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Author Topic: Low cost panels - anyone know about these?  (Read 564 times)

Frank B

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Low cost panels - anyone know about these?
« on: May 11, 2017, 08:11:32 PM »
I have found several references to these panels on the Internet from several different suppliers, some ranging to less than $100 per panel.  At 32" wide, I can put 7 of them on my 30' TT.  They are 38v panels, that should work well with an mppt controller.


Even if they lasted less than 10 years, most of us don't keep our units longer than that anyway.



Thoughts?


Frank.
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1.2 kw solar

Kevin Means

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Re: Low cost panels - anyone know about these?
« Reply #1 on: May 12, 2017, 02:04:33 PM »
Hi Frank. Wow! That's a lot of solar. Do you have a battery bank that could store that much power? Here are a few other things to consider... Unless you were able to mount those panels above your vents, AC unit(s) and other rooftop obstructions, I think you'd have a pretty bad shading problem. At 62" X 32" those panels are physically larger than many (but not all) solar panels that are typically used on RVs. Installing panels that large on a 30' RV roof will likely mean that they have to be mounted very close to vents, AC shrouds etc., and that means that they'll get shaded. If even 2 or 3 solar cells get shaded, it reduces the panel's output to, essentially, nothing, and it does the same thing to any other panels that are wired in series with it. It's because of the way solar cells are wired.

Another thing to consider is the panel's output. Those Topoint 190 watt panels are rated at 36.5 volts, with an amp output of about 5.5 amps at max voltage. When it comes to RV solar, it's all about replenishing amps, not voltage. By comparison, a 100 watt Renogy solar panel puts out about 20 volts and about 5.5 amps, yet it's only about 3/4 the size of the Topoint solar panel, and it weighs only half as much. It also costs about $25 less than the Topoint panel.

Will the Topoints work...? Yes, but IMO, they're better suited for grid-tie solar systems than for RVs.

Kev


2011 Winnebago Tour 42QD
Towing a Jeep Rubicon Unlimited LJ or an Acura MDX
RVI Brake 2, Minder TM-66 TPMS, 970 watts of solar
(Can't wait to spend more time RVing)
Lakeside, California

Lou Schneider

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Re: Low cost panels - anyone know about these?
« Reply #2 on: May 12, 2017, 03:22:56 PM »
A Maximum Power Point Tracking (MPPT) controller converts excess voltage into current, so a 36 volt 5 amp panel will deliver the same power into the batteries as a pair of 18 volt 5 amp panels (10 amps).

Kevin does have a valid point about shading.

With 72 cells and an open circuit voltage of 43 volts, the entire panel is a single series string.  Unless it includes bypass diodes around each solar cell, shading even a single cell will interrupt the output of the entire panel.

If the panel does have bypass diodes, you'll only lose the voltage from the shaded cells, i.e if 4 cells are shaded the output voltage will drop by 2.4 volts at essentially the same current.
« Last Edit: May 12, 2017, 03:33:26 PM by Lou Schneider »

Frank B

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Re: Low cost panels - anyone know about these?
« Reply #3 on: May 12, 2017, 04:15:53 PM »
Kevin:

Thank you for your input.  I have come to respect your opinion greatly.

I am the guy that posted this thread.  I was looking specifically to use high wattage and high voltage grid panels with an mppt controller.  With the boom in grid solar, the price on these panels is coming WAY down, so the price/watt is very good.  I thought I was good with the standard 39.somethingorother inch width of these panels.  However, after having a closer look, they will be too wide to physically fit, regardless of shading.

Quote
If even 2 or 3 solar cells get shaded, it reduces the panel's output to, essentially, nothing, and it does the same thing to any other panels that are wired in series with it. It's because of the way solar cells are wired.

True.  However, as mentioned in the above-linked post, there may be dollars and cents advantages to using  high-voltage low-cost grid panels -- even if some get shaded.  If I use 72 cell high voltage panels, I don't have to put two  in series.  Shading will only affect that panel, not two.  Therefore, I lose (at face value) 190 watts, not 320 like you would.

As to 'too much' solar for the batteries, if the total price is lower, does that really matter?  If I 'waste' solar capacity, I am only wasting sunlight, which is free.  IIUC, with a 'too big' array, I should actually gain on cloudy days in diffuse light.

I spent a very frustrating few hours this morning calling various solar companies around North America.  I get the impression that few really understand well.  They just repeat what they have been told (or have heard).  It is such a new industry that there is little (that I have found, at least) that is independently verifiable.  Instead, there are 'gurus' that have their particular beliefs.  Sure is tough to make an informed decision.

