<div dir="ltr">Bill<div><br></div><div>Performance verification would be your first test that can be done with 2 clamp on meters ( idealy two Power meters like the Seaward Clamp Power Meter ) , ie testing under load knowing the irradiance and cell temperatures and measuring watts in and watts out of the inverter. With that data you should be able to tell if the array is at maximum power point and/or if the Inverter is operating within spec. You should account for irradiance, cell temperature and Light Induced Power degradation ( 1% loss per year unless module manufacturer warranty defines it differently), voltage drop soiling etc...</div><div><br></div><div>IMHO Curve tracers are a huge investment in money and time to learn how to get meaningful information out of them. Also the 3 choices currently available each have limitations that make it hard to decide which is the best solution. That would be my last investment on the list of test tools. Better to invest in a Insulation Resistance Tester and then something like the PV150 tester ( which can also do DC Power measurements).</div><div><br></div><div>Bill</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Sun, Oct 4, 2015 at 6:56 PM, frenergy <span dir="ltr"><<a href="mailto:frenergy@psln.com" target="_blank">frenergy@psln.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Wrenches,<br>
<br>
As time passeth, we're bumping more into older PVs/arrays that have questionable outputs. After minimizing the variables (dust, temps, sun angle, wiring, expected deterioration with age, etc) and still coming up with low numbers. Testing individual PVs' Voc and Isc don't seem to tell the whole story as they often look good.<br>
<br>
Would not a definitive test be to wire a suspect PV to an inexpensive mppt CC (oxymoron?) and then to an orphaned battery. The battery would have to have a mondo (surplus) rheostat paralleled to it to maintain a steady voltage during the test. With appropriate metering in place, you would then have Vmmp and Immp as the rheostat is tweaked to hold 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 of nailing an offender might be worth it. Am I missing something? Is it common for inverters to fall off in output gradually?<br>
<br>
Bill<br>
Feather River Solar Electric <br>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr"><div>William Hoffer <br></div>161 SE Fourth Ave<br><div>P.O. Box 1823<br>White Salmon, WA 98672-1823<br><a href="mailto:bhoffer@sunergyengineeringservices.com" target="_blank">sunengser@gmail.com</a><br><br></div></div></div>
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