28 replies to this topic

[DrJ]

The voltage and amperage depend upon battery charging status, charge controller, sunlight, tilt of panels, etc.
I have seen 14.2-14.4 volts with up to 16 amps at a time.
I have 1x100 watt panel and 2x120 watt panels.
It was July in Southern Idaho.
Batteries were at 60-75% at that time.
I do not tilt my panels.
All flexible and glued to the roof.

My experience has been 5 amps per 100 watts under ideal circumstances is realistic for those type of panels.

[MarkBC]

Most of the variation in power output is from variation in the current (amps) -- based on time of day (sun angle) and other conditions -- clouds, shade, etc.  The voltage varies much less.

 

I've noticed that the voltage is a little lower when the light is vary dim -- in dawn/dusk glow..and I assume there's the temperature effect, dropping the voltage as the temperature increases, but I've never measured that or really noticed that.

Otherwise, the voltage is more-or-less constant throughout the day while the current varies from 0 amps (at dawn and dusk) up to maximum at midday.

 

Temperature effect on voltage:  For polycrystalline silicon panels like mine they say the maximum voltage drops about 0.3% for every increase of 1°F in the panel temperature.  Panels are rated at 77°F...so if my panels were at 100°F then the voltage should be about 6% lower than rated...and they probably get a lot hotter than that.

I wonder how hot my panels get on a typical day?  

Today's temperature is supposed to be in the mid-70s, so "typical".  I think I'll try to measure the surface temperature of the panels using my IR thermometer, and also see what voltage they're putting out at that temperature.

[huskyrunnr]

Renogy RNG-100DB (their 100 Watt Flex panel) has published specs of V_oc = 21.7 V, I_sc = 6.10 A.

 

Cool panel, optimized angle, gave V_oc = 20.7 V. That dropped to 19.7 V after heating up.

 

I_sc on the hot panel was 5.9 A.

 

These values were measured at the mc4 connectors which are about two feet of cable out from the cells. I used two different VOM's but I didn't haul out the Fluke to make measurements.

[Casa Escarlata Robles Too]

Mark,the temp issue sounds interesting. Since the panels are black I would think they get pretty hot. Don't have an IR thermometer ,maybe a meat one would work.

 

Just went outside and using a small meat thermometer I got a reading of about 95*. The air temp is about 65* or so and the panel is in direct sun.

 

While we are on solar.

I just purchased a inexpensive 12V watt meter ($13) from Amazon. The reviews were all good most 5 stars and that was comparing it to some of the higher priced ones.

 

OK so my question is. There is a "source" and "load" side it seems that I have read two different ways to install it. Which side goes to the battery and which side goes to the solar controller?

 

I should get this in a couple days so there isn't any hurry for answers.

 Thanks Frank

[MarkBC]

....

 

While we are on solar.

I just purchased a inexpensive 12V watt meter ($13) from Amazon. The reviews were all good most 5 stars and that was comparing it to some of the higher priced ones.

 

OK so my question is. There is a "source" and "load" side it seems that I have read two different ways to install it. Which side goes to the battery and which side goes to the solar controller?

 

I should get this in a couple days so there isn't any hurry for answers.

 Thanks Frank

 

I'm no expert, but....

Current flows from source to load. If you're wanting to measure the current that the solar controller is feeding the battery then the "source" gets connected to the controller and the "load" to the battery.

 

Does that sound right?

[Casa Escarlata Robles Too]

I'm no expert, but....

Current flows from source to load. If you're wanting to measure the current that the solar controller is feeding the battery then the "source" gets connected to the controller and the "load" to the battery.

 

Does that sound right?

 

I want to see how much the solar system is putting out and what the battery level is.

I think your thinking is right.

BUT is there a WRONG way to hook it up?

I don't want to short or burn anything up.

 

Thanks Frank

[MarkBC]

I want to see how much the solar system is putting out and what the battery level is.

I think your thinking is right.

BUT is there a WRONG way to hook it up?

I don't want to short or burn anything up.

 

Thanks Frank

 

Well, you have to make sure that you're hooking + to + and - to - ...but you probably know that.

I don't know if connecting it in the opposite way from what I suggested above would harm anything or just not provide useful current data.

[Casa Escarlata Robles Too]

Thanks Mark and +to+ good reminder. At our age it's always good for the thought.

Frank

[RC Pilot Jim]

Thanks to IMIX. Worth another look on the first page.

 

Great video on original Post. A "little over the top" though we all get a good idea of what they are.