[RE-wrenches] Shell Solar Warranty?

[Christopher Warfel]

I replaced a system with them.  I think realistically given the price of 
modules, the age of the Shell modules, bless and recycle the Shell 
modules, and replace.  The system owner for this project was astounded 
at how much more energy he had. Off grid system with generator. Chris

On 7/15/2026 5:16 PM, Zeke Yewdall via RE-wrenches wrote:
> If they are at 30% of rated output, is it current or voltage that's 
> suffering at Vmp?  And how does Voc and Isc stack up to rated values?  
> Have you done a IV curve on the actual module, or just measuring the 
> total array?  What sort of MPPT are you using on them?  My experience 
> with old modules is that they are usually still good (80% or better of 
> rated power), or are completely dead (open circuit, no output).  70% 
> loss while not being completely dead seems odd.
>
> I have had an issue with some older 36 cell 120 watt modules, which 
> made it appear that they had precipitously dropped in output, when 
> really it was only about a 10 or 15% drop in Vmp and Voc.  But this 
> was enough for the charge controller to fall off the IV curve, and 
> drop the current by almost 50% just because of the position on the IV 
> curve.  In this case, they were two 36 cell modules in series, 
> charging a 24 volt battery (some configuration that the old PWM charge 
> controller had used) -- the charge controller could not track any 
> lower voltage because it had to stay at battery voltage + a few 
> volts.   So a relatively mild loss in Vmp had resulted in a serious 
> loss in output power due to the MPPT tracking details.  When I rewired 
> them in strings of 6 in series instead of 2 in series, the charge 
> controller was able to maintain tracking on the actual Vmp, and power 
> was at least 80% of rated again.
>
> I have had issues with shorted bypass diodes dropping voltage of some 
> newer modules to 2/3 or 1/3 of rated output.  In my cases, they were 
> usually due to lighting strikes (also took out a bunch of other stuff, 
> and upon repairing the other stuff, we found some strings of modules 
> were not up to rated voltage, and upon testing individual modules, we 
> found a couple of them to be exactly 1/3 or 2/3rds of normal 
> voltage).   A thermal image while the module is under load can 
> identify shorted substrings of cells in a module -- the shorted string 
> will be hotter than the portion still producing power.
>
> And, with some 120 watt Evergreen modules, which had two parallel 
> strings of cells in them, I had issues with a bad internal connection 
> to one of the parallel strings of cells -- which meant that voltage 
> was normal, but current was only half of normal... this was a problem 
> due to being wired in series in other modules that still had full 
> current.  Both Isc and Voc measured where they should for the complete 
> string, but the curve was very much not right.  Measuring individual 
> modules showed that some were only half rated amperage.
>
> Zeke
>
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-- 
Christopher Warfel, PE
ENTECH Engineering, Inc.
PO Box 871, Block Island, RI 02807
(401) 447-5773