Author Topic: Panels output not the same  (Read 974 times)

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Basil

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Panels output not the same
« on: June 13, 2008, 11:33:36 PM »
Here I go again. Hope I don't rub some one the wrong way. I know this has been ask. I have even read some on it in the past here but I can't find it now. Question: I have six 15 watt panels. Yea HF. Great for learning. But this could go for any panels. Four read 22 volt open. Two read 17 volts open. Will the two with less volts pull the others down.
« Last Edit: June 13, 2008, 11:33:36 PM by (unknown) »

ghurd

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Re: Panels output not the same
« Reply #1 on: June 13, 2008, 06:22:08 PM »
Usually...

As long as the low V PVs are higher than about 15V, it's OK.  They sometimes make the same amps.  Sometimes they do not.

Open the box if possible.  Check if the screws are tight.  It is a common problem.


Might check all 6 for loose screws.

G-

« Last Edit: June 13, 2008, 06:22:08 PM by ghurd »
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Basil

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Re: Panels output not the same
« Reply #2 on: June 13, 2008, 06:30:46 PM »
Thanks I'll check the connections on the panels. Above 15 volts I'm ok. Git it.
« Last Edit: June 13, 2008, 06:30:46 PM by Basil »

Ungrounded Lightning Rod

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Re: Panels output not the same
« Reply #3 on: June 13, 2008, 07:24:55 PM »
It's really more like "as long as you're above the voltage of the battery plus your blocking diode (if any) you're OK".


Voltage is limited by the voltage of the load in a battery-charging operation.  Current from each panel is limited by the lower of:

 - The rate photons hit the least-illuminated cell / paralleled cell group of the panel's series string.

 - The current that causes the voltage drop in the panel resistance plus wiring resistance to equal the difference between the panel's open circuit voltage (less drop in the blocking diode if any) and the battery voltage.


So on hot days the current will start dropping off at a lower temperature for the low-voltage panels than for the high-volt ones.  But you won't run into any problem other than low charging rate.

« Last Edit: June 13, 2008, 07:24:55 PM by Ungrounded Lightning Rod »