The hangup for me now is shipping costs.  NO ONE in Canada carries the smaller 5" cell grid panels, so I have to buy them Stateside. All I can get here are the 6" cell 39" panels.  Northern Arizona Wind and Sun stocks the 5" x 72 cell panels  at $162.50 each.  Six of them (which I have more than enough room for) would run $1137.50 for an 1140 watt array.

I just checked the cost of the Renology 100 watt panels, and they are $139 each.  Assuming I would lose some of my 1100 watt grid array to shading some of the time, lets compare that to an 800 watt array of Renology panels.  IIUC, putting two panels in series doubles the voltage, but does not change the total wattage (though the mppt controller will produce some current muliplication).  I would need 16 of them to get 800 watts.  16 x $139 = $2112.  That is about double the 72 cell panels I am looking at.  Please correct me if my math is wrong.

Even if I went to 160 watt 6" cell 18 volt panels (similar to what you use), those are about 27" x 60"  Not a long way off from the 5" cell high voltage 72 cell panels at 31 x 63".  And those I don't have to put in series.

So, honestly, I dunno.  I'm getting tired of chasing this.  At $441.09 to ship 6 panels from Northern Arizona Wind and Sun to Calgary, plus duty and brokerage fees, I'm thinking that I may wait till next year and just go to Flagstaff and buy them direct.

However, that is several months away, so I am still open to being reasoned with.  :)

Thanks.

Frank.
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06 GMC 3500 Duramax crew/long pulling 2010 Arctic Fox 30U with 1700 lb Reese Titan Class 5.
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Kevin Means

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Re: Low cost panels - anyone know about these?
« Reply #4 on: May 12, 2017, 06:46:34 PM »
Hi Frank, yeah I remember your post. Let me clarify a couple things, just in case I wasn't clear (My brain and typing fingers aren't always synced well.) A solar panel's watt rating is determined by how many watts it can produce in one hour, under ideal conditions, which of course doesn't happen very often. A panel's watt rating (if you will) is never going to change, only the actual output of the panel will change, depending on the amount of sunlight the panel gets, the solar angle, the temperature, clouds, dirt on the panel etc.

I like to work in terms of amps, because we're ultimately trying to put amps back into our batteries. Fortunately, panel manufacturers also provide us with their panel's amp ratings, but like a car's EPA gas mileage rating, you rarely ever see what's promised. I only threw the 100 watt Renogy panels out there as an example. Personally, I'd go bigger, but not so big that shading would become a problem. Larger panels aren't just more likely to have shading problems, they're heavier, they make it more difficult to work on the roof and the solar cells themselves are exposed to significant stresses when traveling down the road.

You would not need 16 100 watt panels to get 800 watts. You'd need eight 100 watt panels operating under ideal conditions to get 800 watts in one hour. Realistically, we know that we're not going to see ideal conditions very often - especially up north. The sun is just too low in the southern sky as you move north. I know you guys like KOFA as much as we do, and we'll often have near perfect conditions when camping there in the winter, so it can happen. You can compensate for less than perfect conditions by: adding more solar panels; tilting your panels toward the sun, or both. Neither will help much on a cloudy day, but we'll take what we can get.

In our case, every two panels are wired in series, which means we have three sets of two panels. The normal output voltage of each panel is about 21 volts, so each set of panels are putting out roughly 42 volts. You can see that in the picture below. You'll also notice that the panels are pretty dirty.The voltage would actually be somewhat higher had they been clean. So as you said, the voltage is doubled, but their amp output remains the same at roughly 8.5 amps per panel.

The reason our system is wired like that, is because the tech people at Outback told me that my FM-80 controller is most efficient at converting volts to amps when the input voltage is between 40 and 44 volts. That's right where we are with two of our panels wired in series. However, it wouldn't make any difference at all if those 42 volts were coming from a single larger panel. The MPPT controller would still convert the excess voltage to amps. As I've mentioned earlier, however, oversized panels can cause us more than just shading problems.

Our 160 watt panels are 58" X 26" and while two or three inches may not seem like much, it can actually cause real problems when trying to avoid shading on an RV's roof. In the "before" picture below, you can see how the AC units throw some pretty significant shade as the sun begins to set in late afternoon. It was a real challenge to shoehorn six 160 panels onto my roof and avoid that shading. As it is, a couple panels do get shaded in January (when I'm facing east/west) but only after about 3:30 PM, which isn't a problem, because there isn't much solar charging at that hour anyway.

