Sunday, March 3, 2013

Solyndra Art Project Part 3

The one where I go, 'How many of these freaking tubes is it going to take?'

Okay, its a bright sunny day, I added two more tubes for a total of ten tubes, five sets of 2 in a series parallel combination.

Short Circuit Current
Looks pretty good. With the open circuit voltage of 234V that gives me a power of;
P=IV = (234V)(.143A)=33.46W not bad I'm thinking.

With the PS hooked up but no load the numbers look like this.
That's 15.17V on the output of the PS and the array voltage drops to 229VDC.

In the same situation the current is
.0118A Does this itty-bitty current make sense?

If I hook up the SCC the numbers do this....
That's not good I think...The current jumps up to .152A and the array voltage drops to 52VDC.

At the same time the output of the PS is.
What I think this means is that the PS is off and I'm just reading the battery voltage. The power supply has a low VDC cutoff of 127V anything less than this and it shuts off I believe.

To test that somehow the PS was still working at ~50V I unplugged the array from the PS and plugged it into AC mains and got this.
This is with the SCC hooked up...so the PS has no problem running the SCC when its hooked up to AC.

I think this means that the ten tubes are not enough and can not supply enough current to run the SCC. I realized too late that I should of tested the current running to the SCC when the PS was powered by the AC mains. Then I would know how much power it was using.

How Many Freaking Tubes Am I Going To Need?
Apparently ten is not enough...

I disconnected the SCC from the PS and plugged in a 12V 20W halogen light. It would not stay lit. It pulsed. Does anybody have any idea why?

The PS is 75% efficient which means it should have (.75)(33.46W)=25.09W shouldn't that be enough to power a 20W light?

Though, I believe that switching power supplies don't like certain types of loads? When I hooked up a switching power supply to a windshield wiper motor the same thing happened. It pulsed the motor and would not stay on.

I would love any pointers in figuring out how many tubes I'm going to need to do this. It better not be like 20....maybe this is why Solyndra went out of business?

Now I realized the tubes are flat on a table so possible not capturing as much sunlight as possible but still....Arrrrrrgh!

Good News?
I finally figured out the SCC. Turns out if I just did the opposite of what the manual said it worked!
And, I don't need the dark detector! Hurray one last thing.
Now the SCC turns on the load for 4 hours after it gets dark!
Hurray, one goodish thing...

Update
I just realized that there is a logic bomb in my above analysis of the data.
It would be a impossibly bad Solar Charge Controller that let the battery back feed the solar array.
I believe that the  12.65V output of the PS is actually what the PS is outputting.
That the 120VDC min is for the PS to output its rated power.
So at 50V input it outputs 12.65V.
This is slightly encouraging as now I can just add pairs of tubes until the output is say 14V, that should be enough to keep the battery charged no?
Still have to figure out how many tubes I will need to do this.....

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