Solar charge controller - Page 2 - Fiberglass RV


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Old 06-19-2008, 12:10 PM   #15
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Great! OK, I'm almost there. Where are you getting the 17.2 volts? In my owners manual for the Harbor Freight 45w array (three 15w panels) it says:


15 watts per panel, 14.5 volts output (working)
Peak Voltage: 23.57 OCV (Open Circuit Volts)
Nominal Voltage:14.5 volts battery output


How would one come to the conclusion of 17 volts, other than just taking it for granted that most panels are around 17 volts? (say theoretically I want to make sure mine isn't the one weird solar array that ain't 17 volts).
It appears that they have put a resister in series with the panel output to limit the current to around 1 Amp. With this low of a chargin current a charge controller isn't needed.
A series resister would explain the difference between open circuit volts (nothing connected) and Nominal Voltage: battery output (battery connected and charging).


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Old 06-19-2008, 12:34 PM   #16
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It appears that they have put a resister in series with the panel output to limit the current to around 1 Amp. With this low of a chargin current a charge controller isn't needed.
A series resister would explain the difference between open circuit volts (nothing connected) and Nominal Voltage: battery output (battery connected and charging).

I assume you arrive at 1 amp by taking 15w / 14.5v. So that means 3 panels would be about 3.1 amps, and 6 panels would be about 6.2 amps (90w / 14.5v), so I would need to use my 7 amp charge controller if I wired 6 panels in parallel? Am I getting the hang of it?
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Old 06-20-2008, 12:42 AM   #17
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I assume you arrive at 1 amp by taking 15w / 14.5v. So that means 3 panels would be about 3.1 amps, and 6 panels would be about 6.2 amps (90w / 14.5v), so I would need to use my 7 amp charge controller if I wired 6 panels in parallel? Am I getting the hang of it?
The answer is yes and no.

You're got the right idea in theory. In an ideal world what you say would be true.

There's one more bit of information that missing that comes from the practical world Things like charge controllers require an input voltage that's generally a couple volts higher than the output voltage. This is so that the control circuits can work properly. In your case the input voltage might be too close to the output voltage for the controller work. The only way to tell is look at all the specifications.
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Old 06-22-2008, 08:10 AM   #18
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I know just next to nothing about these systems.... but I'd like to ask what it cost you to install?

Scott, I am sorry it has taken me so long to reply. I have been away from my computer. The trailer was prewired for solar at the factory and my dealer charged $1169 for an 80 watt Sharp solar panel with a controller and that included installation.
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Old 06-25-2008, 02:04 AM   #19
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Scott, I am sorry it has taken me so long to reply. I have been away from my computer. The trailer was prewired for solar at the factory and my dealer charged $1169 for an 80 watt Sharp solar panel with a controller and that included installation.
If you're a good bargain hunter and handy with tools you can install a 50 watt system for $500 or less. My used 50w solar panel (eBay), charge controller, composite lumber (to build a new frame) and wiring ran about that much.


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Old 06-25-2008, 08:33 AM   #20
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thanks! it looks slick, I just have to justify the expense to myself... shouldn't be hard.
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Old 06-25-2008, 09:44 AM   #21
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We don't have our (3.1 amp) solar panel mounted permanently on our Casita. We just plug it into the pigtail... which, admittedly, means WE are the "charge controllers" (turn on the fan if it's a very sunny day - unplug it if the battery is up). YMMV, but it works for us!


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We put a suction cup at each corner of the panel, and stow it on the roof while camped.

It does mean we need to carry a step stool: the panel rides inside the trailer, on the big dinette table, when we're going down the road.

BTW, this pic is from a visit to a friend's place near Blue Mesa Reservoir, Powderhorn, Colorado!

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Old 06-25-2008, 07:09 PM   #22
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We put a suction cup at each corner of the panel, and stow it on the roof while camped.
Thanks for the idea Mary. Your timing is perfect, I was just about ready to rough in the wires for my solar setup. Now I know exactly what I want to do, and how I want to do it.
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Old 06-25-2008, 10:38 PM   #23
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We don't have our (3.1 amp) solar panel mounted permanently on our Casita. We just plug it into the pigtail... which, admittedly, means WE are the "charge controllers" (turn on the fan if it's a very sunny day - unplug it if the battery is up). YMMV, but it works for us!


Attachment 14055

We put a suction cup at each corner of the panel, and stow it on the roof while camped.

It does mean we need to carry a step stool: the panel rides inside the trailer, on the big dinette table, when we're going down the road.

BTW, this pic is from a visit to a friend's place near Blue Mesa Reservoir, Powderhorn, Colorado!
Suction cupping it to the roof is a fine idea . . . no muss, no fuss, KISS, and suction-cupped to the roof it's not likely to be stolen, either. I'd still get a charge controller, though; cheap solar charge controllers sell for under $30, so I'd tend to fork over the cash instead of having to plug/unplug my panel to keep it from overcharging and cooking my battery.
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Old 06-26-2008, 05:31 AM   #24
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A few questions for those who know what they're talking about to one who just started with solar power.
I am useing it just to keep my battery charged but as the same as Mary, have no controler as I was told that my small panel is really no danger to the battery?- True / False.

I finaly got a digital meter that I can read and understand but I do not know what a fully charged battery shoudl read for DC Volts.
What is fully charged?
What is in need of chargeing?
What is a dead battery?

I got me a 15 W panel and so far just set it up leaning against a gas bottle where the sunshine is comeing down, then I move it as the sun goes behind a tree branch, Do I need to keep moveing it into the little patches of sun on my camp site? True / False

This past week was the first week I used the panel with the new battery.
Unfortunatly I did not have the meter until the end of the week so I did not use the lights very much in the camper so I did not get a good before and after reading.
I will know better after this week of camping.
I go back tommorow so any answers will be helpful
Gerry
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Old 06-26-2008, 06:46 AM   #25
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Gerry
The battery voltage really depends on what type battery you have.
Standard batteries,AGM and Gel all look at different voltages for a full charge and they also like the charge to taper depending on several factors when charging.

Inexpensive charge controls will not have these extra features and that is mainly what you would be getting whith a more pricey,feature packed control.

That said,with a 15 watt panel and a standard sized battery I would think it difficult to damage the battery too.
I would still get even a cheapo control and not have to worry about it.

Another interesting thing to do with your meter is to connect it directly to the Solar Panel so you can see the actual D.C. output of the panel as you point it around. This can really educate you about the sunlight/output personality of the panel.

I velcroed a cheap meter to the back of a panel and using a PVC pole mount I made I am able to "Aim" the panel and see the result with the meter.
The difference is clear and obvious when you have it sighted correctly.

The panels do still make good voltage when in the shade but I was amazed at how much better voltage they can produce when properly sighted.

Of course this does change constantly throughout the day but I have a good time with it as I am getting something for almost nothing,almost.

Ed
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