<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body><div><div style="font-family: Calibri,sans-serif; font-size: 11pt;">Why wouldn't you invest in an I-V curve tester like the Solmetric PVA series and let it do the heavy lifting of the testing you are looking for?<br>Or am I missing something in what you are looking for?<br><br>Sincerely,<br>Glenn Burt<br>Sent from my 'smart' phone so please excuse grammar and typos.</div></div><div dir="ltr"><hr><span style="font-family: Calibri,sans-serif; font-size: 11pt; font-weight: bold;">From: </span><span style="font-family: Calibri,sans-serif; font-size: 11pt;"><a href="mailto:frenergy@psln.com">frenergy</a></span><br><span style="font-family: Calibri,sans-serif; font-size: 11pt; font-weight: bold;">Sent: </span><span style="font-family: Calibri,sans-serif; font-size: 11pt;">10/4/2015 21:56</span><br><span style="font-family: Calibri,sans-serif; font-size: 11pt; font-weight: bold;">To: </span><span style="font-family: Calibri,sans-serif; font-size: 11pt;"><a href="mailto:re-wrenches@lists.re-wrenches.org">RE-wrenches</a></span><br><span style="font-family: Calibri,sans-serif; font-size: 11pt; font-weight: bold;">Subject: </span><span style="font-family: Calibri,sans-serif; font-size: 11pt;">[RE-wrenches] PV testing</span><br><br></div>Wrenches,<br><br> As time passeth, we're bumping more into older PVs/arrays that have <br>questionable outputs. After minimizing the variables (dust, temps, sun <br>angle, wiring, expected deterioration with age, etc) and still coming up <br>with low numbers. Testing individual PVs' Voc and Isc don't seem to tell <br>the whole story as they often look good.<br><br> Would not a definitive test be to wire a suspect PV to an <br>inexpensive mppt CC (oxymoron?) and then to an orphaned battery. The <br>battery would have to have a mondo (surplus) rheostat paralleled to it to <br>maintain a steady voltage during the test. With appropriate metering in <br>place, you would then have Vmmp and Immp as the rheostat is tweaked to hold <br>a steady batt voltage and the CC finds the knee.<br><br> Help me here. I know its a little spendy to cobble up but the value <br>of nailing an offender might be worth it. Am I missing something? Is it <br>common for inverters to fall off in output gradually?<br><br>Bill<br>Feather River Solar Electric <br><br><br>_______________________________________________<br>List sponsored by Redwood Alliance<br><br>List Address: RE-wrenches@lists.re-wrenches.org<br><br>Change listserver email address & settings:<br>http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org<br><br>List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html<br><br>List rules & etiquette:<br>www.re-wrenches.org/etiquette.htm<br><br>Check out or update participant bios:<br>www.members.re-wrenches.org<br><br></body></html>