Salvo
California
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Joined: 06/01/2008
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Yep, there's a problem. It could be:
1. a panel
2. controller
3. wiring
You need to test the short circuit current of each panel individually. Connect an ampmeter directly to the outputs of the panel. Angle panel into the sun. The current should be 7 to 8 A.
Report back for further instructions.
Sal
CJW8 wrote:Something does not seem right.
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CJW8
Arizona
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Joined: 10/18/2007
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Landyacht
Quote:What is kind of neat about this system is it keeps an amp hour number produced from the only the solar, but not any other charging sources.
I pass all charging sources and loads through the shunt. During this test, Solar was the onlu source.
Quote:As long as all the loads flow through the Shunt, the Trimetric should be accurate to within 10% and probably less. Do you have any wires going to the batteries(-) besides those which come directly from the shunt?
I'll double check that.
Quote:Does the Trimetric have a procedure where you reset the "current Shunt Zero"?
I don't know what this is so I don't think so. It reads zero when I disconnect the frame ground. I can and did reset the total AH to zero bedore starting the test. This number totals negative AH while you are using and then counts back up to zero when you are charging.
Quote:Instead of using the voltage as a 50% SOC mark, you should let the Trimetric determine that by counting amp hours. The batteries can reach 12.3 while under load. That does not necessarily mean they were only 50% SOC unless they rested at 12.2 for many hours after that load was removed.
I only let the batteries rest for about an hour. They were at 11.9-12.0 and bounced back up to 12.3 in an hour. I will rest then longer next time. This one has always neen a hard one for me. In the winter in the morning and the heater and some lights are on, I'll see in the low 11's and think Yikes! Then it bounces back up to 12 when the furnace cycles off.
I agree and I expected the power (watts) to be closer to 270 at noon.
Thanks for your response,
2004 F350 PSD FX4 SB CC, Banks Cold Air Intake, Banks 4" turbo back exhaust
18,000 Superglide
2003 37SP Forest River Sierra Toyhauler (40')
2008 Polaris RZR
405 Watts of Kyocera solar panels, Rogue 3024 Charge Controller
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CJW8
Arizona
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Joined: 10/18/2007
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Salvo wrote:Yep, there's a problem. It could be:
1. a panel
2. controller
3. wiring
You need to test the short circuit current of each panel individually. Connect an ampmeter directly to the outputs of the panel. Angle panel into the sun. The current should be 7 to 8 A.
Report back for further instructions.
Sal
CJW8 wrote:Something does not seem right.
OK, I can do this. My Fluke is good to 10 amps.
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landyacht318
Near a large body of water
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Joined: 07/11/2007
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Here is a link to a site that states the likely output of all brands of panels.
True SP ratings
Scroll to the very bottom and read the fine print, then find your panel in the alphabetical list
It basically says a K 135 panel will likely output 122.2 watts.
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addco
SF Bay Area
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Joined: 04/24/2008
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CJW8:
I don't think there's anything really wrong with the numbers your seeing....
Consider that the Kyocera 135 watt panel produces a "real world" 122 watts. (see post by landyacht318.) That's 122 watts at the panel's maximum power point of 17.1 volts. 122 watts divided by 17.1 = 7.13 amps. Since you're using a non-MPPT controller, the most you will get is 7.13 amps at whatever voltage the panel is operating at. (In your case 13.5 volts at noon.) So the BEST you could hope for is 13.5 x 7.13 = 96.3 watts (at noon). Now consider that by noon, your batteries are approaching 60% charged, and the voltage is starting to rise, so they are not accepting all the amperage they would if they were fully discharged. Also figure in losses due to sun angle on the flat-mounted panels (even at noon) and any dust on the panels, IR squared losses in the wiring, temperature of the panels at noon, etc..
So, 5 amps per panel is a pretty good output all things considered.
Do the same test on a cold, clear winter's day with your batteries fully discharged, your panels tilted toward the sun, and you would see something closer to 7 amps per panel.
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liborko
Surrey, B.C.
