Solar panels in series December 16, 2009, 02:37:37 am Yahoo Message Number: 108573Rich Gort said: voltage the panels can come up with above that needed to charge the battery (not counting component and cabling loses, about 13+ volts) and convert it to the proper voltage needed to charge the batteries.> That would seem to be unnecessary. It is my understanding that a MPPT controller is really just a DC to DC converter, and even a lower voltage input from poor sunlight (say 5-7 volts) could still be converted to enough voltage to charge the battery. Since Watts is Watts, two panels together in parallel or in series would seem to operate about the same. Since you have the panels, you could set them up on the ground and wire them up both ways. With the higher voltage controller, some metering and various sunlight conditions you could tell us which really works best. Curious to find out, Ron and Bluebelle, a '99TKB[Non-text portions of this message have been removed]
Re: Solar panels in series Reply #1 – December 16, 2009, 01:23:07 pm Yahoo Message Number: 108585On Wed, 16 Dec 2009, QuoteRich Gort said: > voltage the panels can come up with above that needed to charge the battery (not counting component and cabling loses, about 13+ volts) and convert it to the proper voltage needed to charge the batteries.> That would seem to be unnecessary. It is my understanding that a MPPT controller is really just a DC to DC converter, and even a lower voltage input from poor sunlight (say 5-7 volts) could still be converted to enough voltage to charge the battery. Since Watts is Watts, two panels together in parallel or in series would seem to operate about the same. My understanding is that MPPT controlers only convert voltage downward, converting "excess" voltage into more current at a lower voltage. If you are correct, the advantage of series wiring would be minimal, only making for less loss in the cabling due to lower current between the panels and the controller.Quote Since you have the panels, you could set them up on the ground and wire them up both ways. With the higher voltage controller, some metering and various sunlight conditions you could tell us which really works best. Curious to find out, Ron and Bluebelle, a '99TKB I think that is exactly what I will do. I'll go ahead and purchase the higher Voc controller and try it both ways. I'll be happy to report on what I find.Rich
Re: Solar panels in series Reply #2 – December 16, 2009, 08:02:31 pm Yahoo Message Number: 108598Quote Since you have the panels, you could set them up on the ground and wire them up both ways. With the higher voltage controller, some metering and various sunlight conditions you could tell us which really works best. Curious to find out, Ron and Bluebelle, a '99TKB I've been meaning to ask a similar question but googled other sites first. I came upon this quote from another web site. I'll cut and paste it below."We were all stunned by the results. We repeated the experiment a few times just to make sure we were getting accurate readings. So we cast our shadows across the one panel and then stepped back to allow it full sun several times in a row. The results were100% repeatable every time.(parallel wiring) (series wiring) Full sun 12.8 amps 12.8 amps One panel partly shaded 10.0 amps 1.6 amps Stunning!!! Yikes!!! We generally park in full sun, so we have never really felt a negative impact from this dramatic limitation in our system. However, if we frequently parked in places where a tree branch might shade part of the roof, or if we were putting the panels on a sailboat where the mast, boom, radar mount and sails might shade one or more panels at times during the day, then the series wiring would be extremely inferior to a parallel setup"
Re: Solar panels in series Reply #3 – December 16, 2009, 08:08:18 pm Yahoo Message Number: 108599Sorry Seems I can't get the columns to line up straight in my previous post.