For what it's worth, I'm not at all convinced that the way our panels are wired is any better or worse than if they were all wired in series. I've seen several installations where people with identical setups did just that, and they're getting almost identical performance out of their panels. It's obviously your call if you want to accept a certain amount of shading, but it really does reduce a panel's output significantly. I hope I've helped.

Kev
2011 Winnebago Tour 42QD
Towing a Jeep Rubicon Unlimited LJ or an Acura MDX
RVI Brake 2, Minder TM-66 TPMS, 970 watts of solar
(Can't wait to spend more time RVing)
Lakeside, California

Frank B

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Re: Low cost panels - anyone know about these?
« Reply #5 on: May 13, 2017, 10:54:39 AM »
Lou:

Quote
If the panel does have bypass diodes, you'll only lose the voltage from the shaded cells, i.e if 4 cells are shaded the output voltage will drop by 2.4 volts at essentially the same current.

How does one determine if a panel being considered has that feature or not?

Thanks.

Frank.
Linux:  Free, open, elegant.
06 GMC 3500 Duramax crew/long pulling 2010 Arctic Fox 30U with 1700 lb Reese Titan Class 5.
1.2 kw solar

Frank B

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Re: Low cost panels - anyone know about these?
« Reply #6 on: May 13, 2017, 11:15:02 AM »
Kevin:

Quote
I hope I've helped.

You always do.  I just don't always listen like I shoiuld.  :-)

I can see where putting unshaded solar on your MH was a bit of a challenge alright.  Those 3 tall a/c units called for special consideration, and the offset to the one Maxair vent didn't help.

The roof on our unit is simpler, as I have one fairly low-profile a/c more or less in the middle of the unit, and the 3 Maxair vents are down the center line of the trailer rather than being offset.  Keeping the unit warm is more of an issue for us than keeping it cool as we seldom travel in the summer.  Too many people on the road and in the campsites for my taste.  My own yard is quieter in the summer than the campgrounds!  :)

OK, if 800 watts is achievable from just 8 100 watt panels regardless of how they are connected, then the cost aspect is about even (if I allow for a 25% loss for possible shading) whether I use high voltage or low voltage panels.  And, as you state, the shading is more of an issue early and late in the day when solar tends to drop off anyway.

I can't afford the shipping on the panels that started this thread, so I will either have to go with something more like you have that I can buy locally, or wait until next winter when we hope to be in Arizona again.  Should I go with the 72 cell panels, I can buy them and pick them up myself in Flagstaff, and then install them at a friend's winter home in Casa Grande.  We never buy much when stateside anyway, so our duty exemption for being out of the country for more than 4 weeks should cover most of that as well.  And I won't have to pay a customs broker.  :)

So, I'll mull this over some more....

Now, you also mentioned somewhere that you went with the Outback controller over the Morningside unit on another's recommendations.  What tipped the balance for you?  The Outback seems to have a pretty smart way of dealing with the absorption stage from what I have read, and I was leaning toward it.

Finally, do any of these controllers buzz or whine while they do their work (aside from a cooling fan)?  I have limited options as to where I can install one that will get cooling, but will not be exposed to the elements.  And a lot of that will depend on the dimensions of the device.  A wide flat one may suit me better than a boxy one.

Thanks again for the input.  I really do appreciate you taking the time to 'hand hold' me on this.

Frank.
« Last Edit: May 13, 2017, 11:17:43 AM by Frank B »
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Kevin Means

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Re: Low cost panels - anyone know about these?
« Reply #7 on: May 13, 2017, 02:42:29 PM »
It's no trouble at all Frank, and I hope we can hook up at KOFA early next year, so you can show me your setup. Yeah, I had to have my panels shipped to me too - ordered them through Home Depot. Not exactly "off the rack" items.

I went with the Outback controller for a couple reasons. They, like Morningstar, had a solid reputation. Outback also had an 80 amp controller, whereas Morningstar only had a 60 amp controller. That may have changed, so you should check if you're interested in buying a Morningstar. The FM-80 has a cooling fan vs. just cooling fins, and when you're running that many amps through a controller, a fair amount of heat is going to be generated.

In all honesty, I think a good quality 60 amp controller would probably work just fine for solar arrays of 1000 watts or less. The most amps I've ever seen from my 970 watt array is 52, and that was on a sunny day last May. I just wanted a bit of padding. The FM-80 is a pretty big device - probably 18" X 6" X 5", so make sure you've got room for it if that's what you're going to go with. Outback also makes a 60 amp controller that's a bit shorter, but it doesn't have a cooling fan.