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Joined: 02/27/2006
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The reason you don't get 135W from a 135W panel is quite simple: it has to do with the way the panels are rated.
To get 135W from 135W panel, the following conditions must be met:
1. The panel must receive 1000W/m2 amount of light
2. The panel must be operated at V pm and I pm
The condition 1 is easy to fulfill when sun is perpendicular to the panel in bright sunlight
To fulfill condition 2 is little more complicated. To better illustrate what is going on, look at the spec sheet of 123W Sharp ND-123UJF panel
Sharp 123W panel specs click ND-123UJF
Rated power: 123W
Open circuit voltage: 21.8V
Voltage at maximum power: 17.2V
Current at maximum power: 7.15A
Short circuit current: 7.99A
We will consider only one of the three power curves; the one with highest peak and illumination of 1000W/m2.
As you can see from the graph, the current curve stays at close to 8A all the way from 0V(dead short) to about 12.5V where it starts going down and at 21.8V(open circuit) the current is 0A.
At the maximum power, the curves peak, the voltage is 17.2V and the current 7.15A for a total power of 17.2V*7.15A=122.98W. THE POWER THE PANEL IS RATED AT IS A PRODUCT OF VOLTAGE AND CURRENT AT THE POINT WHERE PRODUCING THE HIGHEST NUMBER.
From the plot it is also easy to see that when this panel is connected directly to a dead battery with 10.5V terminal voltage, the panel will supply 8A of charging current at 1000W/m2 illumination. It is also easy to see from the plot that when this panel is connected to a battery with 17.2V terminal voltage, the panel will supply full power of 123W with a current of 7.15A when illuminated by 1000W/m2 amount of light. In other words, to get 123W out of this panel, the panel must work into the precise load at 17.2V&7.15A. This cannot happen with a simple charge controller that connects the panel directly to the battery. In this case the power is 12V*8A=96W. With a Maximum Power Point Tracking (MPPT) type controller the panel is loaded to such a point where the voltage is 17.2V and current is 7.15A for a power of 123W. The MPPT circuitry then converts the extra volts into extra current much the same way the transformer does it for AC. The name for this device is DC to DC converter. So the output current from the MPPT controller is actually higher then 8A,the maximum the panel can supply, under ideal conditions as high as 30% more.
The bottom line: to get anything close to rated output from a solar panel you MUST use a MPPT controller.
Another aspect visible from the plot is that the panel would be capable of destroying the battery by pushing about 7A at 17.5V into fully charged battery unless the charge controller would prevent it.
* This post was
last
edited 05/19/10 12:21am by liborko *
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pianotuna
Regina, SK, Canada
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Joined: 12/18/2004
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Hi liborko,
The Blue Sky converters the DC into high frequency AC, transforms it down in voltage, then reconverts to DC.
Regards, Don
Kustom Koach Class C 28'5" 256 watts solar, 875 amp hours in two battery banks 12 volt batteries 2500 watt inverter.
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CJW8
Arizona
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addco wrote:CJW8:
I don't think there's anything really wrong with the numbers your seeing....
I was thinking that exact same thing. My thought was to keep the panels covered until noon and then uncover them and see what the panel output is. Or, have the batteries at a lower state of charge before starting the test.
Liborko, good reply also thanks. My original goal was to build a system for around $1000. This did not allow a MPPT contorller. It seems to me for a 2 panel system, it is about a wash, economically and electrically, to get a 3rd panel or go with a MPPT controller. After I use this system for awhile, if I have too much gen time than I may shop for a MPPT controller.
If you are installing a 40 panel system, then it is not even a choice economically, you go with MPPT.
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liborko
Surrey, B.C.
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Yes pianotuna. That is exactly what a DC to DC converter does.
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Golden_HVAC
Fulltime, CA, USA
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Joined: 08/19/2003
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me2 wrote:Where did you get your solar isolation (sp?) meter from ?
I found the paperwork on my solar meter.
www.daystarPV.com
Sorry for the delay. It was $144 and $6 shipping.
It reads 50 to 1,200 watts per square meter, 4 digit LCD display. runs on a 9 volt battery.
Fred.
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