[RE-wrenches] Sanyo HIT module diode issues

[Dave Angelini Offgrid Solar]

The diode check on a dvm is useful but may not show a diode breaking down
at higher voltage. Yes lightning can open up the tabs or connecting foil
inside a solar panel. It can do alot more than that! One of the best
reasons for using an SPD at the array is also preventing the latent damage
that can show up later. A really close strike and prayer may help but I
doubt it :)

Dave Angelini Offgrid Solar
"we go where powerlines don't"
http://members.sti.net/offgridsolar/
e-mail  offgridsolar at sti.net
text 209 813 0060


> 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 Professionalâ„¢ 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 <
> taiyoko at positiveenergysolar.com> 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
>> NABCEPâ„¢PV Installation Professional
>> NABCEPâ„¢Technical Sales
>> 3209 Richards Lane  |  Santa Fe, NM 87507
>> cell  505.570.0137 <505.699.9032>
>> Taiyoko at PositiveEnergySolar.com  <Taiyoko at PositiveEnergySolar.com>
>> www.PositiveEnergySolar.com
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