Salvo
California
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I'm sure that had something to do with it. But technically, I don't believe their 44-cell panel was as great as they claimed.
I had done some calculations a while back where a hot 44-cell panel will force the controller out of MPPT mode (just like the 36-cell panel).
It just wasn't a better mouse trap.
Sal
SCVJeff wrote:Most likely it was a battle of economics and supply and demand.
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Salvo
California
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Considering all the time you spend giving solar advice, I suggest you spend more time understanding how solar really works.
pianotuna wrote:
I thought solar panels were constant voltage devices?
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HobbyTalk
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Joined: 08/23/2009
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One thing for sure, the lower cell count allowed them to make a 21" wide 100w panel. That does make putting it between the AC and side wall possible, something that is really not doable with a 26" wide panel.
I've spent hours looking at panel sizes the past couple days. The small size of the AM Solar panels sure are attractive in my case because of the limited space available on the roof. If you consider the cost of watt per square foot of the different brand name panels, the AM panels are really not more expensive. While some with more roof space can consider $$$ per watt, I have to look at watt per sq. ft. if I plan on going over 250w total.
Sold the RV, bought a house in North Fort Myers
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pianotuna
Regina, SK, Canada
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Hi HobbyTalk,
If there is limited roof space I agree higher wattage per foot is "worth the cost" just as it is for MPPT charge controllers.
Regards, Don
Kustom Koach Class C 28'5" 256 watts Unisolar, 875 amp hours in two battery banks 12 volt batteries, 2500 MSW watt inverter.
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Simplygib
Grants Pass, OR USA
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HobbyTalk wrote:While some with more roof space can consider $$$ per watt, I have to look at watt per sq. ft. if I plan on going over 250w total.
Any consideration as to a mounting system that would eliminate the space concerns? E.g., a framework that would allow mounting panels above the a/c unit. If you got panels for $2/watt instead of $4, that's a $500 savings for a 250-watt system, some of which would be eaten up by the added cost of the mounting system, of course.
Unconventional and maybe not practical, I know, but I like thinking about such things.
Gary and Zahra
93 Dodge Ram 250, 5.9L Cummins Turbo Diesel, 5-speed stick
87 SixPac 8' Truck Camper
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HobbyTalk
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Not really unless I would mount them so they are above the AC or go above the skylight or vents.
BUT, I did get a hold of a local alternative energy company. After a bit of talking about my space issue he came up with a less expensive solution. He found a 240w panel at 32v that would fit in the area. If I want to expand later he found some 21" wide 75w panels that would fit between the AC and side of the trailer. They are narrow enough that I should be able to mount them towards the side of the trailer enough to avoid shading by the AC. These are 17 volt panels so if I hook two in series for 34 volts they could be used with the 32v panel. I would lose about 6% because of the 32v panel but that is only about 10w.
With this setup I could get 390w (or 380w with the loss) at about the same cost then the 200w of panels from AM Solar. Also, the higher voltage of these panels will allow a MPPT controller to work better then the borderline 17v of the AM Solar panels.
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mena661
Southern California
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HobbyTalk wrote:
With this setup I could get 390w (or 380w with the loss) at about the same cost then the 200w of panels from AM Solar. Wow, that sounds like the way to go!!
2009 Newmar Canyon Star 3205, Ford F53 V10
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pianotuna
Regina, SK, Canada
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Hi HobbyTalk,
Mixing voltages is not a grand idea. I would go with the 75 watt panels and settle for 300 watts or 375 watts depending on the room they take.
Series installation, unless there are diodes between each cell, means that if just one cell of one panel is shaded the series pairing output drops dramatically.
BTW today in snow I was getting 7.5 amps at 2:00 pm from my system.
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pianotuna
Regina, SK, Canada
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Hi Salvo,
Why not just answer the question, instead of making an impolite remark?
I'd love a web page with a graph that shows voltage vs light intensity. I've not been able to find one.
It is true that output varies with heat, wave length and intensity. The impression I have received is that once there is sufficient light intensity for power generation that voltage almost immediately rises to the panel rating.
I'm often wrong and when I am I admit it.
If you disagree with my advice please enlighten me so I can give *better* advice.
Salvo wrote:Considering all the time you spend giving solar advice, I suggest you spend more time understanding how solar really works.
pianotuna wrote:
I thought solar panels were constant voltage devices?
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HobbyTalk
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In my readings from many web sites, as long as the voltage is within 10% there is no problem in mixing voltages. It is done many times when people upgrade systems, the only downside is that the higher voltage panel gets downgraded to the lower voltage. Yes I know about series panels and am willing to take that into consideration. The upside is that the higher voltages will allow the MPPT controller to work much more effectively then at the lower voltage.
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