Our controller is installed in a basement compartment, about three feet from the batteries, and when I'm sitting outside on a quiet day, I can hear the fan kicking on and off. There's no electrical whine or other noise at all, just the cooling fan. It's a computer fan, so it's pretty quiet. The fan only runs when the FM-80 is doing its thing. When it goes to sleep each night, it's silent.

Both Morningstar and Outback make remote panels to monitor, log and control the devices. (Outback calls theirs the "Mate.") I chose not to get it, because once you've got the controller programmed, that's pretty much it. There's no need to keep reprogramming it.

Instead, I installed a Trimetric RV 2030 battery monitor, which performs some of the Mate's monitoring functions. It also does an awesome job of letting you know the status of your battery-bank at all times. It's one of the most useful boondocking tools I've ever purchased.

Kev
2011 Winnebago Tour 42QD
Towing a Jeep Rubicon Unlimited LJ or an Acura MDX
RVI Brake 2, Minder TM-66 TPMS, 970 watts of solar
(Can't wait to spend more time RVing)
Lakeside, California

Frank B

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Re: Low cost panels - anyone know about these?
« Reply #8 on: May 16, 2017, 12:22:58 PM »
Lou:

Never got an answer back from you on determining whether a panel has bypass diodes or not.  However, I may have stumbled across it in the specs on another panel, the GoSolar or Solartec S72MC panel, which is a 205 watt panel of the same 32 x 62" dimensions. 

On the  attached PNG in the specifications box, subheading "Connection" it shows IP65 junction box with 3 bypass diodes.  Does this mean that the panel is divided into 3 independent regions, and if one is shaded, the others continue to work (at less voltage)?  I have seen specs on this panel that shows 6 bypass diodes as well, depending on where/when you buy it.

Thanks.
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Frank B

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Re: Low cost panels - anyone know about these?
« Reply #9 on: May 16, 2017, 12:45:03 PM »
Kevin:

Quote
It's no trouble at all Frank, and I hope we can hook up at KOFA early next year, so you can show me your setup. Yeah, I had to have my panels shipped to me too - ordered them through Home Depot. Not exactly "off the rack" items.

Yeah, us too.  Hope we can do it again this coming year.  With the Canadian dollar being as low as it has been in a LONG time, it is getting pretty expensive to go, however.  One Canadian dollar is now worth a whopping 72 cents US.  :(  I thought it was bad at 75 cents this past winter!

Quote
In all honesty, I think a good quality 60 amp controller would probably work just fine for solar arrays of 1000 watts or less. The most amps I've ever seen from my 970 watt array is 52, and that was on a sunny day last May.

My thoughts are the same.  Outback claims their 60 amp unit will do that all day long at temps up to 104 degrees.  While an 1100 watt array could perhaps produce more than 60 amps on a good day in bright sunlight, I don't need that much to keep our batteries charged in good weather.  I would like an oversize array for 'grey' days, of which we had many this past winter. 

I am assuming that  once the controller reaches its max, it will just stop drawing more available power from an oversize  array anyway, 'wasting' some of the sunlight.  Though I will have to check with the manufacturer to be sure that one cannot 'redline' and fry it with a too big array.

I still don't know for sure where I am going to install the controller.  There are not a lot of options in our unit that are close to the fridge cavity where I am likely going to have to bring the wires into the trailer from the roof.  The fridge is also very close to the 60 amp converter, so I hope to use that existing trailer wiring for the solar array's connection to the batteries as well.

I just posted to Lou Schneider again with regard to bypass diodes.  Have a look and let me know if I have this right.

Thanks again.

Frank.
Linux:  Free, open, elegant.
06 GMC 3500 Duramax crew/long pulling 2010 Arctic Fox 30U with 1700 lb Reese Titan Class 5.
1.2 kw solar

Frank B

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Re: Low cost panels - anyone know about these?
« Reply #10 on: May 21, 2017, 06:02:17 PM »
Kevin,


Well, I bit the bullet and ordered six 205 Watt 72 cell panels from ameresco. They also are sending me an 80 amp Outback controller, one very similar to what you have. I paid to have them shipped, despite the horrible cost. :-(  However, I would rather install them at home slowly during summer, than have to do it in a few days at a friend's place while on vacation next winter.  I don't like having to work while on vacation, and all of my tools and my garage are here.