Re: Solar panels in series Reply #4 – December 16, 2009, 08:16:09 pm Yahoo Message Number: 108600The information outweighs the format, by far. Can anyone verify this?__ From: EdwardA wstended@...> Sorry Seems I can't get the columns to line up straight in my previous post.[Non-text portions of this message have been removed]
Re: Solar panels in series Reply #5 – December 17, 2009, 12:46:42 am Yahoo Message Number: 108601Quote From: George Peters To: lifewithalazydazerv@yahoogroups.com Sent: Wednesday, December 16, 2009 6:16 PM Subject: Re: [LD] Re: Solar panels in seriesThe information outweighs the format, by far. Can anyone verify this?Well, it is the way solar panels, at least crystalline ones, respond to shade - - it pretty much turns the cell affected into a resister, shutting down almost all the output from the solar panel. (Remember that the solar panel is typically constructed of a number of cells in series - - so shading a cell is like inserting a resister in series with all the other cells on the panel.) With two panels connected in parallel, shading one panel still leaves the other panel providing output. So the tests make sense.bumper
Re: Solar panels in series Reply #6 – December 17, 2009, 08:20:38 am Yahoo Message Number: 108604Quote From: George Peters To: lifewithalazydazerv@yahoogroups.com Sent: Wednesday, December 16, 2009 6:16 PM Subject: Re: [LD] Re: Solar panels in seriesThe information outweighs the format, by far. Can anyone verify this?Well, it is the way solar panels, at least crystalline ones, respond to shade - - it pretty much turns the cell affected into a resister, shutting down almost all the output from the solar panel. (Remember that the solar panel is typically constructed of a number of cells in series - - so shading a cell is like inserting a resister in series with all the other cells on the panel.) With two panels connected in parallel, shading one panel still leaves the other panel providing output. So the tests make sense.bumper Ok, then why would someone prefer to use "series" for connecting the panels? What is the benefit? I understand one benefit is smaller gauge wire between the panels and the charge controller. Anything else?Ed
Re: Solar panels in series Reply #7 – December 17, 2009, 10:10:20 am Yahoo Message Number: 108610"it is the way solar panels, at least crystalline ones, respond to shade - - it pretty much turns the cell affected into a resistor, shutting down almost all the output from the solar panel... So the tests make sense." Yup. And that kills the attractiveness of the series-connection idea, as far as I'm concerned. One little shadow, anywhere on any panel, and the whole system's output drops to a trickle. Now, if you were mounting panels on a stationary frame in a treeless yard, you might ignore this behavior. But on an RV roof, with its shadow-casting air conditioner housing, vent covers, and multiple antennas... and when you're going to be camping in wooded campgrounds... the "shadow shutdown" effect would be a killer. Well, this has certainly been educational. Now we know why it's not done that way (in serial, that is).Andy Baird http://www.andybaird.com/travels/
Re: Solar panels in series Reply #8 – December 17, 2009, 10:33:33 am Yahoo Message Number: 108611QuoteOk, then why would someone prefer to use "series" for connecting the panels? What is the benefit? I understand one benefit is smaller gauge wire between the panels and the charge controller. Anything else? Rather than smaller gauge wire, likely choice would be same gauge with less power loss over the run. Since the current would be half with a series connection, and voltage drop is current X resistance, voltage drop would be less. Since power is voltage X current, halving the voltage AND current drops the power loss by a factor of 4. HOWEVER, as I mentioned before, panel current output is what translates to the power delivered by the panel (panel output current is directly proportional to insolation), NOT the voltage, so little sun - little power. An MPPT can only maximize available power, it cannot get you what isn't there to begin with in low-light conditions.Steve
Re: Solar panels in series Reply #9 – December 17, 2009, 12:47:35 pm Yahoo Message Number: 108612Quote Well, this has certainly been educational. Now we know why it's not done that way (in serial, that is).Andy Baird http://www.andybaird.com/travels/ I'm with you Andy. I'm in the east with plenty of shade trees etc. However at least one person in the southwest did connect his panels in series. That why I'm curious if there is any advantage to series over parallel.
Re: Solar panels in series Reply #10 – December 17, 2009, 12:49:32 pm Yahoo Message Number: 108614On Thu, 17 Dec 2009, EdwardA wrote:QuoteI've been meaning to ask a similar question but googled other sites first. I came upon this quote from another web site. I'll cut and paste it below.Quote "We were all stunned by the results. We repeated the experiment a few times just to make sure we were getting accurate readings. So we cast our shadows across the one panel and then stepped back to allow it full sun several times in a row. The results were100% repeatable every time.Quote(parallel wiring) (series wiring) Full sun 12.8 amps 12.8 amps One panel partly shaded 10.0 amps 1.6 amps There is no doubt that in this scenario parallel outshines series. That's why we are so carefull about where we mount our panels, avoiding any shadows from other roof mounted stuff. But if one of the panels has shaded cells and the other is in the clear, parallel is definitely the better method. I'm curious if they ran any other scenarios on this web site you found...like low light conditions and how the two methods performed. I'm beginning to think what I will do is wire my panels with a switch to go between the two methods of wiring so that I can choose the best option under any conditions with the flip of a switch.Rich
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