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Followup on KC120-1 panels not producing power

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Posted by Brian Litzinger on October 28, 2003, 8:08 pm
As you may recall from my previous postings, my SW4048 based system
with 24 KC-120-1 panels has not been producing the expected power.

I have 6 banks of 4 panels arranged as groups A through F.

The various groups tend to produce a rather varied amount of power.
Several around 6.5amps at 53.6 volts, others 3 to 4, one 1.5.

I picked 6 panels and pulled them out of their groups and then
their open voltage in a bright, cloudless, noon time sun.

I kept the panels in the shade.  I then moved them one at a time into
the sun and adjusted their angle to maximize the open voltage reading.

And here is what I got:

Panel measurements
1 19.2
2 19.1
3 18.9
4 19.2
5 19.5 +0.3 -1.0
6 19.2 +0.1 -0.2

The voltage reading would not settle down on 5 & 6.
The ambient temperature was 70 degrees F.

Can someone instill some meaning into these numbers and possibly some
relationship to my varied output by group?


Posted by Solar Guppy on October 28, 2003, 9:33 pm
You should have followed the advice we had suggested earlier ...

Randomly selecting 6 of your 24 panels is NOT a way to debug your problem.

The Strings that have less current have panels that the bypass diodes are
conducting in.

The String voltage will match the load , but since the remaining panels are
being current sourced to a higher (relatively speaking) voltage , the power
produced is less

The banks that produce 6.5 amps are fine.

The banks that produce less need the attention.


1) isolate each group of 4 panel strings
2) you should see a voltage of about 82 volts without load in a moderate
3) On the strings with lower power output you will see a reduced voltage
4) measure each panel in the reduced voltage sting (no need to isolate each
panel , just the string of 4) and you should see about 20 volts across each
5) You should find panels that will read about 10 volts (instead of 20
volts) , these are the panels causing the reduction
6) disconnect the bypass diodes that show a 1 volts across them , then
7) if the voltage increases to normal , you have shorted diodes , you can
get replacements at radio-shack for a buck
8) if the voltage remains drops to zero , there is an issue with the actual
cells/connections internal to the KC-120 , get Kyocera to help in the

BTW: I have seen other KC-120's have the diodes short out ... no big deal to
change the diodes as they are on the screw terminal blocks on the KC120. On
the KC-120 , there are 3 diodes in parallel across each 18 cells, 6 diodes
per panel. Only one of the 3 need to short out to have that half of the
panel disabled/bypassed.

if you follow (and don't skip steps) , you will have found your problem

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