Solar charging with some shade

pianotuna wrote:
bfl13,

There are usually 3 strings of cells with 3 diodes.

It seems to vary how many diodes and sections there are. ISTR my Sharp 130w had two. My Sun panels had just one. But the big 24 has 3. However the K 135 seems to say it has 8! Here is what they say they do:

11. BYPASS DIODES
Partial shading of an individual module in a source circuit string (i.e. two
or more modules connected in series) can cause a reverse voltage
across the shaded cells within the module. Module output current is
then forced through the shaded area by the remaining illuminated cells
and other PV modules in series with the partially shaded module(s).

The current forced through the shaded cells within the PV module (or
modules) causes additional module heating and severe loss of power.

The purpose of bypass diodes is to provide a low-resistance current
path around the shaded cells, thereby minimizing PV module heating
and array current losses.

The KDxxxSX-UFBS series modules employ bypass diodes that have:
? Rated Average Forward Current [IF(AV)] Above maximum system
current at highest PV module operating temperature.
? Rated Repetitive Peak Reverse Voltage [VRRM] Above maximum
system voltage at lowest PV module operating temperature.

So the shading causes loss of "power" which is from loss of voltage in the VA, since the amps rating does not go down with heat.

Here is more:

http://electrialstandards.blogspot.ca/2015/07/bypass-diode-function-in-solar-panels.html