Solmetric has some good screen shots of what happens when you combine these modules. My students just did a lab of combining modules (210W and 175W) in series and parallel and testing the PVA 600. In series V add and current drags way down to the lowest I value in the series string. The IV curve looks so screwy that a MPPT will have a very hard time locating the MPP. In parallel the IV curve looks much more stable. Parralel would be the best way to combine different modules. I can send some photos of the IV curves if you'd like. Jesse Dahl
NABCEP PV Installation Professional IBEW Local 292 - Electrician Electrical/Solar PV Instructor - HCC Sent from my iPhone > On Jun 23, 2016, at 1:17 AM, Dan Fink <danbo...@gmail.com> wrote: > > Dan; rough-and-tumble world indeed here off the grid! My understanding is > that Voc will still be additive, minus degradation over the years, but that > the larger Pmax modules will be current limited for Imp by the smaller ones. > So your 245w modules could only do 100w in the scenario you give. > > My solution has always been just stick with PWM controllers in these > situations. > >> On Jun 22, 2016 10:37 AM, "Daniel Tittmann" <dan...@greenwired.com> wrote: >> In the rough and tumble world of off grid system management for people who >> have been piecing together systems for years it is not uncommon for our >> company to come to a project and find many different types of solar modules. >> In most cases these modules are working fine and producing power but often >> have different output profiles. In an effort to upgrade systems and >> increase production I have often had the idea of building string of these >> different modules and feeding them into an MPPT controller. >> >> Can anyone out there explain if this would be a good idea or a bad one? >> >> Let say we have >> 4 x 100 watt 17.5 Vmp modules >> 2 x 245 watt 30.5 Vmp modules >> >> what would be the outcome of 2 strings of modules >> both with: 2 x 100 watt + 1 x 245 watt >> would this cause issues with the MPPT controller (say OB FM60) or the >> modules? Obviously you need to build strings that will fit the profile of >> the controller and not over to the series string rating and voltage >> tolerance of the modules but from a production standpoint where does this >> land? >> >> thanks for your advice >> Cheers- >> Daniel >> >> >> >> Daniel Tittmann >> CTO >> Greenwired >> www.greenwired.com >> dan...@greenwired.com >> 707-923-2001 (office) >> 707-206-5088 (Cell) >> >> _______________________________________________ >> List sponsored by Redwood Alliance >> >> List Address: RE-wrenches@lists.re-wrenches.org >> >> Change listserver email address & settings: >> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >> >> List-Archive: >> http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html >> >> List rules & etiquette: >> www.re-wrenches.org/etiquette.htm >> >> Check out or update participant bios: >> www.members.re-wrenches.org > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: RE-wrenches@lists.re-wrenches.org > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org >
_______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
