Help configuring an old Seimans panel J box

[littleharbor]

So I bought an old grid tie system that is composed of 66 Seimens SP75 panels and a Trace SW 5548 inverter with large capacitors insted of batteries. This system will be broken down to individual panels and sold piece by piece. As I'm breaking down the tri-lam , 3 panel modules and getting into the junction boxes I find these panels have been set up in the 6 volt configuratuon. These panels could be wired as 6 or 12 volt nominal. In the junction box there is some sort of electrical component on one of the two + output terminals, bottom left, connecting to one of the two - negative terminals. I have removed it and it can be seen in the top photo of the J box connections. Not sure what it is but maybe a blocking diode.

So my dilema is I cant figure out how to get 12 volt nominal voltage from these panels. I have handled hundreds of these panels in the past and haven't had any issue configuring them for 12 volt output. In the bottom photo I have already set the jumpers for 12 volt. The factory configuration would have bypass diodes on the right and left where I have a solid wire jumper. I can't see the fact that I have solid wire in place of diodes would prevent the panels from making voltage but wired as the lower photo I'm getting 0 volts Even straight off the buss tabbing coming in from the cells. It's a mystery.

Has anybody out there ever seen this Jbox configuration and can possidly point me in the right direction?.

DSCN4562.JPGDSCN4561.JPG

[SunEagle]

I would try to rewire the panel per the 12V diagram. That would include replacing the two hard wire jumpers with diodes and removing the small wire between the + and - output terminals.

For 12 volt you should only need to wire to one of the positive and one negative terminal which is being done by those two wires leaving the j box.

[littleharbor]

I would try to rewire the panel per the 12V diagram. That would include replacing the two hard wire jumpers with diodes and removing the small wire between the + and - output terminals.

For 12 volt you should only need to wire to one of the positive and one negative terminal which is being done by those two wires leaving the j box.

So you're saying that the solid wire, in place of the diodes wouldn't work? I'm thinking the Blocking diode, or whatever it is has something to do with it as I've never seen one before. I have tried to get voltage with, and without the wire in question, nothing.

[bcroe]

Looks like for max voltage, you need to remove the jumper wire running between sides,
and use it to join the center 2 terminals. Bruce Roe

[littleharbor]

Looks like for max voltage, you need to remove the jumper wire running between sides,
and use it to join the center 2 terminals. Bruce Roe

I'm thinking that makes sense. The solid wires in place of the diodes shouldn't be there (maybe) and the center jumper joins the two halves of the cells in series.

[SunEagle]

So you're saying that the solid wire, in place of the diodes wouldn't work? I'm thinking the Blocking diode, or whatever it is has something to do with it as I've never seen one before. I have tried to get voltage with, and without the wire in question, nothing.

No the solid wires will create a circuit for 12v. I sometimes like to start from scratch concerning circuit wiring to identify the issue.

I am not sure why that device (possibly a diode) was wired between the + & - output terminals. It looks like someone took a standard 12v panel and made the modification for a reason.

If you can't get any voltage measurement you may have an internal wiring issue at the cell level.

[littleharbor]

No the solid wires will create a circuit for 12v. I sometimes like to start from scratch concerning circuit wiring to identify the issue.

I am not sure why that device (possibly a diode) was wired between the + & - output terminals. It looks like someone took a standard 12v panel and made the modification for a reason.

If you can't get any voltage measurement you may have an internal wiring issue at the cell level.

These panels came from a working grid connected system. I think Trace designed these things way back then. The previous owner had the Trace Sw 5548 mounted in a trace outdoor enclosure which also had the big capacitors( presumably acting as batteries ) and it was in sell mode selling all power to the grid. He had another back up, enclosed with caps inverter that he said trace had sent him direct.

Thing that kind of seemed weird is that the modules were racked up in sets of three panels and the panels were set up for 6 volt output. I'm thinking the sets of three needed to be series wired with another set of three to have an output of about 51 volts, (6 x 8.5) which would satisfy the 5548's need for voltage.

[peakbagger]

I am surprised the panels are worth much. They are fairly old. That family of panels had a few bad years where the encapsulant got cloudy and pulled away from grid on top of the panels. I have few of them around the house, They still work albeit at a lower output. Most of mine were sold to folks with off grid camps that wanted a little bit of DC power.They also had those funky covers on the junction boxes with the rotating catches that seem to get lost over time.

[littleharbor]

I am surprised the panels are worth much. They are fairly old. That family of panels had a few bad years where the encapsulant got cloudy and pulled away from grid on top of the panels. I have few of them around the house, They still work albeit at a lower output. Most of mine were sold to folks with off grid camps that wanted a little bit of DC power.They also had those funky covers on the junction boxes with the rotating catches that seem to get lost over time.

Sounds like Siemens panels from Germany. I've had some of those in the past. didn't like them. These SP75 panels, at least of the 400 or so I've had , have never had a problem with the encapsulant.

[littleharbor]

I would try to rewire the panel per the 12V diagram. That would include replacing the two hard wire jumpers with diodes and removing the small wire between the + and - output terminals.

For 12 volt you should only need to wire to one of the positive and one negative terminal which is being done by those two wires leaving the j box.

It appears the diodes need to be there as you suggested. Withh solid wire jumpers in place of the diodes I was still getting 0 volts. Rewired j boxes with the diodes and, Voila! Good voltage.

[SunEagle]

It appears the diodes need to be there as you suggested. Withh solid wire jumpers in place of the diodes I was still getting 0 volts. Rewired j boxes with the diodes and, Voila! Good voltage.

I wonder if each section of "cell strings" is wired in reverse so combining them cancels it all out. With the diodes you end up polarizing each "6V string" and then added they get you 12V. Strange way to build a pv panel.

[littleharbor]

I wonder if each section of "cell strings" is wired in reverse so combining them cancels it all out. With the diodes you end up polarizing each "6V string" and then added they get you 12V. Strange way to build a pv panel.

As I get farther into these panels I think I'll have a better Idea. I'll try every configuration with a DVM to figure them out. I only had a few minutes to dig out some diodes and reconfigure a couple panels. One had some serious shorting in it at some time and melted the buss tabbing entering the J box right off.

[SunEagle]

As I get farther into these panels I think I'll have a better Idea. I'll try every configuration with a DVM to figure them out. I only had a few minutes to dig out some diodes and reconfigure a couple panels. One had some serious shorting in it at some time and melted the buss tabbing entering the J box right off.

Sounds like fun. Enjoy your measuring experiments. Stay safe my friend.

[littleharbor]

Sounds like fun. Enjoy your measuring experiments. Stay safe my friend.

One panel at a time No real danger. Just a lot of tedious work.
Thanks

[bcroe]

I thought it was to provide two different voltage options, like 12V or 24V battery charging. That
sort of setup is common on big equipment for say, 240VAC or 480VAC operation. Another
possible reason is for an MPPT option. Bruce Roe