Lance 1181 solar install?

keefr wrote:

Does anyone have any real life experience with this partial shading effect?

That's a good question, and one to which I'd love to see the answer. On my 5'er I have 6 12-volt panels set up in 3 24-volt pairs, so I get the best of both worlds. If you had room for 4 panels on the TC, 2 24's would be the way to go. On my TC I have 2 12-v panels in series, and my seat-of-the-pants feeling is that I get better charging than when I had them in parallel.

Thanks for the feedback....I had also thought of that, but I doubt that I have room for 4 panels. I haven't done serious layout measurements yet, but the series/parallel combo would be a good alternative.....and no more current from the panels than just having 2 panels.
There is also some good deals on 250W 24 volt panels that might give similar results.

Does anyone have any real life experience with this partial shading effect?

That's a good question, and one to which I'd love to see the answer. On my 5'er I have 6 12-volt panels set up in 3 24-volt pairs, so I get the best of both worlds. If you had room for 4 panels on the TC, 2 24's would be the way to go. On my TC I have 2 12-v panels in series, and my seat-of-the-pants feeling is that I get better charging than when I had them in parallel.

keefr wrote:
If you go with an MPPT controller, you can wire your panels in series for 24v to the controller (Actually will be about 34 volts), and the controller will drop it to the proper battery charging voltage without much loss. Higher voltage in the wire means less current, so thinner wire will work. EP Solar makes an MPPT controller that will take up to 100 volts in. You could have 4 panels in series and at 60 volts in, 300 watts would only need 5 amps - well within the capacity of 12 ga. wire.

I think this would be the way to go if it weren't for the issue of partial shading. You would have less loss of power at the higher voltage because the current to the charge controller would be reduced. (The loss on the wire is equal to the current times the resistance. So, if you can reduce the current OR the resistance you are going to reduce the loss.) (This is why they do such high voltage on the power grid transfer lines.....to reduce the loss. AC has much different characteristics than DC in this regard, however.)

I won't have the luxury of parking in full sun a lot of the time, and with the series connection any panel that is partially shaded reduces the output of all panels.....With parallel panels, the panels that aren't shaded still produce their full output, but you will be at the mercy of higher current to the charge controller and therefore more loss.....unless you increase the wire size.

Does anyone have any real life experience with this partial shading effect?

If you go with an MPPT controller, you can wire your panels in series for 24v to the controller (Actually will be about 34 volts), and the controller will drop it to the proper battery charging voltage without much loss. Higher voltage in the wire means less current, so thinner wire will work. EP Solar makes an MPPT controller that will take up to 100 volts in. You could have 4 panels in series and at 60 volts in, 300 watts would only need 5 amps - well within the capacity of 12 ga. wire.

Hi,

Figure out the voltage drop from 17 down to 14.4 volts.

gpascazio wrote:
You are correct 12 Ga is way too small abandon it. I think this is the most important obstacle that you will have to overcome with RV Solar. Just in case you haven't seen these sites before I have included some links:
http://www.amsolar.com/
http://nooutage.com/vdrop.htm
http://www.where-rv-now.com/Notes/Solar/index.php#Calculator
http://www.rvsolarelectric.com/index.php?route=directory/directory&directory_id=3
http://www.jackdanmayer.com/rv_electrical_and_solar.htm

Thanks for the very interesting links.....especially the voltage drop calculator. You can very well calculate how wire length and gauge make a huge difference......with 25 feet of 12 gauge wire, 12v and 14A, 9.1% is being lost.
I'm a little under the weather today, so haven't yet full explored the others.

PIANOTUNA......I'm not sure I understand why the loss wouldn't be as important with PWM. It seems to me that with voltage loss also comes current loss either way?

Hi,

The voltage at the battery pretty much determines what the panel voltage is with PWM controllers. Since the commonly used lowest voltage panels are 17 volts, voltage drop from wire is not much of a concern, so long as the wire is rated for the number of amps that can be produced.

If you go for MPPT, then wire size is important.

You are correct 12 Ga is way too small abandon it. I think this is the most important obstacle that you will have to overcome with RV Solar. Just in case you haven't seen these sites before I have included some links:
http://www.amsolar.com/
http://nooutage.com/vdrop.htm
http://www.where-rv-now.com/Notes/Solar/index.php#Calculator
http://www.rvsolarelectric.com/index.php?route=directory/directory&directory_id=3
http://www.jackdanmayer.com/rv_electrical_and_solar.htm

805gregg wrote:
It should be pre-wired for solar, contact Lance support

Thanks....The factory wiring is a concern I have. I have read that it is only 12 gauge wire and is pretty long. I'm afraid of having too much drop with multiple panels.

It should be pre-wired for solar, contact Lance support