I know that you used UV resistant wire directly on the roof of your motorhome. Have you ever thought about, or do you have any experience with outside plastic conduit for the wiring? That is more or less a standard product, with standard clips, attachments, and junction boxes.


Frank.
Linux:  Free, open, elegant.
06 GMC 3500 Duramax crew/long pulling 2010 Arctic Fox 30U with 1700 lb Reese Titan Class 5.
1.2 kw solar

AStravelers

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Re: Low cost panels - anyone know about these?
« Reply #11 on: May 22, 2017, 05:22:11 PM »
It may be to late for you to change the shipping to have the freight company hold the panels at the freight terminal and you go pick them up.  You could save $200-400 by not have the freight company bring the panels to your house on a lift truck.  Of course you would have to have a trailer or truck to haul the panels.  The freight company will only pick up and place the pallet on your truck or trailer.  No special handling.  Or they could just put the pallet on the ground and you move the individual panels to the truck/trailer.

I used this shipping method for my two 325 watt panels and saved a couple hundred dollars.  My panels are about 72"x60". 
Al & Sharon
2006 Winnebago Sightseer 29R
2009 Chevy Colorado 4X4

http://downtheroadaroundthebend.blogspot.com/

Frank B

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Re: Low cost panels - anyone know about these?
« Reply #12 on: May 22, 2017, 05:37:58 PM »
Thanks for that. I don't have the shipping confirmation yet because of the long weekend here in Canada. I will definitely pursue that option!
Linux:  Free, open, elegant.
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AStravelers

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Re: Low cost panels - anyone know about these?
« Reply #13 on: May 22, 2017, 06:29:08 PM »
Frank,

Even if you are very knowledgeable about electric and RV electric systems the following website is chock full of useful info about RV batteries, Solar wiring, etc, etc.  Well worth reading.   Not that you should do every thing he recommends, but the website is very informative.

http://www.jackdanmayer.com/rv_electrical_and_solar.htm
Al & Sharon
2006 Winnebago Sightseer 29R
2009 Chevy Colorado 4X4

http://downtheroadaroundthebend.blogspot.com/

John From Detroit

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Re: Low cost panels - anyone know about these?
« Reply #14 on: May 23, 2017, 09:07:51 AM »
FOund a company at Hamfest last friday.. I think this is their URL.. Interesting and reasonablly priced

http://www.powerfilmsolar.com/
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Kevin Means

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Re: Low cost panels - anyone know about these?
« Reply #15 on: May 23, 2017, 12:45:45 PM »
Hi Frank. Sorry, I just noticed your question. I don't have any experience using the conduit you mentioned on the roof of an RV. I don't see why it wouldn't work, as long as it would hold up against the elements. The 8 gauge stranded UV stuff I used was fairly pricey, and somewhat difficult to work with. (Thick strands) Fortunately, I only had to make a few bends.

The MC4 connectors found on most modern panels were designed to accommodate up to 10 gauge wire, but the guy who helped me with my installation (Bob Shearer) said you could stuff 8 gauge wire into them if you "encouraged them" a bit. 8 gauge wire is a little better than 10 gauge wire at reducing voltage loss as wire runs get longer.

When I was shopping for junction boxes, I discovered that not all of them were made of UV protected material. That's definitely something that needs to be sealed and UV protected. And FWIW, I ended up building my own terminal bus inside the junction box. I couldn't find one with an adequate number of terminals, that was laid out suitably for my wiring. 

Kev
« Last Edit: May 23, 2017, 01:43:10 PM by Kevin Means »
2011 Winnebago Tour 42QD
Towing a Jeep Rubicon Unlimited LJ or an Acura MDX
RVI Brake 2, Minder TM-66 TPMS, 970 watts of solar
(Can't wait to spend more time RVing)
Lakeside, California

HueyPilotVN

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Re: Low cost panels - anyone know about these?
« Reply #16 on: May 23, 2017, 03:45:04 PM »
Kevin,

I know that you used UV resistant wire directly on the roof of your motorhome. Have you ever thought about, or do you have any experience with outside plastic conduit for the wiring? That is more or less a standard product, with standard clips, attachments, and junction boxes.

Frank.

Frank,

I used flexible plastic conduit on the wiring for the security cameras and solar cable on the roof of my coach to protect the wiring.  I also wrapped it with electricians tape.  I am sure that it cannot hurt and does protect the wiring.

I got the plastic conduit at my favorite tool store for about $3 each.
« Last Edit: May 23, 2017, 03:53:39 PM by HueyPilotVN »
Bill Waugh
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