Did you use the Diode Test function on the meter? If the diode is good you should see around 0.4-0.8 V in the forward bias, and OL in reverse. If it is bad (open) you'll get OL in both directions, and if it is shorted closed you'll get the 0.4-0.8 V reading in both directions.
Shorted closed would be the failure mode that would indicate an always-closed diode providing a permanent bypass path and thus a drop of 25% of voltage per bad diode (or set of paralleled diodes). (These have 4 diodes right?). Brian Mehalic NABCEP Certified Solar PV Installation Professional™ R031508-59 520.204.6639 Solar Energy International http://www.solarenergy.org SEI Professional Services http://www.seisolarpros.com On Thu, Jul 6, 2017 at 4:31 PM, Taiyoko Sadewic < [email protected]> wrote: > Hi Wrenches, > We were installing Sanyo HIT modules back in 2006-2007 and in 2014 we had > a rash of bad Sanyo modules. The modules had distinct voltages below the > good modules ie 50% or 75%. Sanyo at the time (now Panasonic) indicated > that it was a bad diodes from a lightning strike not covered by warranty. > > I finally got around to checking that out. I identified the purportedly > bad diode in one module (four per module) that was performing at 75% and > removed it. The diode appears to be fine using an ohm meter. Is that a > valid test? > > Anyone else have similar findings or experiences with this? Could > lightning blow apart the tab ribbons inside of the module? > > Thanks > > -- > <http://www.PositiveEnergySolar.com> > Taiyoko Sadewic > Employee-Owner > NABCEP™PV Installation Professional > NABCEP™Technical Sales > 3209 Richards Lane | Santa Fe, NM 87507 > cell 505.570.0137 <505.699.9032> > [email protected] <[email protected]> > www.PositiveEnergySolar.com > <http://www.positiveenergysolar.com/> > <http://www.facebook.com/positiveenergysolar> > <https://twitter.com/PositiveESolar> > <https://plus.google.com/+Positiveenergysolar> > <https://www.youtube.com/user/PositiveEnergySolar> > <https://www.positiveenergysolar.com/blog/blog/> > <https://www.positiveenergysolar.com/contact/refer-a-friend/> > <https://www.bcorporation.net/community/sunpower-positive-energy-solar> > <http://www.solarreviews.com/installers/positive-energy-solar-reviews/> > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: [email protected] > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: http://www.mail-archive.com/[email protected]. > org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > > >
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