Walt......i believe those controllers will give you an MPPT boost going from 24V nominal in which eqautes to 44Voc in to 12Vnominal out.....in this scenario 57Voc max is sufficient..... The sharp panels you mention series together will exceed the 57Voc and "should" cause trouble for the charge controller.....when? probably varies based on manufacturing batches..... If the system is a 24V battery bank than it doesn't sound like you have a good design and are just lucky that the controller hasn't burned up yet...... If you can reconfigure the system to be a 12V battery bank you could craft a nice system with both panels in parallel and all batteries in parallel and even get the charge controller to give you some MPPT boost especially during the cooler months. That controller based on spec sheet doesn't handle above 24V nominal solar array strings......or roughly 44Voc at STC..... good luck....
-- Sunny Regards, Kirpal Khalsa NABCEP Certified Solar PV Installer Renewable Energy Systems www.oregonsolarworks.com On Fri, Jun 26, 2009 at 3:22 PM, Walt Ratterman < wratter...@sunenergypower.com> wrote: > 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 <http://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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