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| BlueSky: Newbie question on MPPT http://solar-guppy.com/forum/viewtopic.php?f=5&t=590 |
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| Author: | tbottger [ Thu Nov 15, 2007 8:50 pm GMT EthGMT ] |
| Post subject: | BlueSky: Newbie question on MPPT |
I am looking at buying a couple 140 W panels to keep a couple batteries charged. I am pretty certain of buying a MPPT controller (SB2000E) rated at 25amps. Is it better to get panels with a high voltage and low amps since the MPPT controller will convert the voltage to amps for me anyway, or get a panel that produces more amps and less voltage so the MPPT controller isn't relied upon so much? I am thinking that it would be better to let the MPPT controller do all the work so I can keep my input amps low and thus my wire size smaller. Is that the correct line of thinking or does it matter? |
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| Author: | BB [ Thu Nov 15, 2007 9:06 pm GMT EthGMT ] |
| Post subject: | |
Unfortunately, the SB2000E is not capable of running at higher voltages (two or more "12vdc" rated panels in series)... Their maximum rating Voc is 30VDC. http://www.blueskyenergyinc.com/pdf/SB2000Edatasheet.pdf To do what you want, you need a controller that can manage a much higher Voc voltage. And the higher priced high voltage capable MPPT controllers typically are not that efficient at lower wattages (less than, roughly, 400 watts or so)... Check the specs. at the voltage/current/price you are interested in for the best solution (may be the SB2000E unit--don't know). A drawback with higher input voltages is that the MPPT controllers have switching losses that increase with voltage (per Solar Guppy). It is not a lot (was it 1-2% typically?)--but it is there. -Bill |
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| Author: | tbottger [ Fri Nov 16, 2007 8:17 pm GMT EthGMT ] |
| Post subject: | |
Thanks BB; I didn't look closely enough at the maximum input voltage for the SB2000E. I guess I will maybe look at the SB50. Thanks for you advice. |
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| Author: | niel [ Sat Nov 17, 2007 12:53 am GMT EthGMT ] |
| Post subject: | |
if you won't need more than say 2 or 3 of the 130w pvs then you could use a smaller model like the sb3024i. if you may wish to expand in the future, then a larger model will be worthwhile going for and if you do go with a larger mppt controller, you may find the xw60 or mx60 to be cheaper for the features. do get a battery temperature sensor to track temperature variations on the batteries. |
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| Author: | tbottger [ Sat Nov 17, 2007 5:09 pm GMT EthGMT ] |
| Post subject: | |
Thanks Niel! The SB3024I may be the way to go here since it seems like you can easily interconnect them together if I would need to ever expand (which I don't see a need right now). I would love to get a mx60 or xm60, but I don't think the budget will allow that right now. Thanks also for the tip on the temperature sensor; I was wondering if it was worth it. |
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