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pablo

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Reply with quote  #11 
Quote:
You did not measure the wattage in that test. To measure the wattage you need to take a voltage and current measurement SIMULTANEOUSLY then calculate the wattage. That is why I am directing you towards doing the the short circuit current test with two meters.  

For the sake of clarity, the open voltage wattage is always zero because the is no current in an open circuit. When you switch the meter to current mode it forms a closed circuit.  Because the open voltage is from one circuit and the short circuit current is from another circuit, one cannot use the two to calculate wattage.  


Hey Rick,

My head is starting to spin!  [smile] ... the above two paragraphs sound like they're in conflict.  It is my understanding wattage is volts x amps.  If I use two volt meters in my test, one set to voltage and the other current, won't I see what the controller is seeing?  Or close to it?

Quote:
Elaborate .... which direction do they face, angle from the horizon.


The panels are facing south and because we're typically at the cottage midsummer (we're closing it next weekend), I have the panels angled for roughly between August 1st and September 15th - 36 degrees.

I used an app on my phone to ensure the panels angled properly..

Thx!
-pablo

Rick H Parker

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Reply with quote  #12 

My head is starting to spin!  [smile] ... the above two paragraphs sound like they're in conflict.  It is my understanding wattage is volts x amps.  If I use two volt meters in my test, one set to voltage and the other current, won't I see what the controller is seeing?  Or close to it?


How your asking about a different set of conditions. In the previous test, the panels where in isolation. As soon as you connect the panels to the controller the panel is no longer isolated ... different conditions.

If you measure the current from the panels and the voltage across the panels when it is connected to the controller, calculate the wattage, the calculation should be close to what the panel reading is at that time. You do understand when connected, you measure the current by inserting the current meter between one of power lead from the panels and the corresponding terminal on the controller. You do not short the current meter across the panel as you did in the other test.

Wattage = Volts * Amps ... correct. The current in an OPEN circuit is always ZERO because the is no pathway from current to flow from the positive to negative terminals. Anything multiplied by zero equals zero. Open Voltage is the voltage of a OPEN circuit. OPEN circuit, no current, no power.




The panels are facing south and because we're typically at the cottage midsummer (we're closing it next weekend), I have the panels angled for roughly between August 1st and September 15th - 36 degrees.

I used an app on my phone to ensure the panels angled properly..

Just checking, you said you only need 12V. I realized this might be a mobile install with the panels flat on the roof. That would have explained a low power output.


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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
Rick H Parker

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Reply with quote  #13 

My head is starting to spin!  [smile]

It might stop spinning when you come to realize the reason you're not seeing what you expect to see is because you keep changing the electrical conditions.

When when you switched the meter from volts to current you changed the electrical conditions from open circuit to closed circuit.

When you reconnect the panels to the controller you change the electrical conditions from unloaded to loaded.


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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
pablo

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Posts: 7
Reply with quote  #14 

 

Quote:

It might stop spinning when you come to realize the reason you're not seeing what you expect to see is because you keep changing the electrical conditions.

When when you switched the meter from volts to current you changed the electrical conditions from open circuit to closed circuit.

When you reconnect the panels to the controller you change the electrical conditions from unloaded to loaded. 



Nope, I understand that I have two sets of conditions.  I was simply trying to inject some levity with that statement.  Furthermore, your paragraphs weren't especially clear to me.  I'm not saying you were unclear but rather with my newbie status, they were unclear to me.  Which, made my head spin.

As I mentioned from the onset, I'm a newbie.  I will learn.  I always do.  Embedded in your responses are some keywords I can use to Google.  From that, I should be able to bootstrap myself.  I'll more than likely ping some other folks who are a bit more friendlier.

Thank you for your time.  

-pablo

 

Rick H Parker

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Reply with quote  #15 
I'll more than likely ping some other folks who are a bit more friendlier.

I have not seen anybody here exhibiting hostility ... at least not lately.

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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
stmbtwle

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Reply with quote  #16 
Sorry Pablo

On another topic:

THE WAY I SEE IT (could be wrong) is that your controller responds to voltage as opposed to current, and the voltage is dependent to some extent on state of charge. So when you put a load on the battery, the voltage drops rather slowly as the battery depletes, and the controller output comes up accordingly. There will always be something of a delay between the application of a load and the controller's response. Not all controllers work this way, some use an external shunt at the battery so the controller sees the current and responds immediately. I see no mention of a shunt in your manual.

However there are two ways to hook up your load. Some controllers have only two sets of connections (solar and battery) and the load is connected directly to the battery. There may or may not be provision for a shunt.
YOUR controller also has "load" connections. IF your load is connected to the "load" connections, the controller may be able to sense the load immediately. If it's not, it can't. Heavy loads such as inverters and starters HAVE to be connected directly to the battery, but with lighter loads you have the option. How your load is connected I don't know.

Trying to charge your battery is like trying to push your car to the top of a hill (full charge). The battery (gravity) will fight you every inch of the way. It's not likely you'll ever see calculated power in real life (I don't), and worrying about it WILL make your head spin.

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Willie, Tampa Bay
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