Yes, it is a poor design. though you may not have any problems there with the heat de-rating of the panels. If the panel temperature gets under about 40C you may blow out the input. As long as you have a load on the output of the contgroller, it will keep the voltage down, but if the output is disconnected the input could go up to full voltage.
Who designed such a system? .................................................................................................. Northern Arizona Wind & Sun - Electricity From The Sun Since 1979 Online Store: http://store.solar-electric.com/ Solar Discussion Forum: http://www.wind-sun.com/ForumVB/ .................................................................................................. ----- Original Message ----- From: Walt Ratterman To: 'RE-wrenches' Sent: Friday, June 26, 2009 3:22 PM Subject: [RE-wrenches] Solar Boost Controller in Senegal Hello, I am in a very remote part of Senegal, (near the Guinea and Mali borders…) and I have come across some prefabricated “plug and play” American made systems installed for educational institutions. The systems use two Sharp panels that are 220Watts, 33.6 Voc, 29.2 Vmp, wired in series, using #10AWG home run wire from the panels back to the charge controller. Charge Controller is a Solar Boost 50. Batteries are Dekka AGM – two strings of 250AH, 12V batteries. (four batteries total). My specific question is about the controller. This is a 24V in / 24V out charge controller with MPPT. I have not used this before, so I am not familiar with the details of operation. The data sheet that I downloaded says that the maximum open circuit voltage is 57 VDC. But, this system is hitting the charge controller with two panels of 33.6 VDC wired in series for 73.2VDC. So, why is the controller not fried, or what am I seeing wrong here. I suppose with the panel temperature being elevated maybe 35 degrees above 25 degrees and a resulting 17.5% loss, coupled with some voltage drop, the system may actually be seeing less than the 57 volts. But…..isnt this a dangerous way to design a system? (it will get cooler here ….) Or am I missing something? What would be the appropriate application here…. Sorry, I cant do a lot of internet research from here – limited download capability on the satellite…. Thanks!! Walt Walt Ratterman SunEnergy Power International 11 Laurel Lane South Washougal, WA 98671 (360)-837-3680 ▪ fax (360)-837-1315 ▪ Skype Walt-Mobile wratter...@sunepi.org ▪ www.SunEPI.org __________ Information from ESET NOD32 Antivirus, version of virus signature database 4193 (20090626) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ------------------------------------------------------------------------------ _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
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