

Eric,

Your production numbers don't seem that unreasonable to me, comparing actual
numbers with STC. That said, there may still be a problem.

We just repaired 4 - BP SX150S modules. The owner said they were, "about 10
years old". These had a 1 inch x 4 inch x 1/2 inch encapsulated / potted
termination point for the two pigtails and three bypass diodes. The original
soldered connections between the pigtails and the module busses were bad, as
well as at least one of the diodes.

It turned into a bear of a job. At first I thought the MC3 connectors were
faulty, because flexing them caused open circuit voltage fluctuations on our
meter. It was actually the movement of the pigtail at it's module connection
point causing the problem. 

To make a long story short, we used a Dremel tool with a burr bit to remove the
potting material, allowing us access to the diodes and soldered terminations. We
ultimately bit the bullet and just replaced all twelve diodes and resoldered
everything. Interesting, fussy and time consuming. They work fine now. This is
an offgrid, 48 Volt system, with the modules in series pairs. Might better have
been a warrantee event, but by that time I had cut off the MC3 connectors, and
figured it would be an uphill battle with BP. 

Makes a person wonder how many deployed modules have diode / soldering issues,
and also think about the wisdom of moving away from module junction boxes,

Dick Ratico
Solarwind Electric 


--- You wrote:
Hello Wrenches,

I am helping a client troubleshoot a complaint about underproduction of his
on-grid system installed about 6-8 years ago. At first I thought I might
encounter the bad Kyocera KC120 issue but it turns out they have BP170's, 40 of
them for an STC power rating of 6.8kW. 

Ratings of the BP modules: PTC=150.7, Vmp=35.4, Voc=44.2, Imp=4.8, Isc=5

The system has four panels of ten modules wired in series for a nominal rating
of about 350v, 4.8a per string.

At the DC disconnect (first accessible combiner) I measured: All strings right
at about 375v(oc), 4.7a(mp). After the strings are combined, at the DC input of
the SB6000 (with the AC power to the inverter OFF) I measured about 375V as
expected. Once the AC power is connected, the SB6000 starts up, and MPP
operation is initiated, the DC voltage drops to about 280V, and amps sit between
14 & 15A.  I didn't think the voltage was supposed to drop upon MPP
tracking...especially this much. This voltage drop would account for the
observed power loss between actual and rated production values. I'm going to
check with SMA but I wanted to ask the experts here too, as someone may advise
something like, "Oh yeah, BP modules have a similar defect as the Kyocera..."

My questions:

Is the DC voltage supposed to drop significantly in MPP mode on these inverters?
If not, does this indicate a bad inverter?
Anyone know of problems with BP modules manufactured around 2006-2008?

The Kyocera modules showed good volts and amps until a load was connected. Seems
like a similar issue here.

Eric Stikes
SunHarvest Solar
--- end of quote ---

