Until I buy a pwm charge controller for my new 12 volt "camping" panel I have a few questions about wiring my 20v and 12v panel's together in series going into the Classic. One is mono and one is poly. I know this is far from ideal since the controller will get confused when trying to find the maximum power point and I'm not sure how the mono/poly comes into play but here are my questions anyway...
1. Will it hurt anything?
2. Will I get more output using the two than using the 255 watt 20v panel alone? I know I won't get anything near what I could with 2 controllers but if I get anything more than the 255 panel alone then it may be worth doing on a temporary basis.
3. What would be the best mode to use to get the best output?
Here are the specs on the panels.
255 watt mono
Voc-37.8
Vmpp-31.4
Isc-8.66
Impp-8.15
125 watt poly
Voc-21.9
Vmpp-17.4
Isc-7.68
Impp-7.11
Stop. You can't wire these panels in serie and use them with a PWM controller. One is 24V nominal, the other is 12V.
A+
Erik
I would be putting these in series into the Classic 150(mppt). The pwm controller that hasn't been purchased yet will be for the 12volt panel only.
If you want to use your 255W 24V Solarworld with your Classic in a 12V system, it has been designed for this use. Wire your 125W 12V panel with another cheap 12V PWM controller and wired both controllers in parallel to your 12VDC batteries.
A+,
Erik
Erik, that is my end goal(1-2 months) but I didn't know if I could run the 2 panels together to the Classic temporarily in hopes of getting output greater than using the SW 255 alone. If not then I'll wait(or order the pwm sooner than later) but I thought I would ask the question.
Don't connect these panels together in serie or parallel. Just connect your Solaworld, that's the best you can do. To connect these panels in serie, they need to be identical or with very close specifications. Wait and buy a cheap 12V controller to connect your other panel (you can find a PWM controller at very low price) or sell it to friend and buy another Solarworld 255W to make your 48V array.
A+,
Erik
I'm not good at waiting so I guess I'll go to plan B, buying the pwm sooner than later. SolarWorld Panel #2 will come in January. I'm going to add 1 per year. Thanks for the responses.
WX,
As Erik is alluding to, the mismatch in Imp is farther off than one would like -- normally it is said that for series connection of PVs, the Imp should be within 5-ish percent. You are close to 15% disparity of Imp. It is quite possible that this series string could yield about as much power as the SW255 alone. But why not run that experiment? PV Power curves are surprisingly "flat" around the MPP, and I'd bet that you would get a bit more from the series string than from the SW 255 alone, but am too lazy to calc it right now.
Whatta I know ??!?
And Erik fine on your modest sized freezer. Where you are, you do not really need a freezer for 5-6 months per year ??
Have Fun, (EA Rules!), Vic
Hi Vic,
Vic, I'm not in the Arctic with frozen ground all the year (for sure, I would like it) ;D.
I'm in ZEC Mitchinamecus, it's a kind of Park close to Reservoir Mitchinamecus in the Laurentians. But 5 years ago, we were living 5 hours north where it was a steady -40°F in january, so didn't need freezer at that time. It was before you can feel climatic changes...
Now, we buy frozen meat for the dogs in December and fight to keep it frozen up to the end of March. As I told you, at this time, solar was at its beginig and Outback or Midnite weren't born. Without guys like boB or Robin, we couldn't live the way we like in nice places where others could not (I'm trying to find my best English).
Vic, why dont you need two large systems? Why don't you buy a battery Monitor?
A+
Erik
OK, Erik,
Yea I did memember you mentioning your early days at the beginning of Solar. I did think that you were still very far north, guess it was my misconception ... perhaps all the dogs that I assumed might have been Sled Dogs -- have not looked at the video yet.
I'll Google your location, and look at your video.
Guess that French is your favorite language? Your English is quite good. Thanks! People like me are SO lazy, we wait for others to learn OUR language!
EDIT: OH, and the two systems are at locations separated by about 1 Km, and about 3 Km of road -- too far to run power between locations.
I actually do have a TriMetric, but have never installed it. A Hydrometer actually is a good BM. Waiting for MN to make a BM or something close ... perhaps a CC reading a Shunt in the Neg lead of the batts.
OK Erik, I will do my homework, Did Google your location ... looks very nice ... lotta lakes. Have Fun, and enjoy EA. I am in town now, so have not had a chance to download the new Classic FW and install it. Cheers, Vic
Hi Vic,
That's what I was thinking but you can't compare hydrometer and BM use. I spend several years without BM and one day I bought one just to see. Now, I think that's definitively the best way to monitor your bank (with hydrometer) and wonder why I've not bought one before.
Agree with you, a CC reading a shunt would be the best but if you have a Trimetric, why not use it? Give it a chance waiting for this MN Cadillac Controller.
A+,
Erik
panels wired in series, limits the amps to 7.1A Voltage would be about 60V, wattage harvested would be 426W STC. or about 340.8w realistically.
Series, amps are limited by the lowest amp panel
Parallel, voltage is limited to the lowest volt panel.
Connecting in series is fine, you are only wasting about 84w STC.
QuoteHere are the specs on the panels.
255 watt mono
Voc-37.8
Vmpp-31.4
Isc-8.66
Impp-8.15
125 watt poly
Voc-21.9
Vmpp-17.4
Isc-7.68
Impp-7.11
Hi Mike,
Well, we do disagree on the output of this string. I THINK that you may have been using Voc ratings of each PV to make your calcs.
We DO agree about the string Imp being limited to that of the PV with the lowest Imp.
The other factor that changes the equation from just using Imp of 7.11 times the sum of the Vmp's of course, is that the PV with the higher Imp -- the SW 255 -- will be outputting HIGHER Vmp, because the current demand is lower than its STC-rated Imp. That was the oblique reference to the breadth of the power curves. This is not a huge factor, but it IS the way I look at the world.
Vic
Hi Vic and Mike,
I'm not a scientific, but the cost of a little SunSaver 10A 12V is $60 CAD, may be $50 in US for this guy to have all the Watts he has paid for... ;)
Not sure it's a good advice to give him to experiment with a brand new classic which has cost 750/850$ for his small 12V system...
Agreed with Vic, I don't understand how 255W + 125W could output 426W, even with a Classic.
Just my opinion,
A+
Erik
Quote from: Vic on July 06, 2012, 07:02:20 PM...Well, we do disagree on the output of this string. I THINK that you may have been using Voc ratings of each PV to make your calcs.
Whoops. You must be right, using Vmp I get 49V @ 7.1A for 347.9watts x .8 = 278W actual harvest with MPPT. I grabbed the wrong numbers.
The MS sunsaver MPPT, is a +$200 controller for 15A
If you promise not to chill the panels too cold, the Rogue 3024 might be enough, but it only has a 60V input limit.
OK, Mike,
Then we do agree on that.
The only other point that I was trying to make, was that the SW 255's voltage will rise above the stated Vmp, because THAT Vmp was for the stated Imp of 8.15 A. The smaller PV will limit the string current to 7.11 A, so the 255 will have a bit higher Vmp.
This was what I was referring to when I said that I was too lazy to calc the String Vmp.
Vic