2oldman - yes, that 115W Ebay panel is apparently a bad one. All the factors mentioned (heat, dust, long cable) still affect the output, but all these factors combined can't reduce the output from 6.7A to 3.8A.
mike-uswest wrote: I have asked questions before on why I don't seem to be getting as much power out of my panels as I expected. I finally ran a test that tracked down the problem. I covered all of the panels at mid day and the Blu-sky 2000 read .01 amp. Than I uncovered each one alone to see what they were producing. My 53 watt panels were 2.6 and 2.7 amps, rated at 3.2 amps. My 75 watt was 3.8 amps, rated 4.4 amps. Which with them being flat on the roof, 8 gage wire, and daisy chained with long runs, is good I thought. My 115 watt e-bay buy, that I didn't test when I got it, mainly because I wasn't sure how to, didn't fair so well. It is rated at 6.7 amps, and it is producing 3.8 amps. It looks fine, and I think the attachment is good, but it is the first in the string, and has about 15 feet to the next panel, so I don't know if that would affect it. If not what causes them to not produce the expected output? The next question: if I do replace this panel with one a little larger, because I have some room, and since it isn't producing, I would be gaining quite a bit, the other panels are 16.7 and 17.0 volts at load. How close do I have to stay to this output, and will it really make much difference? I wanted to stay with the 12 volt setup, so near the 17 volt output. I was thinking 130-140 watt size. Thanks.
Mike
You have a 3 amp panel in a daisey chain with a 6 or 7 amp panel? How can you expect that to work? It s not the panel's fault it can only put out 3 amps.
I have a similar situation, a pair of 120 watt panels, pair of 45 watt and a single 75watt panel. I could have run them at 24 volts, but have to run them at 12 volts because of their dis-similar capacity.
I might try running the pair of 120 watt in series for 24 volts, and then pair up the 45 watt at 12 volts and then the 75 watt inline to make 150 watts at 24 volts, and see if I get a significant enough increase in voltage to get more amperage out of the system, but because I barely can ever se up what I am making now, I have not tried it.
Anyway if you put all of your panels in parallel, they should all produce 12 volts (nominal, actual voltage under load is about 16 - 19 volts), and it should work normally.
MrWizard wrote: all his panels are parallel,the 115w is Not daisy chained in series with anything
it is simply not performing correctly
Thank you for the ideas on the controller, as you said, the one panel just isn't carrying it's load. It probably doesn't make any difference the way it is usually used, but I was hoping that there was something like a poor hookup that might be the cause, instead of me just buying a dud as usual.
Mike
2003 Dodge 2500 CTD, 4X4,
1994 Alpenlite 26'fifth wheel
See picture in profile.
well you could disconnect the panels and test them one at a time
I would short circuit test the 115w at the roof connections before giving up on it
if it tests OK , then look for the problem
leaving them all connected and covering them, leaves them in the circuit,
if a panel does not have reverse blocking diodes it will drain power from the panel producing power,
thing is the bad panel should effect all panels and since all panels checked better (percentage wise) than the 115w it appears to be under performing
what is the voltage spec on the 115w panel?
* This post was
edited 07/05/12 08:04am by MrWizard *
MrWizard wrote: well you could disconnect the panels and test them one at a time
I would short circuit test the 115w at the roof connections before giving up on it
if it tests OK , then look for the problem
leaving them all connected and covering them, leaves them in the circuit,
if a panel does not have reverse blocking diodes it will drain power from the panel producing power,
thing is the bad panel should effect all panels and since all panels checked better (percentage wise) than the 115w it appears to be under performing
what is the voltage spec on the 115w panel?
The panel is a SunWize SW115. Watts-115, Vmp-16.7, Imp-6.89, Voc-21, Isc-7.65. I am not the most electrically literate, just a little better than being able to turn on a switch, but when you short circuit test the panel, do you just test across the wires to see the DC voltage that it is producing with the meter? I will probably be taking all of them off the roof so a new rubber roof can be put on, so I will need to do all of this then. The only problem is that I have a lot of trips planned through the summer, and will have to fit it in sometime between. With my 2000E, I do have the temperature probe, and set it at 14.8 volts before it starts clicking, so if I set the other pot up all the way, will that overcharge the batteries to the point of boiling out the water? I really do appreciate all of the help. I don't want to get in over my head money wise, the new roof is going to do that with no problem , but I would like to check out my options. Thanks.
short circuit test is for AMPS
you need a meter with a 10amp range
you set the meter on 10amps and you grab the positive and negative leads of the solar panel with the Meter leads
you run the panel power thru the meter,
you only need to do this for few seconds ,just long enough to read the meter and see what the panel can put out
it must be a meter with a 10amp option, usually a seperate socket/jack for the positive lead and clearly labeled
MrWizard wrote: short circuit test is for AMPS
you need a meter with a 10amp range
you set the meter on 10amps and you grab the positive and negative leads of the solar panel with the Meter leads
you run the panel power thru the meter,
you only need to do this for few seconds ,just long enough to read the meter and see what the panel can put out
it must be a meter with a 10amp option, usually a seperate socket/jack for the positive lead and clearly labeled
Also, if you have two meters, you can attach the second meter to measure volts across the solar + and - terminals under load(the first meter is the load). Harbor Freight $3 meters will do these tests.
I would be interested to know the voltage reading for the suspect 115W panel. I am guessing it may have voltage problems as well.
If you would like some suggestions on tests, I have done a lot of driveway tests before mounting my panels.
Multimeters: $3-$4 from China, come under many different names, all have the same circuit board inside and identical looking controls outside. Free shipping from Ebay. Harbor Freight must be the same unit. Horrible cr-ap. Some people order 2, because reject rate is about 50%, no QC to speak of. The other 50% will either not last long or will produce inaccurate readings.
Get Greenlee DM40 or DM60 from Amazon. At $25 it is MUCH better. I would say this is half-way between Ebay cr-ap and professional units like Fluke for $100.
I have a good meter, and a cheap Harbor Freight one, and I just found that my neighbor has a good clamp on DC amp meter for when I get the panel off and can run some tests on it. If it is going bad, is this a slow process, or is it on it's way out soon? The fellow that is going to do my roof is still gone, so my time frame is still up in the air. I hate that.
Offline
, but I would like to check out my options. Thanks.
