watts

At 14 volts: 63 watts/14 volts = 4.5 amps less conversion losses. Assume 95% efficiency you can expect to see 4,3 amps .
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